fswiki.us - User contributions [en]

Fuel

2025-05-19T19:39:01Z

SpookySimon: /* How it's scored at comp */

[[Category: Internal Combustion]]
The energy needed to propel a combustion vehicle is stored as chemical potential energy in a liquid '''fuel''' that is burned by the [[Engine|engine]]. The fuels available at [[List_of_competitions|US competitions]] are gasoline of octane ratings 93 and 100, and E85. Fuels available in [[List_of_competitions|FS competitions]] are 98RON gasoline and E85 <ref> Formula Student Rules 2020 https://www.formulastudent.de/fileadmin/user_upload/all/2020/rules/FS-Rules_2020_V1.0.pdf </ref>. Fuels and the fuel system are covered in IC.5 of the FSAE Rules, and CV 2 in the FS rules. No fuel additives can be used<ref>(2020).''Formula SAE Rules 2020''(v2.1) Location: FSAEonline. https://www.fsaeonline.com/cdsweb/gen/DocumentResources.aspx.</ref>.
=Chemistry=
==Gasoline==

Although the gasoline readily available in the US, and in US competition, is 5-10% ethanol (check about in other countries), gasoline is typically approached chemically as pure octane.
 
: 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2(g)

If we use atomic weights for carbon, hydrogen, and oxygen, we find that 2 mol of octane is 224 grams, 25 mol of oxygen is 800 grams which comes from 3809 grams of 21 percent air. This yields an air fuel ratio of 17. Since gasoline is not pure octane and air is not exactly 21% oxygen. Experimentation yields the stoichiometric ratio of 14.7 grams of air per gram of fuel<ref><cite id="CITEREFHillierPittuck1966" class="citation book">Hillier, V.A.W.; Pittuck, F.W. (1966). "Sub-section 3.2".''Fundamentals of Motor Vehicle Technology''. London:Hutchinson Educational.ISBN 0 09 110711 3.</ref>. Gasoline sold in America has varying levels of ethanol content varying a few percent around a nominal 10% with no way of knowing what exactly is being offered besides testing<ref>U.S. Energy Information Administration "Issues and Methods for Estimating the Share of Ethanol in the Motor Gasoline Supply" https://www.eia.gov/workingpapers/pdf/ethanol_blend_ratio.pdf</ref>. Usually the 100 Octane gasoline is more consistent in this respect.

==Ethanol==
The ethanol used in competition is E85, nominally 85% ethanol and 15% gasoline,.
=System Design=
==Fuel Storage==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]

The fuel tank design rules can be found in IC.5.2 for FSAE and CV 2.3 for FS.

There are two main compromises that the fuel storage system must navigate. The first is Quantity of Fuel. A car will always be faster with less weight, but cutting too close to the minimum fuel level for your car can lead to disastrous consequences such as running out of fuel or temporary fuel starvation, as well as minor inconveniences such as cg changing with fuel level. The second compromise is Fuel Sloshing. As the car accelerates, the fuel itself can move about in the tank, possibly uncovering the fuel pickup and making the car more difficult to drive. Combatting this usually involves a system of internal baffles as well as tank geometry, but the cost is weight, CG height, and the possibility that you design a tank that prevents the fuel from making it back to the pickup fast enough to supply the engine when needed.

===Volume Determination===
There are two ways to size a fuel tank. The first is to carefully restrict the volume of fuel as to ensure a lighter car. The second method is to ensure the fuel tank has enough fuel to be used during extended drive cycles such as those found on test days. Because refueling a car takes so little time and is generally regarded as a safe practice, the first method is often chosen for combustion cars, while the second is more commonly found in [[Battery_pack|EV batteries]].

The minimum quantity of fuel should be enough to barely finish the endurance race at competition. However, this limits the functionality of the car by limiting run time, and increases the likelihood that you will run out of fuel early. The quantity of fuel used in an endurance competition should be determined by experimental data, but can be estimated based on past usage, or usage of similar teams, or if masochistic, be predicted based on average speed of the vehicle, the track length, and the consumption of your engine.

Below are tables showing average fuel consumption by race finishers in the 2019, 2021, and 2022 Michigan Competitions<ref>https://www.sae.org/attend/student-events/formula-sae-michigan/awards-results</ref>.

{| class="wikitable"
|+ Average FSAE Michigan May Competition Fuel Use [L] by Type
|-
! Year !! 93 Octane !! 100 Octane !! E85
|-
| 2022 || 3.7 || 3.8<ref>Villanova was so efficient that this average becomes 4.2 L without including them</ref> || 5.4
|-
| 2021 || 4.0 || 4.3 || 5.6
|-
| 2019 || 4.0 || 3.9 || 5.5
|-
| 2019 (4 cyl engines) || 4.4 || 4.6 || 5.9
|}

{| class="wikitable"
|+ Average FSAE Michigan May Efficiency Score by Fuel Type
|-
! Year !! 93 Octane !! 100 Octane !! E85
|-
| 2022<ref>2022 is a fascinating year, as the most efficient car (Villanova used almost 1/2 the fuel of the second place car as well as being one of the fastest cars, placing them 14 point ahead). The lowest scoring team above 0 (Ottowa) managed to score a 5.7 which is 20 points below the team just ahead of them. In fact for all three years studied here, no team has been so much more efficient and so much less efficient than these two. Villanova is so far more efficient than any other car on track in the last 10 years that someone uncharitable may be tempted to accuse them of cheating. They averaged 21 mpg around the racetrack.
</ref> || 56.5 || 49.4 || 57.0
|-
| 2021 || 77.2 || 66.8 || 77.3
|-
| 2019 || 59.1 || 62.0 || 66.0
|}

===Fuel Sloshing===
Similar to [[Oil|oil sloshing]], fuel will move around in the tank as the car goes around corners or accelerates/brakes. The design of the fuel tank should reduce this phenomenon. Each team will face different levels of sloshing and some may never encounter a problem. Generalized advice cannot really be furnished here except to consider it.

Internal baffles are a frequently employed solution to this. The baffles can be solid, sometimes made of the same material as the tank itself, or the baffle can be a gasoline-resistant open cell foam that resists the movement of fuel inside the tank.

An alternative to, or in addition to an internally baffled fuel tank is placing an absorbent mat at the bottom of the fuel tank connected to the fuel pickup. Anecdotal evidence indicates that a fuel mat like Holley's HydraMat seem to solve fuel pickup issues for teams of all levels<ref>This is from 3 years of talking to teams during tech inspection</ref>.

===Rigid Container===
Most fuel tanks in FSAE are solid. The important considerations for rigid fuel tanks are mounting and material.

'''Mounting''' 
The most important mounting consideration is to ensure the vibration and torsional forces going through the frame cannot pass through the fuel tank. A stressed fuel tank may fracture and leak fuel. The easiest method to ensure no torsional forces can be transferred into the fuel tank is to only use three points for mounting<ref>This method is recommended by competition volunteers and tech inspectors for teams who fail tech due to this rule</ref>. If the fuel tank is attached by bolted connections, it is necessary to isolate the tank vibrationally. This can be achieved by inserting a rubber washer into the bolt/washer stackup between the frame and fuel tank. If rubber washers are used, ensure that the bolt is not tightened to the point that the connection becomes rigid again.

'''Material''' 
They can be made of sheet metal, or a gasoline resistant plastic or composite.

Metal fuel cells cannot be re-welded after fuel has been used in the fuel tank without cleaning it of any trace of fuel or by welding it in an oxygen free environment.

===Bladder===
A fuel bladder is an alternative to a rigid fuel tank. The bladder will expand and contract with the quantity of fuel inside the tank, with the intent of solving sloshing or fuel pickup issues.


The bladder must be enclosed by a non-flexible container that is rigidly connected to the chassis. The rigid casing is not subject to the same constraints as a rigid fuel tank and may be load bearing. This rigid container means that the fuel bladder is unlikely to be lighter than a rigid container.

==Fuel Lines==

{| class="wikitable"
|-
!|Material
!|Internal Diameter [in]
!|Pressure [psi]

!|Weight [lb/ft]
!|Min. Bend
Radius<ref> Minimum Bend Radius for hardlines is considered to be 2*D if drawn and 7*D if rolled. This is a rule of thumb, YMMV https://www.listertube.com/links/tube-bending-design-guide/</ref> [in] 
!|Supplier
!|Notes
|-
| style="text-align:center; font-weight:bold" colspan="8"|Hard Lines 
|-
|Aluminum
|3/8-1/2 (OD)
|250'''*'''

|
|
|Russell
|[https://www.jegs.com/p/Russell/Russell-Aluminum-Hard-Lines/2861386/10002/-1 link] '''*'''pressure rating is wall thickness dependent
|-
|Aluminum (0.035 wall thickness)
|1/4-5/8 (OD)
|200'''*'''

|for 3/8": 0.043 (.651g/cm)
|
|Summit
|[https://www.summitracing.com/parts/sum-g2538 link] '''*'''pressure rating not specified formally, only mentioned in Q&A with conflicting answers, trust with caution
|-
|Nickel/Copper Alloy (0.028 wall thickness)
|.132-0.319 (__ -3/8 OD)
|unspecified

|for 3/8": 0.012 (.175g/cm)
|
|Summit
|[https://www.summitracing.com/parts/sum-220216-25 link] sold as pressure rated comparable to mild steel brake line
|-
|304 Steel (0.028 wall thickness)
|.257-.319 (5/16-3/8 OD)
|3500

|for 3/8": 0.010 (.156g/cm)
|
|JEGS
|[https://www.jegs.com/i/JEGS/555/635202/10002/-1 link]
|-
| style="text-align:center; font-weight:bold" colspan="8"|Soft Lines
|-
|Nitrile Rubber*
|3/8
|50

|
|
|JEGS
|[https://www.jegs.com/i/JEGS/555/15998/10002/-1 link]
|-
|Nitrile* (Neoprene* cover)
|1/8
|50

|
|
|Dayco
|[http://www.daycoproducts.com/dayco®-fuel-line-hose product details] cannot buy direct
|-
|Buna-N*
|3/16+
|50

|
|1.25
|McMaster
|[https://www.mcmaster.com/gasoline-hose/low-pressure-petroleum-hose-8/ link] yarn reinforced
|-
|Buna-N*
|3/4+
|150

|
|3
|McMaster
|[https://www.mcmaster.com/gasoline-hose/low-pressure-petroleum-hose-8/ link] steel wire reinforced
|-
| style="text-align:center; font-weight:bold" colspan="8"|Braided Lines
|-
|Nitrile Rubber* and Steel
|1/4+
|50

|
|
|Spectre
|[https://www.jegs.com/i/Spectre/865/29225/10002/-1 link]
|-
|Nitrile Rubber* and Stainless Steel
|0.22+ (4AN+)
|1000

|
|2
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3270 link]
|-
|PTFE and Stainless Steel
|0.27+ (4AN+)
|1320

|
|0.75
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3480 link]
|-
|PTFE and Aramid
|0.27+ (4AN+)
|1320

|
|0.92
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3490 link]
|-
|PTFE and Polyester
|0.38+
|305+

|
|2
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3495 link]
|}
<nowiki>*</nowiki> Not compatible with e85<ref>https://www.highpowermedia.com/Archive/elastomer-compatibility-with-ethanol-in-fuel</ref>
===Comparison of Line Types===

{| class="wikitable"
|-
!Quality!!Hard Lines!!Braided Lines!!Soft Lines
|-
|Weight
| || ||-
|-
|Cost
| ||-||+
|-
|Cost Tables (FSAE)
| ||-||+
|-
|Manufacturability
||-|| ||+
|-
|Pressure Capacity
||+*|| ||-
|-
|Reusability**
||-|| ||+
|-
|e85 Compatibility
||+|| ||-
|-
|colspan="4"|
<nowiki>*</nowiki>Depends on wall thickness, see table above

<nowiki>**</nowiki>New design or small adjustments that need to be made
|}

==Filling==
Fuel filling is critical to consider in the system design in three ways: safety, function, and rules compliance.
To ensure a safe filling procedure, common sense should be used to prevent fuel spillage and ease of access. An easy process is a safe one. A rules mandated splash guard can further protect the vehicle, driver, and fuel filling team-mate.
===Filler Neck===
The filler neck has a rules specified vertical height, maximum angle, and internal diameter. Meeting these requirements helps ensure the tank can be filled safely, easily, and will pass technical inspection. Because this is often overlooked in design, and creating a new fuel tank or modifying an existing one is quite difficult on the day of competition, it is recommended to strictly follow rules as written, and to ask rule questions if clarifications are needed.

It is unusual but not unprecedented for a technical inspector to measure the internal diameter of the fuel filler neck, or the vertical height if it is visually unclear. Often in these cases, a gas can of the type used by the fuel filling team at competition is used to ensure that the vehicle can be safely fueled even if the rules are not entirely met. If the rules breach is egregious, the car will likely not be allowed to pass tech even if it may be safely fueled.
===Sight Tube===
There are vertical height and routing requirements to the sight tube. A frequently discussed solution is a clear, fuel resistant plastic used as the filler neck material itself to comply with both filler neck and sight tube rules. The fuel filling team at US competitions ask the teams to not mark the fuel fill line themselves and will mark it themselves at the fuel fill station to avoid incorrectly marked fill levels causing an accident.

==Venting==
The fuel tank is required to be able to vent excess vapor pressure while the car is in the correct orientation, but not allow fuel leaking in the event of a vehicle rollover. A common solution is to purchase or create a custom vented fuel cap. Custom vented fuel caps may be subject to a water leak test during tech inspection.

==Pump and Pressures==
Fuel pressures can be divided into two categories for different applications. Most FSAE/FS teams run fuel pressures under 10 bar, which are classified as ''low pressure''. Low pressure fuel is sufficient for single or multipoint manifold injection. Some teams chasing performance or academic goals may opt for high pressure fuel injection to facilitate direct injection.

Pumps are usually specified to pressures greater than that used by the injectors. A fuel pressure regulator is used in-line to achieve final fuel pressure. Fuel pressure regulators can be blocking (returnless or non-return-style) or bypass (return-style). Returnless fuel injectors have only one input and and one output port allowing for a simpler routing system and thus reducing points of failure. These returnless fuel injectors do need a bypass valve at the pump to relieve pressure. The design of these regulators allows for pressure creep, is more sensitive to debris, and are not able to consistently/accurately read pressure without the engine running<ref>Fuller, David. Light, John. "Quick Tech: Return- vs. Non Return-Style Fuel Pressure Regulators for Low-Pressure Fuel Systems" ''On All Cylinders''. https://www.onallcylinders.com/2017/01/12/quick-tech-return-vs-non-return-style-fuel-pressure-regulators-low-pressure-fuel-systems/</ref>. Bypass regulators can be more expensive and drive more complex routing, but yield more accurate fuel readings, have a longer life, and are easier on the fuel pump.
===Low Pressure===
Low pressure is often the default injection pressure for FSAE as most motorcycle or snowmobile engines run at pressures around 3-3.5 bar <ref>Bacon. "Fuel Pressure Specs". ''600RR.NET'', Mar. 4, 2009. https://www.600rr.net/threads/fuel-pressure-specs.131524/</ref><ref>gixxerkart504. "Fuel Pressure???" ''GIXXER.COM/'', Sep. 22, 2008. https://www.gixxer.com/threads/fuel-pressure.199809/</ref><ref>
Be.St.MX. "2012 yzf 450 fuel pressure, fuel pump symptoms bike wont start". ''Thumper Talk'', Sep. 4, 2017. https://www.thumpertalk.com/forums/topic/1240219-2012-yzf-450-fuel-pressure-fuel-pump-symptoms-bike-wont-start/</ref>. Single point injection or throttle body injection (TBI) is when fuel is injected at the throttle, similar to a carburetor. Most modern fuel systems use multipoint injection or port injection (PI), placing the injectors after the plenum and as close as possible to the engine. This results in fuel being sprayed into the intake ports.
===High Pressure===
In order to run a direct injection setup, fuel pressures need to exceed 10 bar. These extreme pressures force higher safety requirements by rules. The major regulation in FSAE is that fuel lines must be stainless steel hard-line or "Aeroquip FC807 smooth bore PTFE hose with stainless steel reinforcement and visible Nomex tracer yarn". Teams can run something similar if the team gets approval before competition. Any fuel line before the boost pump is considered low pressure and is not subject to the fuel line restrictions.

The fuel rail and it's attachments must be able to withstand maximum force from the fuel line (not including cylinder pressure).


==Injectors==
===Placement===
The injector placement can be divided into two categories: manifold injection or direct injection. Manifold injection is easier to implement as the pressures are lower, rules are less strict, and it does not require modifications to most engines used in FSAE.
====Throttle Body Injection====
Throttle body injection (TBI) or single point manifold injection is the oldest electronically controlled fuel injection. It is analogous to a carburetor in concept but allows much more precise and tunable control. This is uncommon as it is older technology and has less benefits for efficiency than other approaches. Because the fuel is injected so high in the intake, a greater proportion of the fuel is lost to the walls of the manifold so control is less precise.
====Port Fuel Injection====
Fuel Injected into the [[Intake|ports]] or multipoint manifold injection just before entering the combustion chamber. The most common type of fuel injection in FSAE, port injection offers high levels of control at a lower cost than DI.


Injecting fuel into the port can be done when the intake valve is open or when the intake valve is closed. Injecting into the port when the valve is open is colloquially referred to as "poor man's direct injection". There are benefits and drawbacks to each.

====Direct Fuel Injection====


===Classification by Resistance===
====Low Resistance====
Usually 0.5 - 5 Ohm. Also called "peak-and-hold-injectors". From this name you can directly infer the mode of operation. In the beginning the ECU has to give a high current to the valve to open it quickly. This is the peak. Then a lower current is sufficient to keep the valve open. A common ratio of the currents is 4:1.

However, for this the ECU must also have a controller that can supply the different currents. The advantage of this system is that due to the high current at the beginning the valve can be opened very quickly. However, this is no longer necessary nowadays, because even valves with high resistance can provide the necessary flow.
====High Resistance====
Ususally 8 - 15 Ohm. Also known as a "saturated drive injector". These are much easier to control, as only the circuit has to be closed and the resistance of the valve controls the current.
==Critical Fasteners==
All fasteners on the fuel system are critical. Nylon locking fasteners are not appropriate near the engine such as the fuel rail. The nylon will soften and will not retain the nut. Most technical inspectors will not catch this but it's a pain to change and better to just do it right the first time.
=Fuel Strategy=
==How it's scored at comp==
[[File:ImpactofFuelUsageinCompetitionbyType.png|thumb|right|Points per L Fuel used in 2021 Michigan Competition]]
[[File:Fuel 2024 fsae.png|thumb|right|Points per L Fuel used in 2024 Michigan Competition]]

Since FSAE and FS considers how much fuel is used as well as how fast each car goes, the cost of fuel in terms of competition score must be considered. There are many ways to analyze the impact of the fuel usage on the competition score.

Unfortunately, there is no dial on the car that teams can turn to raise or lower their fuel consumption. Other factors that impact fuel use besides Efficiency Event scores are usually prioritized such as engine choice, torque, tuning, etc.

A simplistic, black box analysis using the 2021 Michigan Efficiency Event scores shows that gasoline is worth about 17 points per gallon used, and E85 is worth about 15 points per gallon used. The lap-time of the car has almost no correlation to the efficiency scores<ref>Scatter plot of lap time v efficiency score is easy enough to create. I may add one here if I have time.</ref>.
{{clear}}


==Fuel Choice==
One of the biggest choices fueling system design engineers must make is which fuel to run. Teams with limited resources may find that cost and/or convenience may outweigh all other design considerations. Proper documentation and explanation of these restrictions will prevent this concession to real world conditions from being counted against a team in the design event.

The team must decide whether or not to pursue running E85 before many other fuel system decisions. The octane rating of E85 lies around 100, but specific aspects of the fuel mean it is not a direct replacement. The largest difference is the specific energy. E85 has about 75% of the energy per unit mass that gasoline has<ref>https://dsportmag.com/the-tech/education/getting-tanked-the-e85-files-part-1/3/</ref> so the fuel tank will have to be bigger.

==Efficiency==
===Consumption vs. Thermal Efficiency===
===BSFC===
Brake specific fuel consumption is another way to view efficiency and is used to compare engine efficiency despite size differences<ref> The wikipedia page for BSFC is hilariously poorly written. It's inscrutable and incomplete but has this enormous table of various engine BSFC stats.</ref>. It measures how much fuel is used (in lbs/hr) divided by power (hp). It is usually used to show a map of engine operating points to visualize engine efficiency across load (usually BMEP) and RPM.

'''Calculation'''<ref>“Brake Specific Fuel Consumption (BSFC).” X-Engineer, https://x-engineer.org/automotive-engineering/internal-combustion-engines/performance/brake-specific-fuel-consumption-bsfc/</ref> copying from old school notes so i'll have to add context later -simon

this is for finding fuel consumption (mpg or equivalent) w bsfc chart
{| class="wikitable"
|Pme ||Mean Effective Pressure
|-
|nmot ||Motor speed
|-
|iG ||Gear Ratio (for selected gear)
|-
|isec ||FDR
|-
|rdyn ||Dynamic Radius of Tire
|-
|Vd ||Displacement Volume of Engine
|-
|i ||Constant
|-
|Freq ||Tractive force required
|}

<math> P_{me} = \frac{(2\pi*T_{motor,required})}{(V_d * i)} = \frac{(2\pi)}{(V_d*i)} * \frac{(F_{req} * r_{dyn})}{(i_G * i_{sec})} </math>

<math> n_{motor} = \frac{Velocity*i_G*i_{sec}}{2\pi*r_{dyn}} </math>

be (fuel consumption) usually experimentally determined

<math> B_{time} = \frac{b_e*P_{me}}{\rho_{fuel}} = \frac{b_e*P_{me}*V_d*n_{motor}*i}{\rho_{fuel}} </math>

<math> B_{distance} = \frac{B_{time}}{V} </math>

i = 0.5 for 4-stroke engine

=References=

File:Fuel 2024 fsae.png

2025-05-19T19:35:38Z

SpookySimon:

Fuel

2025-05-19T18:58:33Z

SpookySimon: /* Port Fuel Injection */

[[Category: Internal Combustion]]
The energy needed to propel a combustion vehicle is stored as chemical potential energy in a liquid '''fuel''' that is burned by the [[Engine|engine]]. The fuels available at [[List_of_competitions|US competitions]] are gasoline of octane ratings 93 and 100, and E85. Fuels available in [[List_of_competitions|FS competitions]] are 98RON gasoline and E85 <ref> Formula Student Rules 2020 https://www.formulastudent.de/fileadmin/user_upload/all/2020/rules/FS-Rules_2020_V1.0.pdf </ref>. Fuels and the fuel system are covered in IC.5 of the FSAE Rules, and CV 2 in the FS rules. No fuel additives can be used<ref>(2020).''Formula SAE Rules 2020''(v2.1) Location: FSAEonline. https://www.fsaeonline.com/cdsweb/gen/DocumentResources.aspx.</ref>.
=Chemistry=
==Gasoline==

Although the gasoline readily available in the US, and in US competition, is 5-10% ethanol (check about in other countries), gasoline is typically approached chemically as pure octane.
 
: 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2(g)

If we use atomic weights for carbon, hydrogen, and oxygen, we find that 2 mol of octane is 224 grams, 25 mol of oxygen is 800 grams which comes from 3809 grams of 21 percent air. This yields an air fuel ratio of 17. Since gasoline is not pure octane and air is not exactly 21% oxygen. Experimentation yields the stoichiometric ratio of 14.7 grams of air per gram of fuel<ref><cite id="CITEREFHillierPittuck1966" class="citation book">Hillier, V.A.W.; Pittuck, F.W. (1966). "Sub-section 3.2".''Fundamentals of Motor Vehicle Technology''. London:Hutchinson Educational.ISBN 0 09 110711 3.</ref>. Gasoline sold in America has varying levels of ethanol content varying a few percent around a nominal 10% with no way of knowing what exactly is being offered besides testing<ref>U.S. Energy Information Administration "Issues and Methods for Estimating the Share of Ethanol in the Motor Gasoline Supply" https://www.eia.gov/workingpapers/pdf/ethanol_blend_ratio.pdf</ref>. Usually the 100 Octane gasoline is more consistent in this respect.

==Ethanol==
The ethanol used in competition is E85, nominally 85% ethanol and 15% gasoline,.
=System Design=
==Fuel Storage==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]

The fuel tank design rules can be found in IC.5.2 for FSAE and CV 2.3 for FS.

There are two main compromises that the fuel storage system must navigate. The first is Quantity of Fuel. A car will always be faster with less weight, but cutting too close to the minimum fuel level for your car can lead to disastrous consequences such as running out of fuel or temporary fuel starvation, as well as minor inconveniences such as cg changing with fuel level. The second compromise is Fuel Sloshing. As the car accelerates, the fuel itself can move about in the tank, possibly uncovering the fuel pickup and making the car more difficult to drive. Combatting this usually involves a system of internal baffles as well as tank geometry, but the cost is weight, CG height, and the possibility that you design a tank that prevents the fuel from making it back to the pickup fast enough to supply the engine when needed.

===Volume Determination===
There are two ways to size a fuel tank. The first is to carefully restrict the volume of fuel as to ensure a lighter car. The second method is to ensure the fuel tank has enough fuel to be used during extended drive cycles such as those found on test days. Because refueling a car takes so little time and is generally regarded as a safe practice, the first method is often chosen for combustion cars, while the second is more commonly found in [[Battery_pack|EV batteries]].

The minimum quantity of fuel should be enough to barely finish the endurance race at competition. However, this limits the functionality of the car by limiting run time, and increases the likelihood that you will run out of fuel early. The quantity of fuel used in an endurance competition should be determined by experimental data, but can be estimated based on past usage, or usage of similar teams, or if masochistic, be predicted based on average speed of the vehicle, the track length, and the consumption of your engine.

Below are tables showing average fuel consumption by race finishers in the 2019, 2021, and 2022 Michigan Competitions<ref>https://www.sae.org/attend/student-events/formula-sae-michigan/awards-results</ref>.

{| class="wikitable"
|+ Average FSAE Michigan May Competition Fuel Use [L] by Type
|-
! Year !! 93 Octane !! 100 Octane !! E85
|-
| 2022 || 3.7 || 3.8<ref>Villanova was so efficient that this average becomes 4.2 L without including them</ref> || 5.4
|-
| 2021 || 4.0 || 4.3 || 5.6
|-
| 2019 || 4.0 || 3.9 || 5.5
|-
| 2019 (4 cyl engines) || 4.4 || 4.6 || 5.9
|}

{| class="wikitable"
|+ Average FSAE Michigan May Efficiency Score by Fuel Type
|-
! Year !! 93 Octane !! 100 Octane !! E85
|-
| 2022<ref>2022 is a fascinating year, as the most efficient car (Villanova used almost 1/2 the fuel of the second place car as well as being one of the fastest cars, placing them 14 point ahead). The lowest scoring team above 0 (Ottowa) managed to score a 5.7 which is 20 points below the team just ahead of them. In fact for all three years studied here, no team has been so much more efficient and so much less efficient than these two. Villanova is so far more efficient than any other car on track in the last 10 years that someone uncharitable may be tempted to accuse them of cheating. They averaged 21 mpg around the racetrack.
</ref> || 56.5 || 49.4 || 57.0
|-
| 2021 || 77.2 || 66.8 || 77.3
|-
| 2019 || 59.1 || 62.0 || 66.0
|}

===Fuel Sloshing===
Similar to [[Oil|oil sloshing]], fuel will move around in the tank as the car goes around corners or accelerates/brakes. The design of the fuel tank should reduce this phenomenon. Each team will face different levels of sloshing and some may never encounter a problem. Generalized advice cannot really be furnished here except to consider it.

Internal baffles are a frequently employed solution to this. The baffles can be solid, sometimes made of the same material as the tank itself, or the baffle can be a gasoline-resistant open cell foam that resists the movement of fuel inside the tank.

An alternative to, or in addition to an internally baffled fuel tank is placing an absorbent mat at the bottom of the fuel tank connected to the fuel pickup. Anecdotal evidence indicates that a fuel mat like Holley's HydraMat seem to solve fuel pickup issues for teams of all levels<ref>This is from 3 years of talking to teams during tech inspection</ref>.

===Rigid Container===
Most fuel tanks in FSAE are solid. The important considerations for rigid fuel tanks are mounting and material.

'''Mounting''' 
The most important mounting consideration is to ensure the vibration and torsional forces going through the frame cannot pass through the fuel tank. A stressed fuel tank may fracture and leak fuel. The easiest method to ensure no torsional forces can be transferred into the fuel tank is to only use three points for mounting<ref>This method is recommended by competition volunteers and tech inspectors for teams who fail tech due to this rule</ref>. If the fuel tank is attached by bolted connections, it is necessary to isolate the tank vibrationally. This can be achieved by inserting a rubber washer into the bolt/washer stackup between the frame and fuel tank. If rubber washers are used, ensure that the bolt is not tightened to the point that the connection becomes rigid again.

'''Material''' 
They can be made of sheet metal, or a gasoline resistant plastic or composite.

Metal fuel cells cannot be re-welded after fuel has been used in the fuel tank without cleaning it of any trace of fuel or by welding it in an oxygen free environment.

===Bladder===
A fuel bladder is an alternative to a rigid fuel tank. The bladder will expand and contract with the quantity of fuel inside the tank, with the intent of solving sloshing or fuel pickup issues.


The bladder must be enclosed by a non-flexible container that is rigidly connected to the chassis. The rigid casing is not subject to the same constraints as a rigid fuel tank and may be load bearing. This rigid container means that the fuel bladder is unlikely to be lighter than a rigid container.

==Fuel Lines==

{| class="wikitable"
|-
!|Material
!|Internal Diameter [in]
!|Pressure [psi]

!|Weight [lb/ft]
!|Min. Bend
Radius<ref> Minimum Bend Radius for hardlines is considered to be 2*D if drawn and 7*D if rolled. This is a rule of thumb, YMMV https://www.listertube.com/links/tube-bending-design-guide/</ref> [in] 
!|Supplier
!|Notes
|-
| style="text-align:center; font-weight:bold" colspan="8"|Hard Lines 
|-
|Aluminum
|3/8-1/2 (OD)
|250'''*'''

|
|
|Russell
|[https://www.jegs.com/p/Russell/Russell-Aluminum-Hard-Lines/2861386/10002/-1 link] '''*'''pressure rating is wall thickness dependent
|-
|Aluminum (0.035 wall thickness)
|1/4-5/8 (OD)
|200'''*'''

|for 3/8": 0.043 (.651g/cm)
|
|Summit
|[https://www.summitracing.com/parts/sum-g2538 link] '''*'''pressure rating not specified formally, only mentioned in Q&A with conflicting answers, trust with caution
|-
|Nickel/Copper Alloy (0.028 wall thickness)
|.132-0.319 (__ -3/8 OD)
|unspecified

|for 3/8": 0.012 (.175g/cm)
|
|Summit
|[https://www.summitracing.com/parts/sum-220216-25 link] sold as pressure rated comparable to mild steel brake line
|-
|304 Steel (0.028 wall thickness)
|.257-.319 (5/16-3/8 OD)
|3500

|for 3/8": 0.010 (.156g/cm)
|
|JEGS
|[https://www.jegs.com/i/JEGS/555/635202/10002/-1 link]
|-
| style="text-align:center; font-weight:bold" colspan="8"|Soft Lines
|-
|Nitrile Rubber*
|3/8
|50

|
|
|JEGS
|[https://www.jegs.com/i/JEGS/555/15998/10002/-1 link]
|-
|Nitrile* (Neoprene* cover)
|1/8
|50

|
|
|Dayco
|[http://www.daycoproducts.com/dayco®-fuel-line-hose product details] cannot buy direct
|-
|Buna-N*
|3/16+
|50

|
|1.25
|McMaster
|[https://www.mcmaster.com/gasoline-hose/low-pressure-petroleum-hose-8/ link] yarn reinforced
|-
|Buna-N*
|3/4+
|150

|
|3
|McMaster
|[https://www.mcmaster.com/gasoline-hose/low-pressure-petroleum-hose-8/ link] steel wire reinforced
|-
| style="text-align:center; font-weight:bold" colspan="8"|Braided Lines
|-
|Nitrile Rubber* and Steel
|1/4+
|50

|
|
|Spectre
|[https://www.jegs.com/i/Spectre/865/29225/10002/-1 link]
|-
|Nitrile Rubber* and Stainless Steel
|0.22+ (4AN+)
|1000

|
|2
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3270 link]
|-
|PTFE and Stainless Steel
|0.27+ (4AN+)
|1320

|
|0.75
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3480 link]
|-
|PTFE and Aramid
|0.27+ (4AN+)
|1320

|
|0.92
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3490 link]
|-
|PTFE and Polyester
|0.38+
|305+

|
|2
|Pegasus
|[https://www.pegasusautoracing.com/productselection.asp?Product=3495 link]
|}
<nowiki>*</nowiki> Not compatible with e85<ref>https://www.highpowermedia.com/Archive/elastomer-compatibility-with-ethanol-in-fuel</ref>
===Comparison of Line Types===

{| class="wikitable"
|-
!Quality!!Hard Lines!!Braided Lines!!Soft Lines
|-
|Weight
| || ||-
|-
|Cost
| ||-||+
|-
|Cost Tables (FSAE)
| ||-||+
|-
|Manufacturability
||-|| ||+
|-
|Pressure Capacity
||+*|| ||-
|-
|Reusability**
||-|| ||+
|-
|e85 Compatibility
||+|| ||-
|-
|colspan="4"|
<nowiki>*</nowiki>Depends on wall thickness, see table above

<nowiki>**</nowiki>New design or small adjustments that need to be made
|}

==Filling==
Fuel filling is critical to consider in the system design in three ways: safety, function, and rules compliance.
To ensure a safe filling procedure, common sense should be used to prevent fuel spillage and ease of access. An easy process is a safe one. A rules mandated splash guard can further protect the vehicle, driver, and fuel filling team-mate.
===Filler Neck===
The filler neck has a rules specified vertical height, maximum angle, and internal diameter. Meeting these requirements helps ensure the tank can be filled safely, easily, and will pass technical inspection. Because this is often overlooked in design, and creating a new fuel tank or modifying an existing one is quite difficult on the day of competition, it is recommended to strictly follow rules as written, and to ask rule questions if clarifications are needed.

It is unusual but not unprecedented for a technical inspector to measure the internal diameter of the fuel filler neck, or the vertical height if it is visually unclear. Often in these cases, a gas can of the type used by the fuel filling team at competition is used to ensure that the vehicle can be safely fueled even if the rules are not entirely met. If the rules breach is egregious, the car will likely not be allowed to pass tech even if it may be safely fueled.
===Sight Tube===
There are vertical height and routing requirements to the sight tube. A frequently discussed solution is a clear, fuel resistant plastic used as the filler neck material itself to comply with both filler neck and sight tube rules. The fuel filling team at US competitions ask the teams to not mark the fuel fill line themselves and will mark it themselves at the fuel fill station to avoid incorrectly marked fill levels causing an accident.

==Venting==
The fuel tank is required to be able to vent excess vapor pressure while the car is in the correct orientation, but not allow fuel leaking in the event of a vehicle rollover. A common solution is to purchase or create a custom vented fuel cap. Custom vented fuel caps may be subject to a water leak test during tech inspection.

==Pump and Pressures==
Fuel pressures can be divided into two categories for different applications. Most FSAE/FS teams run fuel pressures under 10 bar, which are classified as ''low pressure''. Low pressure fuel is sufficient for single or multipoint manifold injection. Some teams chasing performance or academic goals may opt for high pressure fuel injection to facilitate direct injection.

Pumps are usually specified to pressures greater than that used by the injectors. A fuel pressure regulator is used in-line to achieve final fuel pressure. Fuel pressure regulators can be blocking (returnless or non-return-style) or bypass (return-style). Returnless fuel injectors have only one input and and one output port allowing for a simpler routing system and thus reducing points of failure. These returnless fuel injectors do need a bypass valve at the pump to relieve pressure. The design of these regulators allows for pressure creep, is more sensitive to debris, and are not able to consistently/accurately read pressure without the engine running<ref>Fuller, David. Light, John. "Quick Tech: Return- vs. Non Return-Style Fuel Pressure Regulators for Low-Pressure Fuel Systems" ''On All Cylinders''. https://www.onallcylinders.com/2017/01/12/quick-tech-return-vs-non-return-style-fuel-pressure-regulators-low-pressure-fuel-systems/</ref>. Bypass regulators can be more expensive and drive more complex routing, but yield more accurate fuel readings, have a longer life, and are easier on the fuel pump.
===Low Pressure===
Low pressure is often the default injection pressure for FSAE as most motorcycle or snowmobile engines run at pressures around 3-3.5 bar <ref>Bacon. "Fuel Pressure Specs". ''600RR.NET'', Mar. 4, 2009. https://www.600rr.net/threads/fuel-pressure-specs.131524/</ref><ref>gixxerkart504. "Fuel Pressure???" ''GIXXER.COM/'', Sep. 22, 2008. https://www.gixxer.com/threads/fuel-pressure.199809/</ref><ref>
Be.St.MX. "2012 yzf 450 fuel pressure, fuel pump symptoms bike wont start". ''Thumper Talk'', Sep. 4, 2017. https://www.thumpertalk.com/forums/topic/1240219-2012-yzf-450-fuel-pressure-fuel-pump-symptoms-bike-wont-start/</ref>. Single point injection or throttle body injection (TBI) is when fuel is injected at the throttle, similar to a carburetor. Most modern fuel systems use multipoint injection or port injection (PI), placing the injectors after the plenum and as close as possible to the engine. This results in fuel being sprayed into the intake ports.
===High Pressure===
In order to run a direct injection setup, fuel pressures need to exceed 10 bar. These extreme pressures force higher safety requirements by rules. The major regulation in FSAE is that fuel lines must be stainless steel hard-line or "Aeroquip FC807 smooth bore PTFE hose with stainless steel reinforcement and visible Nomex tracer yarn". Teams can run something similar if the team gets approval before competition. Any fuel line before the boost pump is considered low pressure and is not subject to the fuel line restrictions.

The fuel rail and it's attachments must be able to withstand maximum force from the fuel line (not including cylinder pressure).


==Injectors==
===Placement===
The injector placement can be divided into two categories: manifold injection or direct injection. Manifold injection is easier to implement as the pressures are lower, rules are less strict, and it does not require modifications to most engines used in FSAE.
====Throttle Body Injection====
Throttle body injection (TBI) or single point manifold injection is the oldest electronically controlled fuel injection. It is analogous to a carburetor in concept but allows much more precise and tunable control. This is uncommon as it is older technology and has less benefits for efficiency than other approaches. Because the fuel is injected so high in the intake, a greater proportion of the fuel is lost to the walls of the manifold so control is less precise.
====Port Fuel Injection====
Fuel Injected into the [[Intake|ports]] or multipoint manifold injection just before entering the combustion chamber. The most common type of fuel injection in FSAE, port injection offers high levels of control at a lower cost than DI.


Injecting fuel into the port can be done when the intake valve is open or when the intake valve is closed. Injecting into the port when the valve is open is colloquially referred to as "poor man's direct injection". There are benefits and drawbacks to each.

====Direct Fuel Injection====


===Classification by Resistance===
====Low Resistance====
Usually 0.5 - 5 Ohm. Also called "peak-and-hold-injectors". From this name you can directly infer the mode of operation. In the beginning the ECU has to give a high current to the valve to open it quickly. This is the peak. Then a lower current is sufficient to keep the valve open. A common ratio of the currents is 4:1.

However, for this the ECU must also have a controller that can supply the different currents. The advantage of this system is that due to the high current at the beginning the valve can be opened very quickly. However, this is no longer necessary nowadays, because even valves with high resistance can provide the necessary flow.
====High Resistance====
Ususally 8 - 15 Ohm. Also known as a "saturated drive injector". These are much easier to control, as only the circuit has to be closed and the resistance of the valve controls the current.
==Critical Fasteners==
All fasteners on the fuel system are critical. Nylon locking fasteners are not appropriate near the engine such as the fuel rail. The nylon will soften and will not retain the nut. Most technical inspectors will not catch this but it's a pain to change and better to just do it right the first time.
=Fuel Strategy=
==How it's scored at comp==
[[File:ImpactofFuelUsageinCompetitionbyType.png|thumb|right|Points per L Fuel used in 2021 Michigan Competition]]
Since FSAE and FS considers how much fuel is used as well as how fast each car goes, the cost of fuel in terms of competition score must be considered. There are many ways to analyze the impact of the fuel usage on the competition score.

Unfortunately, there is no dial on the car that teams can turn to raise or lower their fuel consumption. Other factors that impact fuel use besides Efficiency Event scores are usually prioritized such as engine choice, torque, tuning, etc.

A simplistic, black box analysis using the 2021 Michigan Efficiency Event scores shows that gasoline is worth about 17 points per gallon used, and E85 is worth about 15 points per gallon used. The lap-time of the car has almost no correlation to the efficiency scores<ref>Scatter plot of lap time v efficiency score is easy enough to create. I may add one here if I have time.</ref>.
{{clear}}

==Fuel Choice==
One of the biggest choices fueling system design engineers must make is which fuel to run. Teams with limited resources may find that cost and/or convenience may outweigh all other design considerations. Proper documentation and explanation of these restrictions will prevent this concession to real world conditions from being counted against a team in the design event.

The team must decide whether or not to pursue running E85 before many other fuel system decisions. The octane rating of E85 lies around 100, but specific aspects of the fuel mean it is not a direct replacement. The largest difference is the specific energy. E85 has about 75% of the energy per unit mass that gasoline has<ref>https://dsportmag.com/the-tech/education/getting-tanked-the-e85-files-part-1/3/</ref> so the fuel tank will have to be bigger.

==Efficiency==
===Consumption vs. Thermal Efficiency===
===BSFC===
Brake specific fuel consumption is another way to view efficiency and is used to compare engine efficiency despite size differences<ref> The wikipedia page for BSFC is hilariously poorly written. It's inscrutable and incomplete but has this enormous table of various engine BSFC stats.</ref>. It measures how much fuel is used (in lbs/hr) divided by power (hp). It is usually used to show a map of engine operating points to visualize engine efficiency across load (usually BMEP) and RPM.

'''Calculation'''<ref>“Brake Specific Fuel Consumption (BSFC).” X-Engineer, https://x-engineer.org/automotive-engineering/internal-combustion-engines/performance/brake-specific-fuel-consumption-bsfc/</ref> copying from old school notes so i'll have to add context later -simon

this is for finding fuel consumption (mpg or equivalent) w bsfc chart
{| class="wikitable"
|Pme ||Mean Effective Pressure
|-
|nmot ||Motor speed
|-
|iG ||Gear Ratio (for selected gear)
|-
|isec ||FDR
|-
|rdyn ||Dynamic Radius of Tire
|-
|Vd ||Displacement Volume of Engine
|-
|i ||Constant
|-
|Freq ||Tractive force required
|}

<math> P_{me} = \frac{(2\pi*T_{motor,required})}{(V_d * i)} = \frac{(2\pi)}{(V_d*i)} * \frac{(F_{req} * r_{dyn})}{(i_G * i_{sec})} </math>

<math> n_{motor} = \frac{Velocity*i_G*i_{sec}}{2\pi*r_{dyn}} </math>

be (fuel consumption) usually experimentally determined

<math> B_{time} = \frac{b_e*P_{me}}{\rho_{fuel}} = \frac{b_e*P_{me}*V_d*n_{motor}*i}{\rho_{fuel}} </math>

<math> B_{distance} = \frac{B_{time}}{V} </math>

i = 0.5 for 4-stroke engine

=References=

Intake

2025-05-19T18:39:24Z

SpookySimon: /* Resonance Tuning */

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperically with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457. I have it on relatively good authority that the team that ran this setup also cheated the intake restrictor diameter by using a non-circular opening. Additionally my coworker who was on the team claimed they also ran a PCV line from the crank to the intake after the restrictor and vented the crank case to ambient so they were able to pull additional air through the crank case, unsure of the veracity of this claim.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.


=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Resonance Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}


A typical intake valve will open before TDC and close after BDC. When the piston travels down to begin the intake stroke, the pressure in the cylinder drops. This pressure differential draws air through the intake port from the runner, and plenum. The pressure at each of these points continues to drop as the piston continues to travel down. This develops a low pressure (rarefaction) wave which will travel back up the intake runner. Once the low pressure wave hits the change in volume of the plenum, it is reflected back down the intake runner as a positive pressure wave.

It is a common misconception among FSAE students and adults who work on engines that the pressure wave mechanism is due to the air "bouncing" off of the closed intake valve, this is incorrect. If that was true, the positive pressure wave generated by this will reflect back at the plenum interface as a negative pressure wave and cause a deleterious effect when "tuned".

The piston begins to travel up before the intake valve closes. This does increase pressure in the cylinder and runner which can cause reverse flow at very low engine speeds but is generally neglected. At medium to high engine speeds, the momentum of the air flow into the cylinder will continue to drive air into the cylinder even after BDC. This effect of momentum is known as the "ram effect".

Resonance tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.

=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Intake

2025-05-19T18:15:02Z

SpookySimon: /* Intake Tuning */

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperically with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457. I have it on relatively good authority that the team that ran this setup also cheated the intake restrictor diameter by using a non-circular opening. Additionally my coworker who was on the team claimed they also ran a PCV line from the crank to the intake after the restrictor and vented the crank case to ambient so they were able to pull additional air through the crank case, unsure of the veracity of this claim.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.


=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Resonance Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}


Resonance tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex ram tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.

=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Intake

2025-05-19T18:14:34Z

SpookySimon: /* Resonance Tuning */

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperically with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457. I have it on relatively good authority that the team that ran this setup also cheated the intake restrictor diameter by using a non-circular opening. Additionally my coworker who was on the team claimed they also ran a PCV line from the crank to the intake after the restrictor and vented the crank case to ambient so they were able to pull additional air through the crank case, unsure of the veracity of this claim.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.


=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold (ram tuning) and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Resonance Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}


Resonance tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex ram tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.
=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Intake

2025-05-19T18:13:29Z

SpookySimon: /* Resonance Tuning */ I'm pretty sure we made some critical errors writing this - I'm rereading heywood and it really doesnt reflect what we wrote here

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperically with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457. I have it on relatively good authority that the team that ran this setup also cheated the intake restrictor diameter by using a non-circular opening. Additionally my coworker who was on the team claimed they also ran a PCV line from the crank to the intake after the restrictor and vented the crank case to ambient so they were able to pull additional air through the crank case, unsure of the veracity of this claim.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.


=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold (ram tuning) and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Resonance Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}

Ram tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex ram tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.
=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Intake

2025-05-05T19:14:02Z

SpookySimon: 2002 cheating allegations by my coworker lmao

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperically with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457. I have it on relatively good authority that the team that ran this setup also cheated the intake restrictor diameter by using a non-circular opening. Additionally my coworker who was on the team claimed they also ran a PCV line from the crank to the intake after the restrictor and vented the crank case to ambient so they were able to pull additional air through the crank case, unsure of the veracity of this claim.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.


=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold (ram tuning) and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Ram Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}

Ram tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex ram tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.
=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Intake

2025-05-05T19:08:10Z

SpookySimon: /* Plenum */ imperially ->imperically

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperically with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.


=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold (ram tuning) and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Ram Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}

Ram tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex ram tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.
=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Intake

2025-05-05T19:07:14Z

SpookySimon: /* Material Choice */ addition of ultem which i've never seen before this year

The '''intake''' system has a dominant effect on the torque curve and behavior of the powertrain system. All air used by the [[engine]](s) for combustion must pass through a 20 mm or 19 mm opening for gasoline or E85 fueled vehicles respectively, commonly referred to as a [[Restrictor|restrictor]]. The restrictor limits the theoretical power limit of the engine.
=Intake Design=

==Structure==
[[File:NAIntakeDiagram.png|right|middle|thumb|Diagram of NA Intake System]]Following the path the air follows as it enters the engine, the naturally aspirated intake system is made of the following components: the air filter, the throttle body, the restrictor, the plenum, the manifold, and the engine mounting. The air filter's sole responsibility is to stop water or particulates from entering the engine, these could cause engine damage or even failure. The throttle body allows for driver modulation of mass air flow into the engine, there-by controlling engine torque and speed. The plenum acts as a capacitor to smooth air flow into the cylinders and can be tuned to increase volumetric efficiency. The manifold consists of runners that channel air from the plenum into each cylinder. {{Clear}}[[File:MiscIntake.JPG|left|middle|thumb|Forced Induction Intake System Diagram]]
In forced induction applications, allowing a manifold between the restrictor and throttle body will limit the effects of the restriction. This is negated in FSAE by preventing a large volume (plenum/manifold, intercooler, etc.) prior to the throttle body (Rule IC.2.5.3). The order of system components defined by rules can be seen in the figure right and each component is discussed further down this page.{{Clear}}
==Packaging==
[[File:Intake and fuel packaging.PNG|right|middle|thumb|I.C.1.2 Packaging Restrictions]]
Packaging of the intake manifold has minor if any impact on the performance of the engine, but it can impact the aerodynamics of the car, particularly the rear wing (if the car has one). All intake packaging schemes can be categorized into the following: A top feed (or center feed), Side feed, and bottom feed. Although not true for every team, the choice is often based on manufacturing, serviceability and similar non-performance goals. Certain form factors lend themselves to intake manifold styles and vice-versa. Conical spline intakes are almost always found in a center feed configuration. Log style intake manifolds when used in a side feed configuration can be packaged very tight.
<gallery>
Side Feed.png|Side Feed
File:Top-Center Feed.png|Top-Center Feed
File:Conical Spline.png|Conical Spline
</gallery>
{{clear}}

==Material Choice==
The material used for the intake has a much lower impact on the performance than other tuning variables but warrants consideration. The major driving factors to consider are feasibility related: whether it is cost-effective, feasible to create the design the team has made, reliable enough to last through testing and competition, and similar. There are of course differences in the materials chosen that will be discussed here, but is important to understand the material choice is not expected to make a significant difference in dynamic event performance.

Common materials used by teams are below 
''Please add to this list if your team uses a material not mentioned here''
{| class="wikitable"
|-
!|Type
!|Material
!|Construstion
!|Notes
|-
| rowspan="1"|Metals


|[[Aluminum]]
|Welded sheet and tubing
|May exchange heat with ambient air if not coated
|-
| rowspan="4"|Plastic


|Nylon
|Usually 3D printed
|Nylon is one of the few 3D printable plastics that is gasoline resistant
|-
|Nylon - Carbon or Glass Fiber Reinforced
|Usually 3D printed
|Often outsourced, many institutions do not have in house capabilities to print this or won't want to
|-
|Ultem/PEI
|3D Printed
|
|-
|Other
|Off the shelf injection molded
|Available 3rd party solutions
|-
| rowspan="2"|Composite


|Carbon Fiber
|Vacuum bagged, Infusion, Prepreg
|
|-
|Fiberglass
|Vacuum bagged, Infusion
|Not as common as carbon fiber
|}

==Plenum==
Because the engine takes in air in only one part of the combustion cycle, the airflow out of the intake system is inherently pulsed. The pulsing allows less mass airflow into the system than a smooth airflow would (for many reasons, the most basic of which being that the low pressure waves reduce the airflow more than the high pressure waves increase it).

One useful analogy is comparing the system to a circuit where the output current is pulsed. The restrictor acts as a resistor (hopefully obvious). A basic way to smooth out the circuit is to add a capacitor. In the real world, we do this by adding a volume of air after the restrictor known as a plenum.

The plenum in series with the restrictor creates a pseudo low pass filter that will help smooth out the pulsed air flow characteristics of the intake. Since the restrictor is a fixed size, the "circuit" is tuned by changing the capacity (capacitance hint hint) of the plenum. If the plenum is too small, the non-uniform nature of the intake will significantly decrease power output. If the plenum is too large, the throttle will no longer be able to predictably control the air flow.

The size of the plenum is tuned imperially with many FSAE papers available for comparison. The shape of the plenum can be assumed to be negligible, the dominant characteristics of the plenum shape will likely be your discharge/flow coefficients at the interface to the restrictor and runners.


The phrase dual plenum can refer to two different designs, two plenum volumes in parallel (often called dual plane) or two in series. Lawrence Technical ran a two in parallel plenum design, tying a pair of cylinders to each plenum<ref>Jawad, Badih A., et al. “Formula SAE Dual Plenum Induction System Design.” SAE Technical Paper Series, 2002, https://doi.org/10.4271/2002-01-0457.</ref>. Series plenums are used to equalize airflow to the cylinders on intakes where the runners are not equidistant to the throttle body. These are most common on side intake log-style manifolds<ref>Bufkin, James. “Study of Intake Manifolds Used by Audi Sport for the Inline 5.” Bufkin Engineering, Inc., 29 Nov. 2004, https://www.bufkinengineering.com/intake%20manifolds.htm.</ref>.

=Intake Tuning=

Tuning the intake is either modifying the system's response to different engine speeds, reducing pressure losses the air has to overcome, or adjusting the turbulence of the flow to aid in charge mixing. The most common and impactful form of tuning is changing the response to different engine speeds, or the engine's frequency response. This takes two forms: the first is in modifying the length of the manifold (ram tuning) and the second is in modifying the shape of the manifold.(including Helmholtz resonators).

The basic principle behind frequency focused tuning strategies is that a cylinder draws air differently during different parts of the four stroke cycle. Ostensibly, a cylinder only takes in air for a quarter of a four stroke cycle, meaning that there is a stop-starting of the flow of air into the cylinder. This occurs at a frequency dependent on the rpm of the engine, hence this form of tuning is done to optimize performance at a selected rpm range.

The torque curve can be viewed as a frequency response curve.
==Ram Tuning==
{{#evt:service=youtube|id=https://www.youtube.com/watch?v=-l7o64Tc5hk|alignment=right}}

Ram tuning is implemented by modifying the length of the manifold such that the pressure wave formed on each cycle travels along the manifold and is reflected back, arriving just as the cylinder completes the cycle and takes in its next charge. When done correctly, the pressure at at the intake port will be higher during the intake stroke, giving better volumetric efficiency for the engine. The parameters to adjust are the length of your intake runners and their diameter. Intake runner length is often the easiest parameter to tune and often has the biggest impact on the system. A longer runner will resonate at a lower frequency. A larger diameter intake runner will lower the speed of the air, raising the resonant frequency for a fixed length (someone check me on this).

In more complex ram tuning applications, actuated baffles can be created to vary engine torque curve. This is done on many production cars to allow different behavior at low and high RPM.
===Trade-Offs===
The fundamental tradeoff with most intake tuning is to prioritize a higher peak torque or a wider, flatter torque curve.
====Pros====

* All intake systems have this frequency response, so you do not need extra features to enable tuning
* Relatively simple system
* Allows for movement of your torque curve

====Cons====

* Simulations are often inaccurate and may require on vehicle testing to confirm optimal performance
* Can only tune to one optimal frequency, unless baffles are integrated

==Helmholtz Resonators==
Helmholtz resonators work by having a thin neck followed by an open cavity attached to the engine's intake. Their design result in low pressure at the neck, sucking in more air, and resulting in higher pressure air in the cavity, which can then feed the engine. They can be thought of as tuned mass dampers (and can be modeled as such). Helmholtz resonators are most effective in single cylinder systems, as the flow through the intake can be dominated by pulsed flow characteristics at high rpms [citation definitely needed]. These are most often seen in exhaust systems to control the sound output.
===Trade-Offs===
====Pros====
Helmholtz tuning can be used to suppress an unwanted torque spike somewhere in the curve.
====Cons====
Helmholtz tuning is very hard to predict, and requires a complex additional feature that may be difficult to package and have an unpredictable or negligible effect on performance.
=Throttle Control=
{{Main|Throttle}}The throttle allows modulation of the air coming into your intake system. Within FSAE, the throttle must fall between your restrictor and manifold or, in boosted applications, between the turbocharger/supercharger and manifold. Throttle designs include actuation by throttle cable or by electronic throttle body (ETC or drive-by-wire).
=Restrictor=
{{Main|Restrictor}}According to IC.2.4.1, the competition requires all air entering the engine to first pass through a 20mm diameter hole when using gasoline or a 19mm hole when using e85. This restrictor places a theoretical upper limit on the power that can be generated by a naturally aspirated engine. This is checked in competition by removing the [[Throttle|throttle body]] and inserting a test instrument of the appropriate size in a go-no-go test.
=Forced Induction=
Forced induction is done by utilizing a compressor to increase the pressure seen in your manifold/plenum, leading to increased engine power and efficiency. This is accomplished by the higher manifold pressures being able to force more air into the cylinder/s on each intake stroke. The increased air in the cylinder means you can burn more fuel and maintain the same air-fuel-ratio. A denser charge will also combust faster, yielding greater energy utilization and efficiency. Common methods of implementing forced induction is by turbocharging, supercharging, or procharging. Within FSAE, a fair number of teams run forced induction, but the majority remain naturally aspirated. <ref> At the 2018 FSAE Michigan competition 9 teams out of 120 (?) openly used forced induction: UMich (CBR), Cornell (CBR), Wisconsin (YZ450), Kettering (WR450), Rose (YZ450), UNC Charlotte (510cc single, KTM?), Minnesota Mankato (YZ450), UNH (KTM 450), Quebec-Chicoutimi (Genesis 80fi), Mississippi (CBR)</ref>
==Turbocharging==
===Theory===
[[File:Turbo Diagram.gif|right|middle|thumb|Turbo system diagram]]A turbocharger works by compressing intake air by harvesting waste enthalpy, traditionally discarded, from the exhaust. The general flow of air through a turbocharged system can be seen to the right. Theoretically, the higher plenum pressure you can run, the more power you can extract from your engine package. One limiting factor is self-detonation of the charge or knock. The liability to knock is based upon many factors, including but not limited to, fuel choice, fuel injection location, and compression ratio.
=====Cooling Charge Air=====
The charge air cooler, also known as an intercooler, is designed to lower your charge air temperature. The intake air temperature increases due to compression, according to the [https://www.grc.nasa.gov/WWW/K-12/airplane/compth.html equation] for compressor pressure ratio.
:(P2/P1) = (T2/T1)γ/(γ-1)

Gamma is 1.4 for dry air. This equation must be used with absolute pressure and temperature. ''P2/P1'' is also known as pressure ratio. For example, a pressure ratio of two (1 atm to 2 atm) will lead to a 20% increase in intake air temperature. This means for an inlet temperature of 20C, your plenum temperature will be approximately 85C. If you run low boost, the need for an intercooler may be able to be avoided. Alternatively, injecting E85 upstream of the runner to cool the air via the evaporation may be feasible. This is only done due to the high latent heat of evaporation and low evaporation temperature for E85. This method is beneficial as it provides cooling and well mixed air fuel mixture. However, this method requires an extremely careful tune otherwise your plenum is liable to turn into shrapnel.

====Blow Off Valve====
The purpose of a blow off valve (BOV) is to control your plenum/manifold pressure and prevent compressor surge by dumping excess flow. This works in conjunction with a wastegate to manage plenum pressure to your desired pressure.
===Trade-Offs===
==Supercharging/Procharging==
ETS pls
===Theory===
===Trade-Offs===
==Forced Induction Manifold Designs==
For Turbos:

Connecting the intake and exhaust manifolds
* Over the top
* Around the side
* I dont think anyones gone under the engine but im not willing to put money on it
avoid heating intake with exhaust headers

intercooler placement, mounting, (maybe do this in the cooling section?)
=References=
[[Category: Internal Combustion]]

Safety Wire

2024-12-10T20:17:03Z

SpookySimon: comma

[[File:Safetywire.jpg|right|middle|thumb|Examples of Safety Wiring]]
'''Safety wire''' is as a positive retention strategy for [[Threaded_Fasteners|bolts]] in blind holes. The thin [[Steel|steel]] wire stops the rotation of the bolt by threading through holes in the bolt-heads. After threading the wire through the bolt-head, twisting the wire tightens it and keeps it in place. Routing the wire around the head of the bolt in the direction of tightening (clockwise, or in a 'Z' shape, for a right hand threaded bolt) keeps the wire under tension throughout vehicle operation. If it is routed in the wrong direction, the wire will lose tension and be unable to retain the fastener.

On occasion, safety wire can be used in conjunction with other positive locking mechanisms, but it is not advised to safety-wire a bolt that is retained by a nut, as the wire may stop the bolt from moving while allowing the nut to move, facilitating failure.

In technical inspection, safety wire is judged differently by each inspector. A general rule of thumb is that it should be tight and look like a 'z'. If it looks like an 's', it is wound incorrectly for a right-hand threaded bolt. Technical inspectors generally will pass minor errors, such as untucked ends, overtightened or under-tightened twists, incorrect twist direction, etc.
[[Category:Fasteners]]

Safety Wire

2024-12-10T20:16:48Z

SpookySimon: clarifying "typically" to mean rh threaded bolt

[[File:Safetywire.jpg|right|middle|thumb|Examples of Safety Wiring]]
'''Safety wire''' is as a positive retention strategy for [[Threaded_Fasteners|bolts]] in blind holes. The thin [[Steel|steel]] wire stops the rotation of the bolt by threading through holes in the bolt-heads. After threading the wire through the bolt-head, twisting the wire tightens it and keeps it in place. Routing the wire around the head of the bolt in the direction of tightening (clockwise, or in a 'Z' shape for a right hand threaded bolt) keeps the wire under tension throughout vehicle operation. If it is routed in the wrong direction, the wire will lose tension and be unable to retain the fastener.

On occasion, safety wire can be used in conjunction with other positive locking mechanisms, but it is not advised to safety-wire a bolt that is retained by a nut, as the wire may stop the bolt from moving while allowing the nut to move, facilitating failure.

In technical inspection, safety wire is judged differently by each inspector. A general rule of thumb is that it should be tight and look like a 'z'. If it looks like an 's', it is wound incorrectly for a right-hand threaded bolt. Technical inspectors generally will pass minor errors, such as untucked ends, overtightened or under-tightened twists, incorrect twist direction, etc.
[[Category:Fasteners]]

FMEA

2024-04-26T16:41:40Z

SpookySimon: adding fsae ev fmea link

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).

An FMEA is required in FSAE for certain parts of an EV car. The competition puts together a somewhat comprehensive presentation on completing the competition's required document submission here:
* https://www.fsaeonline.com/cdsweb/gen/DownloadDocument.aspx?DocumentID=8d20f722-97c3-4a9f-9344-6baed6cc332e

=Basics=
==Analytical Lens==
At a lay level, a FMEA should be a list of different ways things can go wrong, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break? (Failure Mode)
* What will happen to the car if this thing goes wrong? (Failure Effect(s))
* How likely is this thing to go wrong?
* What can we do to stop this from happening?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* How could we detect a failure has occurred?
* How could we detect a failure will occur?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?
* If this failed, would the car continue to be rules compliant?
* If this failed, could the driver be in danger?
* If this failed, could a bystander or track volunteer be in danger?
* How quickly can this be repaired if it failed?
* Would a new component have to be bought/machined or is this meant to be repairable?
* How long is the lead time for a replacement component?

==Analytical Techniques==
FMEA is a fundamentally qualitative effort to manage risk. There are many ways to put numbers to different facets of the process, but frequently "fuzzy" approaches are used where there is no way to quantify unknowns.

=When to use FMEA=
==Design Phase==
The strength of FMEA is greatest when utilized during the design phase of a build. Early in the design, it is possible to determine critical failure outcomes, risk levels, and experience or research can aid in determining failure points. As the design matures, component specs, features and integration requirements should be carefully investigated to pre-empt possible failure modes. This includes but is not limited to stress concentrators, build tolerance and tolerance stack-ups, material fatigue, wear-in, wear-out, driver error, competition volunteer error, load paths, road load, team-members being lazy or ignorant, poke-yoke, torque specs, fretting, dirt and grime, contamination, corrosion, water ingress, extreme cold or extreme heat etc.
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

Center of Gravity

2024-04-26T16:30:59Z

SpookySimon: /* Measure the CG */ subscipting the b wo it doesnt look like w*b

The '''center of gravity''' (also referred to as '''center of mass''' or '''CG''') is the average location of the weight of the car. The point in space that sums the vehicles [[Mass|mass]] in a single point. To put it in simple to visualize terms, if we could suspend the car from that point only we would not witness any forces twisting the car into a specific orientation since the mass would be equally distributed in all three dimensions. 
==Measure the CG==
===Total Vehicle CG===
Measuring the total planar center of gravity is fairly easy with only 4 weight scales, one under each [[Tires|tyre]]. We say total because we are not making a distinction between non-suspended and suspended mass. Make sure floor is level so that the weight on the scales doesn't get influenced by inclination.

We can start by determining the distance of the CG to the front axle. This is also normally referred to as the distance "'''a'''".

<math>a = \frac{ W_{rear} }{ W_{total} } W_b</math>

Where <math>Wb</math> corresponds to the wheelbase of the car (distance between axles), <math>W_{rear}</math> the rear weight (sum of both rear tyre scales) and <math>W_{front}</math>the front weight (sum of both front tyre scales). From this we can get the distance normally referred as "'''b'''"(from rear axle to CG) just by subtracting from the wheelbase:

<math>b = \frac{ W_{front} }{ W_{total} } W_b = W_b - a</math>

You can also apply the same formulas to find lateral location of the center of gravity. For a balanced and best performing car all around it should be in the center longitudinal line of the car but it should be measured to find if this is true for a specific car. We can call this measurement of distance of CG to the side as "'''c'''" for example and calculate it as such:

<math>c = \frac{ W_{left} }{ W_{total} } Track</math>

Once again the advised it for "'''c'''" to be half the track of the car. For cars with different front and rear tracks you can still calculate this "'''c'''".

Now for determining the '''height of the center of gravity''' we need to tilt the car around one of the horizontal axis. This could be with a tilt table or just by raising both the front or the rear wheels (as illustrated on Figure 1).[[File:Image010.jpg|link=http://www.thecartech.com/subjects/auto_eng/Center_of_Gravity.htm|right|middle|thumb|Figure 1 - Measuring height of the CG]]

[under construction - Formula missing]

==Optimum Center of Gravity==
==Mass Centroid Axis==
[[File:Masscentroid.jpg|right|middle|thumb|The Mass Centroid Axis]]
The Mass Centroid axis is measured in sections of the car, it's the axis, which isn't necessarily linear, which goes through every 2-d center-of-gravity. It doesn't have to be measured at every point in the car, you can approximate and get a better sense of the roll center moments, which aren't just measured on a parallel c.o.g. axis to the ground.
[[Category:Vehicle Dynamics]]

Center of Gravity

2024-04-26T16:29:44Z

SpookySimon: /* Measure the CG */ cleaning up

The '''center of gravity''' (also referred to as '''center of mass''' or '''CG''') is the average location of the weight of the car. The point in space that sums the vehicles [[Mass|mass]] in a single point. To put it in simple to visualize terms, if we could suspend the car from that point only we would not witness any forces twisting the car into a specific orientation since the mass would be equally distributed in all three dimensions. 
==Measure the CG==
===Total Vehicle CG===
Measuring the total planar center of gravity is fairly easy with only 4 weight scales, one under each [[Tires|tyre]]. We say total because we are not making a distinction between non-suspended and suspended mass. Make sure floor is level so that the weight on the scales doesn't get influenced by inclination.

We can start by determining the distance of the CG to the front axle. This is also normally referred to as the distance "'''a'''".

<math>a = \frac{ W_{rear} }{ W_{total} } Wb</math>

Where <math>Wb</math> corresponds to the wheelbase of the car (distance between axles), <math>W_{rear}</math> the rear weight (sum of both rear tyre scales) and <math>W_{front}</math>the front weight (sum of both front tyre scales). From this we can get the distance normally referred as "'''b'''"(from rear axle to CG) just by subtracting from the wheelbase:

<math>b = \frac{ W_{front} }{ W_{total} } Wb = Wb - a</math>

You can also apply the same formulas to find lateral location of the center of gravity. For a balanced and best performing car all around it should be in the center longitudinal line of the car but it should be measured to find if this is true for a specific car. We can call this measurement of distance of CG to the side as "'''c'''" for example and calculate it as such:

<math>c = \frac{ W_{left} }{ W_{total} } Track</math>

Once again the advised it for "'''c'''" to be half the track of the car. For cars with different front and rear tracks you can still calculate this "'''c'''".

Now for determining the '''height of the center of gravity''' we need to tilt the car around one of the horizontal axis. This could be with a tilt table or just by raising both the front or the rear wheels (as illustrated on Figure 1).[[File:Image010.jpg|link=http://www.thecartech.com/subjects/auto_eng/Center_of_Gravity.htm|right|middle|thumb|Figure 1 - Measuring height of the CG]]

[under construction - Formula missing]

==Optimum Center of Gravity==
==Mass Centroid Axis==
[[File:Masscentroid.jpg|right|middle|thumb|The Mass Centroid Axis]]
The Mass Centroid axis is measured in sections of the car, it's the axis, which isn't necessarily linear, which goes through every 2-d center-of-gravity. It doesn't have to be measured at every point in the car, you can approximate and get a better sense of the roll center moments, which aren't just measured on a parallel c.o.g. axis to the ground.
[[Category:Vehicle Dynamics]]

Center of Gravity

2024-04-26T16:28:46Z

SpookySimon: /* Total Vehicle CG */ cleaning this bad boy up

The '''center of gravity''' (also referred to as '''center of mass''' or '''CG''') is the average location of the weight of the car. The point in space that sums the vehicles [[Mass|mass]] in a single point. To put it in simple to visualize terms, if we could suspend the car from that point only we would not witness any forces twisting the car into a specific orientation since the mass would be equally distributed in all three dimensions. 
==Measure the CG==
===Total Vehicle CG===
Measuring the total planar center of gravity is fairly easy with only 4 weight scales, one under each [[Tires|tyre]]. We say total because we are not making a distinction between non-suspended and suspended mass. Make sure floor is level so that the weight on the scales doesn't get influenced by inclination.

We can start by determining the distance of the CG to the front axle. This is also normally referred to as the distance "'''a'''". <math>a = \frac{ W_{rear} }{ W_{total} } Wb</math>

Where <math>Wb</math> corresponds to the wheelbase of the car (distance between axles), <math>W_{rear}</math> the rear weight (sum of both rear tyre scales) and <math>W_{front}</math>the front weight (sum of both front tyre scales). From this we can get the distance normally referred as '''"b"'''(from rear axle to CG) just by subtracting from the wheelbase:

<math>b = \frac{ W_{front} }{ W_{total} } Wb = Wb - a</math>

You can also apply the same formulas to find lateral location of the center of gravity. For a balanced and best performing car all around it should be in the center longitudinal line of the car but it should be measured to find if this is true for a specific car. We can call this measurement of distance of CG to the side as "'''c'''" for example and calculate it as such:

<math>c = \frac{ W_{left} }{ W_{total} } Track</math>

Once again the advised it for "'''c'''" to be half the track of the car. For cars with different front and rear tracks you can still calculate this "'''c'''".

Now for determining the '''height of the center of gravity''' we need to tilt the car around one of the horizontal axis. This could be with a tilt table or just by raising both the front or the rear wheels (as illustrated on Figure 1).[[File:Image010.jpg|link=http://www.thecartech.com/subjects/auto_eng/Center_of_Gravity.htm|right|middle|thumb|Figure 1 - Measuring height of the CG]]

[under construction - Formula missing]

==Optimum Center of Gravity==
==Mass Centroid Axis==
[[File:Masscentroid.jpg|right|middle|thumb|The Mass Centroid Axis]]
The Mass Centroid axis is measured in sections of the car, it's the axis, which isn't necessarily linear, which goes through every 2-d center-of-gravity. It doesn't have to be measured at every point in the car, you can approximate and get a better sense of the roll center moments, which aren't just measured on a parallel c.o.g. axis to the ground.
[[Category:Vehicle Dynamics]]

FMEA

2024-04-26T16:23:29Z

SpookySimon: /* Analytical Lense */

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
==Analytical Lens==
At a lay level, a FMEA should be a list of different ways things can go wrong, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break? (Failure Mode)
* What will happen to the car if this thing goes wrong? (Failure Effect(s))
* How likely is this thing to go wrong?
* What can we do to stop this from happening?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* How could we detect a failure has occurred?
* How could we detect a failure will occur?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?
* If this failed, would the car continue to be rules compliant?
* If this failed, could the driver be in danger?
* If this failed, could a bystander or track volunteer be in danger?
* How quickly can this be repaired if it failed?
* Would a new component have to be bought/machined or is this meant to be repairable?
* How long is the lead time for a replacement component?

==Analytical Techniques==
FMEA is a fundamentally qualitative effort to manage risk. There are many ways to put numbers to different facets of the process, but frequently "fuzzy" approaches are used where there is no way to quantify unknowns.

=When to use FMEA=
==Design Phase==
The strength of FMEA is greatest when utilized during the design phase of a build. Early in the design, it is possible to determine critical failure outcomes, risk levels, and experience or research can aid in determining failure points. As the design matures, component specs, features and integration requirements should be carefully investigated to pre-empt possible failure modes. This includes but is not limited to stress concentrators, build tolerance and tolerance stack-ups, material fatigue, wear-in, wear-out, driver error, competition volunteer error, load paths, road load, team-members being lazy or ignorant, poke-yoke, torque specs, fretting, dirt and grime, contamination, corrosion, water ingress, extreme cold or extreme heat etc.
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T16:23:16Z

SpookySimon: /* Basics */ techniques

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
==Analytical Lense==
At a lay level, a FMEA should be a list of different ways things can go wrong, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break? (Failure Mode)
* What will happen to the car if this thing goes wrong? (Failure Effect(s))
* How likely is this thing to go wrong?
* What can we do to stop this from happening?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* How could we detect a failure has occurred?
* How could we detect a failure will occur?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?
* If this failed, would the car continue to be rules compliant?
* If this failed, could the driver be in danger?
* If this failed, could a bystander or track volunteer be in danger?
* How quickly can this be repaired if it failed?
* Would a new component have to be bought/machined or is this meant to be repairable?
* How long is the lead time for a replacement component?

==Analytical Techniques==
FMEA is a fundamentally qualitative effort to manage risk. There are many ways to put numbers to different facets of the process, but frequently "fuzzy" approaches are used where there is no way to quantify unknowns.

=When to use FMEA=
==Design Phase==
The strength of FMEA is greatest when utilized during the design phase of a build. Early in the design, it is possible to determine critical failure outcomes, risk levels, and experience or research can aid in determining failure points. As the design matures, component specs, features and integration requirements should be carefully investigated to pre-empt possible failure modes. This includes but is not limited to stress concentrators, build tolerance and tolerance stack-ups, material fatigue, wear-in, wear-out, driver error, competition volunteer error, load paths, road load, team-members being lazy or ignorant, poke-yoke, torque specs, fretting, dirt and grime, contamination, corrosion, water ingress, extreme cold or extreme heat etc.
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T16:17:58Z

SpookySimon: /* When to use FMEA */ how fmea helps in design some things to look out for

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
==Analysis==
At a lay level, a FMEA should be a list of different ways things can go wrong, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break? (Failure Mode)
* What will happen to the car if this thing goes wrong? (Failure Effect(s))
* How likely is this thing to go wrong?
* What can we do to stop this from happening?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?
* If this failed, would the car continue to be rules compliant?
* If this failed, could the driver be in danger?
* If this failed, could a bystander or track volunteer be in danger?
* How quickly can this be repaired if it failed?
* Would a new component have to be bought/machined or is this meant to be repairable?
* How long is the lead time for a replacement component?

=When to use FMEA=
==Design Phase==
The strength of FMEA is greatest when utilized during the design phase of a build. Early in the design, it is possible to determine critical failure outcomes, risk levels, and experience or research can aid in determining failure points. As the design matures, component specs, features and integration requirements should be carefully investigated to pre-empt possible failure modes. This includes but is not limited to stress concentrators, build tolerance and tolerance stack-ups, material fatigue, wear-in, wear-out, driver error, competition volunteer error, load paths, road load, team-members being lazy or ignorant, poke-yoke, torque specs, fretting, dirt and grime, contamination, corrosion, water ingress, extreme cold or extreme heat etc.
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T16:11:18Z

SpookySimon: /* Basics */

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
==Analysis==
At a lay level, a FMEA should be a list of different ways things can go wrong, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break? (Failure Mode)
* What will happen to the car if this thing goes wrong? (Failure Effect(s))
* How likely is this thing to go wrong?
* What can we do to stop this from happening?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?
* If this failed, would the car continue to be rules compliant?
* If this failed, could the driver be in danger?
* If this failed, could a bystander or track volunteer be in danger?
* How quickly can this be repaired if it failed?
* Would a new component have to be bought/machined or is this meant to be repairable?
* How long is the lead time for a replacement component?

=When to use FMEA=
==Design Phase==
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T16:07:21Z

SpookySimon: /* Basics */

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
At a lay level, a FMEA should be a list of what-ifs, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break?
* What will happen to the car if this thing goes wrong?
* How likely is this thing to go wrong?
* What can we do to stop this from happening?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?
* If this failed, would the car continue to be rules compliant?
* If this failed, could the driver be in danger?
* If this failed, could a bystander or track volunteer be in danger?
* How quickly can this be repaired if it failed?
* Would a new component have to be bought/machined or is this meant to be repairable?
* How long is the lead time for a replacement component?

=When to use FMEA=
==Design Phase==
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T16:02:52Z

SpookySimon: /* Basics */

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
At a lay level, a FMEA should be a list of what-ifs, as in: "what if this part broke?". Each "what-if" being looked at in multiple ways:
* How could this part break?
* What will happen to the car if this thing goes wrong?
* How likely is this thing to go wrong?
* What can we do to stop this?

Additional detail can be included at whatever level of depth is deemed appropriate. Some further questions to ask include:
* What could cause this failure?
* What physically happens to the parts that are directly connected?
* What happens to the functionality of the system that this is a part of?
* To what extent is the functionality of the car effected?

=When to use FMEA=
==Design Phase==
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T15:52:01Z

SpookySimon: /* Basics */

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
At a lay level, a FMEA should be a list of what-ifs, each "what-if" being looked at in multiple ways:
* What will happen to the car if this thing goes wrong?
* How likely is this thing to go wrong?
* What can we do to stop this?

=When to use FMEA=
==Design Phase==
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T15:47:12Z

SpookySimon: intro

Failure Mode and Effect Analysis or FMEA is a structured method to analyze component and system reliability. It is a framework to look at how something fails (failure mode) and what happens when it does (failure effect).
=Basics=
=When to use FMEA=
==Design Phase==
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T15:44:55Z

SpookySimon: restructuring Page to make it fit with other pages

FMEA is a structured method to analyze component and system reliability.
=Basics=
=When to use FMEA=
==Design Phase==
==Manufacturing Phase==
==Testing Phase==
==Planning Phase==

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

FMEA

2024-04-26T15:44:06Z

SpookySimon: /* What is FMEA? */ real short blurb

=What is FMEA?=
FMEA is a structured method to analyze component and system reliability.
==Basics==
==When to use FMEA==
===Design Phase===
===Manufacturing Phase===
===Testing Phase===
===Planning Phase===

=Types of FMEA=
==System/Functional FMEA==
==Process FMEA==
==Design FMEA==
==Manufacturing FMEA==
==Software FMEA==
=How to Make an FMEA=
[[Category:Engineering Materials]]

Suspension Forces

2024-04-09T15:40:02Z

SpookySimon: /* Inboard vs outboard drive/brake */ subscript

==Forces in 6 Suspension Tubes Per Corner==
In double wishbone suspension systems typically seen on FSAE cars, there are 6 tubes connecting the wheel assembly to the vehicle:
# Upper Wishbone, Fore
# Upper Wishbone, Aft
# Lower Wishbone, Fore
# Lower Wishbone, Aft
# Push/Pull Rod or Spring/Damper (direct suspension)
# Toe Rod or Steering Tie Rod

==Applications==

* Proper design and selection of suspension tubes
* Proper design of upright / knuckle
* Better understanding of forces during different loadcases
* Proper design of bellcrank
* Proper design of mounting brackets of suspension tubes onto chassis
* Reduce failures, while keeping weight low
* Compliance analysis

==Analysis of Only the Push/Pull Rod (Incorrect Method)==
Some teams have assumed that the vertical force of the tire at the contact patch is exactly equal to the vertical component of the push/pull rod force, and used the component forces / similar triangles / Trigonometry method to calculate the force in the push/pull rod, ignoring the additional forces of the other 5 suspension tubes. '''This is incorrect''', and can underestimate forces by a factor of 2 or more. The method is most inaccurate on pull-rod suspension. Here, the upper wishbone applies an additional vertical force to the wheel assembly, which increases the loads on the pull-rod. [[File:Pullrod Forces2.png|right|middle|thumb|Upper Wishbone Increasing Forces on Pull-rod]]

==Static Free Body Diagram 6x6 Matrix Method==
Numerous papers on this method exist. A google search for "Formula SAE Suspension Forces Matrix" shows a couple, or check the [[Suspension Forces#See Also|See Also]] Section. The rest of this section provides only a summary with a few pictures. The video provides a detailed explanation in a very easy to understand format.

A ready-to-fill-in excel file, which accompanies the video is available at [https://github.com/fsaeillumina/suspension-forces https://github.com/fsaeillumina/suspension-forces] {{#ev:youtube|https://youtu.be/rhqZQ9Lic2o|600|center|Formula SAE Suspension Forces Matrix Video|frame}}
===Assumptions===
Because all of these have spherical bearings on both ends, they are two-force-members, so they will only see tension/compression forces. If the push/pull rod is mounted to a control arm, then it will introduce bending forces in that control arm. In order to calculate the axial forces in all 6 tubes, it will be assumed that they are all two-force members.

Acceleration of the wheel assembly is ignored here for simplicity.

===Inboard vs outboard drive/brake===
The forces through the suspension members also depend on the brake/drive setup. It is crucial to consider this in the calculation to properly represent the load paths.

For an inboard drive/brake, the driveshaft helps and reacts the moment that originates from the contact patch as the driveshaft itself is being stressed. For outboard drive/brake, the driveshaft is not stressed, and cannot transmit the torque like in the inboard scenario. Therefore, with an inboard layout, the driveshaft acts like a 7th link and typically reduces the loads going through the other suspension links. This can be compensated for in the calculation by the additional moment, My, when analysing inboard drive/brakes.

===Theory===
Apply sum of forces equals zero (Fx, Fy, and Fz are 3 equations), and sum of moments (torques) equals zero (Mx, My, and Mz are 3 equations) to the wheel assembly. Break up all 6 suspension tube force vectors into their x, y, and z components multiplied by the unknown magnitude of the force in each arm. The 6 equations and 6 unknowns form a solvable 6x6 linear system. [[File:Free Body Diagram.png|right|middle|thumb|Free Body Diagram Showing 3 of 6 Suspension Arms]]

===Solving===
A summary of the solution is given here. It is a decently long process. It is recommended the reader follow through a paper, or watch a video.

First determine the x, y, z components of each of the 6 tubes. In vector form, this is the same as the unit vectors of each tube, multiplied by the magnitude of the force of each arm. The latter of which will be left as a variable because it is unknown. [[File:Suspension Forces 1.png|right|middle|thumb|Breaking up Force Vectors into x, y, z components]]
[[File:Equations With Highlights.png|right|middle|thumb|Force Equations with Unit Vectors Highlighted in Red and Unknowns Highlighted in Orange]]

Calculating the moments from each tube is best done in vector form as the cross product of the moment arm vector and the force vector. This will result in a moment vector that has a Mx, My, and Mz components, which can be placed into their respective <math display="inline"> \sum M_x = 0, \sum M_y = 0, \sum M_z = 0,</math> equation.

The 6 equations can be rearranged into a matrix equation of the form A*X=b, which can be solved easily with linear algebra.

==See Also==
[http://scholarworks.csun.edu/bitstream/handle/10211.3/123383/Flickinger-Evan-thesis-2014.pdf;sequence=1 DESIGN AND ANALYSIS OF FORMULA SAECAR SUSPENSION MEMBERS]

[http://www.iaeme.com/MasterAdmin/uploadfolder/IJMET_07_02_018/IJMET_07_02_018.pdf FORCE CALCULATION IN UPRIGHT OF A FSAE RACE CAR]

[[Category:Suspension]]

Battery pack

2024-04-05T14:09:53Z

SpookySimon: /* Cans vs pouches */ plurality agreement

The '''battery pack''' contains the electrical potential energy used by the [[:Category:Electric_Vehicle|traction system]] and [[:Category:Electronics|onboard electronics]]. The battery pack is often referred to in industry as the rechargeable energy storage system or RESS.
==Introduction==

==Goals==
Safety & reliability should rank pretty high in design criteria as it's impossible to win a competition with a car who caught fire.


===Performance Goals===
The battery pack capacity should be sufficient to complete the desired driving cycle, frequently this is based on the endurance circuit at competition or the expected cumulative drive cycle over the course of a test day.

The battery pack should be capable of safely discharging at the commanded current rate, both peak and continuous.

The highest rate of charge is often in regenerative braking. The pack should be designed to safely accommodate the peak and continuous charge rates from regen braking.
===Design Goals===
The pack may be required to meet other goals such as packaging requirements, mass, cost, material specification, etc. These can preclude meeting design goals, particularly capacity. Correctly prioritizing team and system goals will be critical in making these compromises.
==Cell selection==
The selection process of a lithium-ion/lithium-polymer cell is highly dependent on the application. Before even starting battery pack design, it is crucial to understand the operating conditions. A light-weight car with 2WD requires less power than a heavy 4WD car with a full aero package. Because there is a trade-off between cell energy density (Wh/kg) and cell power density (W/kg)<ref>https://commons.wikimedia.org/wiki/File:Lithium_Ion_Capacitor_Chart.png</ref>, it is then possible to compare the performance of cell chemistries using lap simulation: there are cases where a higher specific energy cell is optimal, and others where high specific power is.
===Chemistry===
Most batteries used in EVs will have a lithium based chemistry. The two main lithium chemistries are nickel manganese cobalt oxides (NMC) or lithium iron phosphate (LFP). NMC batteries are an older technology, and are more common and cheaper in most configurations. While cobalt is not legally defined as a "conflict mineral", the extraction is closely tied to human suffering<ref>Dasilva, Jeremy. Conflict Implications of Rising Cobalt Demand and the Effects of Classifying Cobalt as a Conflict Mineral on the DRC. 2022. Johns Hopkins, Masters Thesis. JScholarship Library https://jscholarship.library.jhu.edu/server/api/core/bitstreams/b2780da6-5830-4b07-8a23-a5d09051b9f5/content</ref>. This alongside the relative rarity of the element has lead to a push for non-cobalt battery chemistries<ref>https://www.mitsubishicritical.com/resources/blog/the-runaway-review/lithium-nickel-manganese-cobalt/</ref>.
====NMC====
====LFP====
LFP batteries have become highly utilized in EVs due to their high performance and thermal durability. <ref>Ferreira, Summer. Thermal stability study of commercial
lithium-ion batteries as a function of
cathode chemistry and state-of-charge. 2019. https://www.osti.gov/servlets/purl/1640189</ref>

===Cans vs pouches===
The most common form factors for lithium cells are the can (i.e. 18650) or in soft metal-plastic pouches <ref>https://www.rosebatteries.com/blog/most-popular-lithium-ion-cells-for-custom-battery-packs</ref>. It is easier to design a safe battery pack with cylindrical cells as each cell is protected in a hard shell that protects them from accidental perforation. Cylindrical cells tend to offer higher energy density, while pouches tend to offer higher power density. Cylindrical cells can be spot welded together with fairly inexpensive equipment, while pouches can be connected together by ultrasonic welding, laser welding, or mechanical assembly (rivets, nuts & bolts, ...). While cylindrical cells are typically found in small capacities ( < 4 Ah ), pouches can be found in high capacities ( > 10 Ah), greatly reducing the complexity of assembly of a battery pack, since fewer cells are required to meet the battery pack energy requirement.
====Pouches====
Pouches offer better heat dissipation than other type of cells, but their flexible and thin envelope make them prone to perforation or crushing. Some pouches have tabs on the same edge, some, on opposite edges. Opposite edge tabs allow better heat dissipation, but make packaging more complex. They stack easily, using most of the available space. The cells edges are fragile: treat them with care. It is preferable to ask the cell manufacturer to have the edges taped. Most pouches will ignite in case of a nail penetration. One way to reduce the risk it would ignite is to improve the cooling of the cell. As an example, using sheets of metal between cells would spread the heat (and evacuate it out of the cell).

Pouch cells can come in larger capacities than cylindrical cells. If the capacity is large enough you may not need any parallel cell connections at all.
====Cans====
Cans can be cylindrical or prismatic. They are typically safer than pouches, since they are are valve regulated and benefits from a hard shell, reducing their perforation and crushing risk. However, it is generally harder to cool them down. Cylindrical cans also have a lower packing factor than prismatic cells leading to an effectively reduced volumetric density. However, the process of cylindrical cell fabrication is so well honed that battery packs made with state of the art cylindrical cans compare in terms of metrics with battery packs made with state of the art pouches. Cans usually also contain a positive thermal coefficient (PTC) resistor that can protect the cell in case of a short circuit. However, this protection is usually not rated for high voltage packs, can could actually ignite a fire, in a high voltage pack. Cans also can ignite when perforated. Wrapping cells with a phase change material (PCM) is one of the solutions that have been developed to absorb heat in a thermal event, reducing the odds to create a cascade event.

===Cells capacity vs safety===
At the cell level, a smaller capacity cell is safer than a higher capacity cell: a small capacity cell may not store enough energy to generate a thermal runaway. However, it is false to assume that a huge capacity pouch is more dangerous than a couple of low capacity cells put in parallel. High capacity cells are made under extremely high quality control, while low capacity 18650s are not: it's more cash efficient to discard under performing these cells. Discarding a 240 Ah cell would be extremely costly for a manufacturer. Also, high capacity cells include various safety techniques (including internal self fusing) which intent is to prevent a problematic layer of the cell to make the cell enter a thermal runway.

==Arrangement of cells==
Cells can either be connected in series (positive to negative) or parallel (positive to positive, negative to negative). Connecting cells in series raises the pack voltage, and connecting them in parallel increases the energy capacity. So if you have two 3.6V 3Ah cells, connecting them in series gets you a 7.2V 3Ah battery pack. Connecting them in parallel gets you a 3.6V 6Ah battery pack.

The cell arrangement is often labeled as "''n''S''m''P", where ''n'' is the number of cells in series and ''m'' is the number of cells in parallel. So a pack with 50 cells in series and 8 cells in parallel would be 50S8P. Multiplying ''n'' and ''m'' gives you the total number of cells in the battery pack.

Your maximum tractive system voltage will set how many cells in series you use, and you need enough energy capacity to make it through the endurance event. This is where simulations can help you decide how big of a pack you need.

===Higher voltage, or higher current?===
Simulations can tell you how many Wh your accumulator needs, which tells you how many cells you need. What the simulation can't tell you is whether to put more cells in series or more in parallel. A 6 kWh pack could be 600V and 10Ah, or it could be 60V and 100Ah. A higher voltage will also mean lower current (a 60kW draw at 600V is 100A, but at 60V it's 1000A).

====Higher voltage/lower current pack====
Pros:
* Lower current means smaller wires, less I²R heat losses.
* Smaller wires mean less weight, smaller wire bend radius
Cons:
* BMS needs to monitor more voltages
* Higher voltage means a bigger spark gap, so less safe
* Higher voltages are harder to find parts for
====Lower voltage/higher current pack====
Pros:
* Smaller BMS
* Parts rated to lower voltages can be easier to find
* Lower voltages are theoretically safer
Cons:
* Tractive system conductors (wires, etc) get bigger with the square of current (because of I²R heat losses)
* Bigger wires mean more weight and bigger bend radius

====Other possible constraints====
* The rules (max segment voltage, max segment Joules)
* Motor controller selection
* Motor selection
* Other misc. component selection (AIRs, DC-DC converter, etc.)
* Packaging constraints
* Any legacy designs from your team
* University safety policies

==Packaging==
[[File:ParapostWC.png|right|middle|thumb|Pouch Cell Module Design Example. Credits: Poly eRacing 2014 (Polytechnique Montreal)]][[File:BP.PNG|right|middle|thumb|Cylindrical Cell Battery Pack Design Example. Credits: Poly eRacing 2016 (Polytechnique Montreal)]]
A battery pack has to be designed to resists the mechanical loads and impacts it will be subjected to and the thermal conditions it may be exposed in case of a thermal runaway. Also, it must be designed considering electrical safety in mind.

Requirements may differ according to the cell type choice. Pouch cells use a thin flexible shell, which may easily by punctured. Hence, it requires an additional protection and more professional fabrication processes to protect it from being scratched, punctured, teared. Cylindrical and prismatic cells, on the other side, encapsulate the active materials in a hard shell. However, if the shell is made of a conductive material, it may require a dielectric barrier to avoid a short circuit when cells are packaged in series.
===Mechanical loads===
The battery pack must resists to impacts and vibration. Bolts need to have positive locking mechanism. The battery pack should be built strong enough in a way that cells are not crushed in case of a drop on one of its corners.
===Thermal loads===
Lithium-ion cells don't like heat. As per the rules, cells exterior casing shouldn't reach 60 Celsius. Although it's easy to circumvent the rules here, no one should do it. The heat sources may be external such as the motors, inverters, solar load, etc. or internal from heat generated by the module's internal resistance.

The internal resistances of the modules can come from the bus bars, fusing, contactors, or other power distribution components. Most likely, the largest source of internal heat generation will come from the internal resistance of the cells (DCIR). DCIR is dependent on temperature, state of health, state of charge, and discharge time <ref> https://www.batterydesign.net/battery-cell/dcir-of-a-cell/ </ref>

===Safety===
Sharp edges inside the battery pack should be avoided. Appropriate clearance between wires should be maintained. Ensure that large voltage differences are far from each other. Positive locking mechanisms should ensure that screws don't loosen. It should be impossible to create a short circuit in case of the drop of tools. Think what could go wrong in case of an accident, and try to prevent it.
====Materials====
Dielectric materials and adhesives shall be fire retardant rated and be able to sustain to high temperatures.
====Grounding====
Conductive materials in the battery pack shall be grounded.
====Segregation====
As per the rules, modules need a fire retardant confinement to avoid a fire propagation within the battery pack.
===Interconnection===
Several techniques allow the cells interconnection. They are divided in two categories: the usage of mechanical fasteners and the usage of welding.
====Fasteners====
The concept behind the usage of [[Threaded_Fasteners|fasteners]] is to compress the current tabs together. In this kind of joint, conduction increases with area and with pressure. Hence, the goal is to apply a load as uniform as possible on an area as big as possible.
=====Grease=====
With time, the interface resistance can increase, due to oxidation. One can slow down the oxidation rate with the usage of grease. Grease is actually non conductive but as little impact on overall conduction as it is squished away by the pressure. Some greases contains conductive particles in order to improve their conductivity. Examples are De-Ox or Penetrox.
====Ultrasonic welding====
Ultrasonic welding is one of the best available techniques to join different materials (as found in lithium cells). It's the recommended technique for pouch cells. However, this type of welding equipment is expensive.
====Spot welding (also known as resistance welding)====
Resistance welding is speedy and low cost. It doesn't transfer a lot of heat to cell and welding quality is good.However, conductive materials (aluminum, copper, ...) require more power to weld than resistive materials(nickel, ...). It's the recommended technique for cylindrical cells.
====Brazing or Soldering====
Brazing and soldering are generally not recommended, because the heat required to melt the brazing alloy can damage the cells components. They can also result in brittle connections that are prone to failure.

====Crimping====
Crimping cell terminal is rare but can be done with extremely simple tools.

==Possible causes of a thermal runway==
Thermal runway (i.e. battery fire) can be caused by an internal short that would be due to a poor cell design and manufacturing quality control. However, it is more likely that it is due to abuse conditions.
===Abuse conditions===

* Charging when too cold
* Charging when too hot
* Discharging when too hot
* Storage at elevated temperature
* Internal damage due to high heat when interconnecting (by soldering)
* Overcharge
* Overdischarge or charging an overdischarged cell
* Overcurrent
* Crush
* Impact or drop
* Nail penetration
* Sharp chips / dust
* Leakage current

==What to do in case of a battery fire==
===Toxicity===
Lithium batteries are toxic. Especially their electrolyte, which is flammable and contains poison salts.
===What should I do?===
In case of a fire, ensure that nobody is in danger of breathing in the smoke. If nobody is in danger, sound the fire alarm and get away. If somebody is in danger, try to save them as fast as possible so you won't get hurt yourself, as people are more important that objects. Lithium caused fires are not easy to put out, even for people that know how. Smother the fire with Sand. ABC extinguishers will not do much except give the cause the fire to slow. If it starts within your car, don't think that you can save it, as its outcome is not good after it starts. Better yet, don't let batteries you own ever get to the point of causing a fire. This is the idea when using Lithium, you must prevent the batteries from getting to that point. too much voltage or too little voltage, too much current running through, or the temperature reaching too high, each have particularly nasty consequences. For any person using lithium batteries, it is wise to read up on this technology before using, so that one can become aware of the challenges of putting out a fire caused by lithium-cell batteries.

==How to properly use a battery pack==
[[Category:Electric Vehicle]]

The proper usage of the battery shall be limited by the battery management system (BMS). Here's a list of advice:
* As per the rules, avoid exceeding 60 Celsius degree.
* Do not overcharge the cells (generally over 4.2V each), nor over discharge the cells(generally under 2.7V each).
* As per the rules, ensure that the battery pack design does not allow the drop of tools to create a short circuit.
* Ensure that all conductive materials in the battery pack is grounded.
* Ensure that all materials of the battery pack are fire retardant.
The proper storage of the battery shall be:
* In a fireproof container.
* At room temperature or cooler (< 25 Celsius degree).
* In a stable position.
* In a well ventilated area.
=References=
<references />

Battery pack

2024-04-05T14:08:36Z

SpookySimon: /* Cans vs pouches */ reference

The '''battery pack''' contains the electrical potential energy used by the [[:Category:Electric_Vehicle|traction system]] and [[:Category:Electronics|onboard electronics]]. The battery pack is often referred to in industry as the rechargeable energy storage system or RESS.
==Introduction==

==Goals==
Safety & reliability should rank pretty high in design criteria as it's impossible to win a competition with a car who caught fire.


===Performance Goals===
The battery pack capacity should be sufficient to complete the desired driving cycle, frequently this is based on the endurance circuit at competition or the expected cumulative drive cycle over the course of a test day.

The battery pack should be capable of safely discharging at the commanded current rate, both peak and continuous.

The highest rate of charge is often in regenerative braking. The pack should be designed to safely accommodate the peak and continuous charge rates from regen braking.
===Design Goals===
The pack may be required to meet other goals such as packaging requirements, mass, cost, material specification, etc. These can preclude meeting design goals, particularly capacity. Correctly prioritizing team and system goals will be critical in making these compromises.
==Cell selection==
The selection process of a lithium-ion/lithium-polymer cell is highly dependent on the application. Before even starting battery pack design, it is crucial to understand the operating conditions. A light-weight car with 2WD requires less power than a heavy 4WD car with a full aero package. Because there is a trade-off between cell energy density (Wh/kg) and cell power density (W/kg)<ref>https://commons.wikimedia.org/wiki/File:Lithium_Ion_Capacitor_Chart.png</ref>, it is then possible to compare the performance of cell chemistries using lap simulation: there are cases where a higher specific energy cell is optimal, and others where high specific power is.
===Chemistry===
Most batteries used in EVs will have a lithium based chemistry. The two main lithium chemistries are nickel manganese cobalt oxides (NMC) or lithium iron phosphate (LFP). NMC batteries are an older technology, and are more common and cheaper in most configurations. While cobalt is not legally defined as a "conflict mineral", the extraction is closely tied to human suffering<ref>Dasilva, Jeremy. Conflict Implications of Rising Cobalt Demand and the Effects of Classifying Cobalt as a Conflict Mineral on the DRC. 2022. Johns Hopkins, Masters Thesis. JScholarship Library https://jscholarship.library.jhu.edu/server/api/core/bitstreams/b2780da6-5830-4b07-8a23-a5d09051b9f5/content</ref>. This alongside the relative rarity of the element has lead to a push for non-cobalt battery chemistries<ref>https://www.mitsubishicritical.com/resources/blog/the-runaway-review/lithium-nickel-manganese-cobalt/</ref>.
====NMC====
====LFP====
LFP batteries have become highly utilized in EVs due to their high performance and thermal durability. <ref>Ferreira, Summer. Thermal stability study of commercial
lithium-ion batteries as a function of
cathode chemistry and state-of-charge. 2019. https://www.osti.gov/servlets/purl/1640189</ref>

===Cans vs pouches===
The most common form factors for lithium cells are the can (i.e. 18650) or in soft metal-plastic pouches <ref>https://www.rosebatteries.com/blog/most-popular-lithium-ion-cells-for-custom-battery-packs</ref>. It is easier to design a safe battery pack with cylindrical cells as each cells are protected in a hard shell that protects them from accidental perforation. Cylindrical cells tend to offer higher energy density, while pouches tend to offer higher power density. Cylindrical cells can be spot welded together with fairly inexpensive equipment, while pouches can be connected together by ultrasonic welding, laser welding, or mechanical assembly (rivets, nuts & bolts, ...). While cylindrical cells are typically found in small capacities ( < 4 Ah ), pouches can be found in high capacities ( > 10 Ah), greatly reducing the complexity of assembly of a battery pack, since fewer cells are required to meet the battery pack energy requirement.
====Pouches====
Pouches offer better heat dissipation than other type of cells, but their flexible and thin envelope make them prone to perforation or crushing. Some pouches have tabs on the same edge, some, on opposite edges. Opposite edge tabs allow better heat dissipation, but make packaging more complex. They stack easily, using most of the available space. The cells edges are fragile: treat them with care. It is preferable to ask the cell manufacturer to have the edges taped. Most pouches will ignite in case of a nail penetration. One way to reduce the risk it would ignite is to improve the cooling of the cell. As an example, using sheets of metal between cells would spread the heat (and evacuate it out of the cell).

Pouch cells can come in larger capacities than cylindrical cells. If the capacity is large enough you may not need any parallel cell connections at all.
====Cans====
Cans can be cylindrical or prismatic. They are typically safer than pouches, since they are are valve regulated and benefits from a hard shell, reducing their perforation and crushing risk. However, it is generally harder to cool them down. Cylindrical cans also have a lower packing factor than prismatic cells leading to an effectively reduced volumetric density. However, the process of cylindrical cell fabrication is so well honed that battery packs made with state of the art cylindrical cans compare in terms of metrics with battery packs made with state of the art pouches. Cans usually also contain a positive thermal coefficient (PTC) resistor that can protect the cell in case of a short circuit. However, this protection is usually not rated for high voltage packs, can could actually ignite a fire, in a high voltage pack. Cans also can ignite when perforated. Wrapping cells with a phase change material (PCM) is one of the solutions that have been developed to absorb heat in a thermal event, reducing the odds to create a cascade event.

===Cells capacity vs safety===
At the cell level, a smaller capacity cell is safer than a higher capacity cell: a small capacity cell may not store enough energy to generate a thermal runaway. However, it is false to assume that a huge capacity pouch is more dangerous than a couple of low capacity cells put in parallel. High capacity cells are made under extremely high quality control, while low capacity 18650s are not: it's more cash efficient to discard under performing these cells. Discarding a 240 Ah cell would be extremely costly for a manufacturer. Also, high capacity cells include various safety techniques (including internal self fusing) which intent is to prevent a problematic layer of the cell to make the cell enter a thermal runway.

==Arrangement of cells==
Cells can either be connected in series (positive to negative) or parallel (positive to positive, negative to negative). Connecting cells in series raises the pack voltage, and connecting them in parallel increases the energy capacity. So if you have two 3.6V 3Ah cells, connecting them in series gets you a 7.2V 3Ah battery pack. Connecting them in parallel gets you a 3.6V 6Ah battery pack.

The cell arrangement is often labeled as "''n''S''m''P", where ''n'' is the number of cells in series and ''m'' is the number of cells in parallel. So a pack with 50 cells in series and 8 cells in parallel would be 50S8P. Multiplying ''n'' and ''m'' gives you the total number of cells in the battery pack.

Your maximum tractive system voltage will set how many cells in series you use, and you need enough energy capacity to make it through the endurance event. This is where simulations can help you decide how big of a pack you need.

===Higher voltage, or higher current?===
Simulations can tell you how many Wh your accumulator needs, which tells you how many cells you need. What the simulation can't tell you is whether to put more cells in series or more in parallel. A 6 kWh pack could be 600V and 10Ah, or it could be 60V and 100Ah. A higher voltage will also mean lower current (a 60kW draw at 600V is 100A, but at 60V it's 1000A).

====Higher voltage/lower current pack====
Pros:
* Lower current means smaller wires, less I²R heat losses.
* Smaller wires mean less weight, smaller wire bend radius
Cons:
* BMS needs to monitor more voltages
* Higher voltage means a bigger spark gap, so less safe
* Higher voltages are harder to find parts for
====Lower voltage/higher current pack====
Pros:
* Smaller BMS
* Parts rated to lower voltages can be easier to find
* Lower voltages are theoretically safer
Cons:
* Tractive system conductors (wires, etc) get bigger with the square of current (because of I²R heat losses)
* Bigger wires mean more weight and bigger bend radius

====Other possible constraints====
* The rules (max segment voltage, max segment Joules)
* Motor controller selection
* Motor selection
* Other misc. component selection (AIRs, DC-DC converter, etc.)
* Packaging constraints
* Any legacy designs from your team
* University safety policies

==Packaging==
[[File:ParapostWC.png|right|middle|thumb|Pouch Cell Module Design Example. Credits: Poly eRacing 2014 (Polytechnique Montreal)]][[File:BP.PNG|right|middle|thumb|Cylindrical Cell Battery Pack Design Example. Credits: Poly eRacing 2016 (Polytechnique Montreal)]]
A battery pack has to be designed to resists the mechanical loads and impacts it will be subjected to and the thermal conditions it may be exposed in case of a thermal runaway. Also, it must be designed considering electrical safety in mind.

Requirements may differ according to the cell type choice. Pouch cells use a thin flexible shell, which may easily by punctured. Hence, it requires an additional protection and more professional fabrication processes to protect it from being scratched, punctured, teared. Cylindrical and prismatic cells, on the other side, encapsulate the active materials in a hard shell. However, if the shell is made of a conductive material, it may require a dielectric barrier to avoid a short circuit when cells are packaged in series.
===Mechanical loads===
The battery pack must resists to impacts and vibration. Bolts need to have positive locking mechanism. The battery pack should be built strong enough in a way that cells are not crushed in case of a drop on one of its corners.
===Thermal loads===
Lithium-ion cells don't like heat. As per the rules, cells exterior casing shouldn't reach 60 Celsius. Although it's easy to circumvent the rules here, no one should do it. The heat sources may be external such as the motors, inverters, solar load, etc. or internal from heat generated by the module's internal resistance.

The internal resistances of the modules can come from the bus bars, fusing, contactors, or other power distribution components. Most likely, the largest source of internal heat generation will come from the internal resistance of the cells (DCIR). DCIR is dependent on temperature, state of health, state of charge, and discharge time <ref> https://www.batterydesign.net/battery-cell/dcir-of-a-cell/ </ref>

===Safety===
Sharp edges inside the battery pack should be avoided. Appropriate clearance between wires should be maintained. Ensure that large voltage differences are far from each other. Positive locking mechanisms should ensure that screws don't loosen. It should be impossible to create a short circuit in case of the drop of tools. Think what could go wrong in case of an accident, and try to prevent it.
====Materials====
Dielectric materials and adhesives shall be fire retardant rated and be able to sustain to high temperatures.
====Grounding====
Conductive materials in the battery pack shall be grounded.
====Segregation====
As per the rules, modules need a fire retardant confinement to avoid a fire propagation within the battery pack.
===Interconnection===
Several techniques allow the cells interconnection. They are divided in two categories: the usage of mechanical fasteners and the usage of welding.
====Fasteners====
The concept behind the usage of [[Threaded_Fasteners|fasteners]] is to compress the current tabs together. In this kind of joint, conduction increases with area and with pressure. Hence, the goal is to apply a load as uniform as possible on an area as big as possible.
=====Grease=====
With time, the interface resistance can increase, due to oxidation. One can slow down the oxidation rate with the usage of grease. Grease is actually non conductive but as little impact on overall conduction as it is squished away by the pressure. Some greases contains conductive particles in order to improve their conductivity. Examples are De-Ox or Penetrox.
====Ultrasonic welding====
Ultrasonic welding is one of the best available techniques to join different materials (as found in lithium cells). It's the recommended technique for pouch cells. However, this type of welding equipment is expensive.
====Spot welding (also known as resistance welding)====
Resistance welding is speedy and low cost. It doesn't transfer a lot of heat to cell and welding quality is good.However, conductive materials (aluminum, copper, ...) require more power to weld than resistive materials(nickel, ...). It's the recommended technique for cylindrical cells.
====Brazing or Soldering====
Brazing and soldering are generally not recommended, because the heat required to melt the brazing alloy can damage the cells components. They can also result in brittle connections that are prone to failure.

====Crimping====
Crimping cell terminal is rare but can be done with extremely simple tools.

==Possible causes of a thermal runway==
Thermal runway (i.e. battery fire) can be caused by an internal short that would be due to a poor cell design and manufacturing quality control. However, it is more likely that it is due to abuse conditions.
===Abuse conditions===

* Charging when too cold
* Charging when too hot
* Discharging when too hot
* Storage at elevated temperature
* Internal damage due to high heat when interconnecting (by soldering)
* Overcharge
* Overdischarge or charging an overdischarged cell
* Overcurrent
* Crush
* Impact or drop
* Nail penetration
* Sharp chips / dust
* Leakage current

==What to do in case of a battery fire==
===Toxicity===
Lithium batteries are toxic. Especially their electrolyte, which is flammable and contains poison salts.
===What should I do?===
In case of a fire, ensure that nobody is in danger of breathing in the smoke. If nobody is in danger, sound the fire alarm and get away. If somebody is in danger, try to save them as fast as possible so you won't get hurt yourself, as people are more important that objects. Lithium caused fires are not easy to put out, even for people that know how. Smother the fire with Sand. ABC extinguishers will not do much except give the cause the fire to slow. If it starts within your car, don't think that you can save it, as its outcome is not good after it starts. Better yet, don't let batteries you own ever get to the point of causing a fire. This is the idea when using Lithium, you must prevent the batteries from getting to that point. too much voltage or too little voltage, too much current running through, or the temperature reaching too high, each have particularly nasty consequences. For any person using lithium batteries, it is wise to read up on this technology before using, so that one can become aware of the challenges of putting out a fire caused by lithium-cell batteries.

==How to properly use a battery pack==
[[Category:Electric Vehicle]]

The proper usage of the battery shall be limited by the battery management system (BMS). Here's a list of advice:
* As per the rules, avoid exceeding 60 Celsius degree.
* Do not overcharge the cells (generally over 4.2V each), nor over discharge the cells(generally under 2.7V each).
* As per the rules, ensure that the battery pack design does not allow the drop of tools to create a short circuit.
* Ensure that all conductive materials in the battery pack is grounded.
* Ensure that all materials of the battery pack are fire retardant.
The proper storage of the battery shall be:
* In a fireproof container.
* At room temperature or cooler (< 25 Celsius degree).
* In a stable position.
* In a well ventilated area.
=References=
<references />

Battery pack

2024-04-05T14:07:10Z

SpookySimon: /* LFP */ reference

The '''battery pack''' contains the electrical potential energy used by the [[:Category:Electric_Vehicle|traction system]] and [[:Category:Electronics|onboard electronics]]. The battery pack is often referred to in industry as the rechargeable energy storage system or RESS.
==Introduction==

==Goals==
Safety & reliability should rank pretty high in design criteria as it's impossible to win a competition with a car who caught fire.


===Performance Goals===
The battery pack capacity should be sufficient to complete the desired driving cycle, frequently this is based on the endurance circuit at competition or the expected cumulative drive cycle over the course of a test day.

The battery pack should be capable of safely discharging at the commanded current rate, both peak and continuous.

The highest rate of charge is often in regenerative braking. The pack should be designed to safely accommodate the peak and continuous charge rates from regen braking.
===Design Goals===
The pack may be required to meet other goals such as packaging requirements, mass, cost, material specification, etc. These can preclude meeting design goals, particularly capacity. Correctly prioritizing team and system goals will be critical in making these compromises.
==Cell selection==
The selection process of a lithium-ion/lithium-polymer cell is highly dependent on the application. Before even starting battery pack design, it is crucial to understand the operating conditions. A light-weight car with 2WD requires less power than a heavy 4WD car with a full aero package. Because there is a trade-off between cell energy density (Wh/kg) and cell power density (W/kg)<ref>https://commons.wikimedia.org/wiki/File:Lithium_Ion_Capacitor_Chart.png</ref>, it is then possible to compare the performance of cell chemistries using lap simulation: there are cases where a higher specific energy cell is optimal, and others where high specific power is.
===Chemistry===
Most batteries used in EVs will have a lithium based chemistry. The two main lithium chemistries are nickel manganese cobalt oxides (NMC) or lithium iron phosphate (LFP). NMC batteries are an older technology, and are more common and cheaper in most configurations. While cobalt is not legally defined as a "conflict mineral", the extraction is closely tied to human suffering<ref>Dasilva, Jeremy. Conflict Implications of Rising Cobalt Demand and the Effects of Classifying Cobalt as a Conflict Mineral on the DRC. 2022. Johns Hopkins, Masters Thesis. JScholarship Library https://jscholarship.library.jhu.edu/server/api/core/bitstreams/b2780da6-5830-4b07-8a23-a5d09051b9f5/content</ref>. This alongside the relative rarity of the element has lead to a push for non-cobalt battery chemistries<ref>https://www.mitsubishicritical.com/resources/blog/the-runaway-review/lithium-nickel-manganese-cobalt/</ref>.
====NMC====
====LFP====
LFP batteries have become highly utilized in EVs due to their high performance and thermal durability. <ref>Ferreira, Summer. Thermal stability study of commercial
lithium-ion batteries as a function of
cathode chemistry and state-of-charge. 2019. https://www.osti.gov/servlets/purl/1640189</ref>

===Cans vs pouches===
The most common form factors for lithium cells are the can (i.e. 18650) or in soft metal-plastic pouches. It is easier to design a safe battery pack with cylindrical cells as each cells are protected in a hard shell that protects them from accidental perforation. Cylindrical cells tend to offer higher energy density, while pouches tend to offer higher power density. Cylindrical cells can be spot welded together with fairly inexpensive equipment, while pouches can be connected together by ultrasonic welding, laser welding, or mechanical assembly (rivets, nuts & bolts, ...). While cylindrical cells are typically found in small capacities ( < 4 Ah ), pouches can be found in high capacities ( > 10 Ah), greatly reducing the complexity of assembly of a battery pack, since fewer cells are required to meet the battery pack energy requirement.
====Pouches====
Pouches offer better heat dissipation than other type of cells, but their flexible and thin envelope make them prone to perforation or crushing. Some pouches have tabs on the same edge, some, on opposite edges. Opposite edge tabs allow better heat dissipation, but make packaging more complex. They stack easily, using most of the available space. The cells edges are fragile: treat them with care. It is preferable to ask the cell manufacturer to have the edges taped. Most pouches will ignite in case of a nail penetration. One way to reduce the risk it would ignite is to improve the cooling of the cell. As an example, using sheets of metal between cells would spread the heat (and evacuate it out of the cell).

Pouch cells can come in larger capacities than cylindrical cells. If the capacity is large enough you may not need any parallel cell connections at all.
====Cans====
Cans can be cylindrical or prismatic. They are typically safer than pouches, since they are are valve regulated and benefits from a hard shell, reducing their perforation and crushing risk. However, it is generally harder to cool them down. Cylindrical cans also have a lower packing factor than prismatic cells leading to an effectively reduced volumetric density. However, the process of cylindrical cell fabrication is so well honed that battery packs made with state of the art cylindrical cans compare in terms of metrics with battery packs made with state of the art pouches. Cans usually also contain a positive thermal coefficient (PTC) resistor that can protect the cell in case of a short circuit. However, this protection is usually not rated for high voltage packs, can could actually ignite a fire, in a high voltage pack. Cans also can ignite when perforated. Wrapping cells with a phase change material (PCM) is one of the solutions that have been developed to absorb heat in a thermal event, reducing the odds to create a cascade event.

===Cells capacity vs safety===
At the cell level, a smaller capacity cell is safer than a higher capacity cell: a small capacity cell may not store enough energy to generate a thermal runaway. However, it is false to assume that a huge capacity pouch is more dangerous than a couple of low capacity cells put in parallel. High capacity cells are made under extremely high quality control, while low capacity 18650s are not: it's more cash efficient to discard under performing these cells. Discarding a 240 Ah cell would be extremely costly for a manufacturer. Also, high capacity cells include various safety techniques (including internal self fusing) which intent is to prevent a problematic layer of the cell to make the cell enter a thermal runway.

==Arrangement of cells==
Cells can either be connected in series (positive to negative) or parallel (positive to positive, negative to negative). Connecting cells in series raises the pack voltage, and connecting them in parallel increases the energy capacity. So if you have two 3.6V 3Ah cells, connecting them in series gets you a 7.2V 3Ah battery pack. Connecting them in parallel gets you a 3.6V 6Ah battery pack.

The cell arrangement is often labeled as "''n''S''m''P", where ''n'' is the number of cells in series and ''m'' is the number of cells in parallel. So a pack with 50 cells in series and 8 cells in parallel would be 50S8P. Multiplying ''n'' and ''m'' gives you the total number of cells in the battery pack.

Your maximum tractive system voltage will set how many cells in series you use, and you need enough energy capacity to make it through the endurance event. This is where simulations can help you decide how big of a pack you need.

===Higher voltage, or higher current?===
Simulations can tell you how many Wh your accumulator needs, which tells you how many cells you need. What the simulation can't tell you is whether to put more cells in series or more in parallel. A 6 kWh pack could be 600V and 10Ah, or it could be 60V and 100Ah. A higher voltage will also mean lower current (a 60kW draw at 600V is 100A, but at 60V it's 1000A).

====Higher voltage/lower current pack====
Pros:
* Lower current means smaller wires, less I²R heat losses.
* Smaller wires mean less weight, smaller wire bend radius
Cons:
* BMS needs to monitor more voltages
* Higher voltage means a bigger spark gap, so less safe
* Higher voltages are harder to find parts for
====Lower voltage/higher current pack====
Pros:
* Smaller BMS
* Parts rated to lower voltages can be easier to find
* Lower voltages are theoretically safer
Cons:
* Tractive system conductors (wires, etc) get bigger with the square of current (because of I²R heat losses)
* Bigger wires mean more weight and bigger bend radius

====Other possible constraints====
* The rules (max segment voltage, max segment Joules)
* Motor controller selection
* Motor selection
* Other misc. component selection (AIRs, DC-DC converter, etc.)
* Packaging constraints
* Any legacy designs from your team
* University safety policies

==Packaging==
[[File:ParapostWC.png|right|middle|thumb|Pouch Cell Module Design Example. Credits: Poly eRacing 2014 (Polytechnique Montreal)]][[File:BP.PNG|right|middle|thumb|Cylindrical Cell Battery Pack Design Example. Credits: Poly eRacing 2016 (Polytechnique Montreal)]]
A battery pack has to be designed to resists the mechanical loads and impacts it will be subjected to and the thermal conditions it may be exposed in case of a thermal runaway. Also, it must be designed considering electrical safety in mind.

Requirements may differ according to the cell type choice. Pouch cells use a thin flexible shell, which may easily by punctured. Hence, it requires an additional protection and more professional fabrication processes to protect it from being scratched, punctured, teared. Cylindrical and prismatic cells, on the other side, encapsulate the active materials in a hard shell. However, if the shell is made of a conductive material, it may require a dielectric barrier to avoid a short circuit when cells are packaged in series.
===Mechanical loads===
The battery pack must resists to impacts and vibration. Bolts need to have positive locking mechanism. The battery pack should be built strong enough in a way that cells are not crushed in case of a drop on one of its corners.
===Thermal loads===
Lithium-ion cells don't like heat. As per the rules, cells exterior casing shouldn't reach 60 Celsius. Although it's easy to circumvent the rules here, no one should do it. The heat sources may be external such as the motors, inverters, solar load, etc. or internal from heat generated by the module's internal resistance.

The internal resistances of the modules can come from the bus bars, fusing, contactors, or other power distribution components. Most likely, the largest source of internal heat generation will come from the internal resistance of the cells (DCIR). DCIR is dependent on temperature, state of health, state of charge, and discharge time <ref> https://www.batterydesign.net/battery-cell/dcir-of-a-cell/ </ref>

===Safety===
Sharp edges inside the battery pack should be avoided. Appropriate clearance between wires should be maintained. Ensure that large voltage differences are far from each other. Positive locking mechanisms should ensure that screws don't loosen. It should be impossible to create a short circuit in case of the drop of tools. Think what could go wrong in case of an accident, and try to prevent it.
====Materials====
Dielectric materials and adhesives shall be fire retardant rated and be able to sustain to high temperatures.
====Grounding====
Conductive materials in the battery pack shall be grounded.
====Segregation====
As per the rules, modules need a fire retardant confinement to avoid a fire propagation within the battery pack.
===Interconnection===
Several techniques allow the cells interconnection. They are divided in two categories: the usage of mechanical fasteners and the usage of welding.
====Fasteners====
The concept behind the usage of [[Threaded_Fasteners|fasteners]] is to compress the current tabs together. In this kind of joint, conduction increases with area and with pressure. Hence, the goal is to apply a load as uniform as possible on an area as big as possible.
=====Grease=====
With time, the interface resistance can increase, due to oxidation. One can slow down the oxidation rate with the usage of grease. Grease is actually non conductive but as little impact on overall conduction as it is squished away by the pressure. Some greases contains conductive particles in order to improve their conductivity. Examples are De-Ox or Penetrox.
====Ultrasonic welding====
Ultrasonic welding is one of the best available techniques to join different materials (as found in lithium cells). It's the recommended technique for pouch cells. However, this type of welding equipment is expensive.
====Spot welding (also known as resistance welding)====
Resistance welding is speedy and low cost. It doesn't transfer a lot of heat to cell and welding quality is good.However, conductive materials (aluminum, copper, ...) require more power to weld than resistive materials(nickel, ...). It's the recommended technique for cylindrical cells.
====Brazing or Soldering====
Brazing and soldering are generally not recommended, because the heat required to melt the brazing alloy can damage the cells components. They can also result in brittle connections that are prone to failure.

====Crimping====
Crimping cell terminal is rare but can be done with extremely simple tools.

==Possible causes of a thermal runway==
Thermal runway (i.e. battery fire) can be caused by an internal short that would be due to a poor cell design and manufacturing quality control. However, it is more likely that it is due to abuse conditions.
===Abuse conditions===

* Charging when too cold
* Charging when too hot
* Discharging when too hot
* Storage at elevated temperature
* Internal damage due to high heat when interconnecting (by soldering)
* Overcharge
* Overdischarge or charging an overdischarged cell
* Overcurrent
* Crush
* Impact or drop
* Nail penetration
* Sharp chips / dust
* Leakage current

==What to do in case of a battery fire==
===Toxicity===
Lithium batteries are toxic. Especially their electrolyte, which is flammable and contains poison salts.
===What should I do?===
In case of a fire, ensure that nobody is in danger of breathing in the smoke. If nobody is in danger, sound the fire alarm and get away. If somebody is in danger, try to save them as fast as possible so you won't get hurt yourself, as people are more important that objects. Lithium caused fires are not easy to put out, even for people that know how. Smother the fire with Sand. ABC extinguishers will not do much except give the cause the fire to slow. If it starts within your car, don't think that you can save it, as its outcome is not good after it starts. Better yet, don't let batteries you own ever get to the point of causing a fire. This is the idea when using Lithium, you must prevent the batteries from getting to that point. too much voltage or too little voltage, too much current running through, or the temperature reaching too high, each have particularly nasty consequences. For any person using lithium batteries, it is wise to read up on this technology before using, so that one can become aware of the challenges of putting out a fire caused by lithium-cell batteries.

==How to properly use a battery pack==
[[Category:Electric Vehicle]]

The proper usage of the battery shall be limited by the battery management system (BMS). Here's a list of advice:
* As per the rules, avoid exceeding 60 Celsius degree.
* Do not overcharge the cells (generally over 4.2V each), nor over discharge the cells(generally under 2.7V each).
* As per the rules, ensure that the battery pack design does not allow the drop of tools to create a short circuit.
* Ensure that all conductive materials in the battery pack is grounded.
* Ensure that all materials of the battery pack are fire retardant.
The proper storage of the battery shall be:
* In a fireproof container.
* At room temperature or cooler (< 25 Celsius degree).
* In a stable position.
* In a well ventilated area.
=References=
<references />

Battery pack

2024-04-05T14:02:17Z

SpookySimon: /* Cell selection */ reference

The '''battery pack''' contains the electrical potential energy used by the [[:Category:Electric_Vehicle|traction system]] and [[:Category:Electronics|onboard electronics]]. The battery pack is often referred to in industry as the rechargeable energy storage system or RESS.
==Introduction==

==Goals==
Safety & reliability should rank pretty high in design criteria as it's impossible to win a competition with a car who caught fire.


===Performance Goals===
The battery pack capacity should be sufficient to complete the desired driving cycle, frequently this is based on the endurance circuit at competition or the expected cumulative drive cycle over the course of a test day.

The battery pack should be capable of safely discharging at the commanded current rate, both peak and continuous.

The highest rate of charge is often in regenerative braking. The pack should be designed to safely accommodate the peak and continuous charge rates from regen braking.
===Design Goals===
The pack may be required to meet other goals such as packaging requirements, mass, cost, material specification, etc. These can preclude meeting design goals, particularly capacity. Correctly prioritizing team and system goals will be critical in making these compromises.
==Cell selection==
The selection process of a lithium-ion/lithium-polymer cell is highly dependent on the application. Before even starting battery pack design, it is crucial to understand the operating conditions. A light-weight car with 2WD requires less power than a heavy 4WD car with a full aero package. Because there is a trade-off between cell energy density (Wh/kg) and cell power density (W/kg)<ref>https://commons.wikimedia.org/wiki/File:Lithium_Ion_Capacitor_Chart.png</ref>, it is then possible to compare the performance of cell chemistries using lap simulation: there are cases where a higher specific energy cell is optimal, and others where high specific power is.
===Chemistry===
Most batteries used in EVs will have a lithium based chemistry. The two main lithium chemistries are nickel manganese cobalt oxides (NMC) or lithium iron phosphate (LFP). NMC batteries are an older technology, and are more common and cheaper in most configurations. While cobalt is not legally defined as a "conflict mineral", the extraction is closely tied to human suffering<ref>Dasilva, Jeremy. Conflict Implications of Rising Cobalt Demand and the Effects of Classifying Cobalt as a Conflict Mineral on the DRC. 2022. Johns Hopkins, Masters Thesis. JScholarship Library https://jscholarship.library.jhu.edu/server/api/core/bitstreams/b2780da6-5830-4b07-8a23-a5d09051b9f5/content</ref>. This alongside the relative rarity of the element has lead to a push for non-cobalt battery chemistries<ref>https://www.mitsubishicritical.com/resources/blog/the-runaway-review/lithium-nickel-manganese-cobalt/</ref>.
====NMC====
====LFP====
LFP batteries have become highly utilized in EVs due to their high performance and thermal durability.

===Cans vs pouches===
The most common form factors for lithium cells are the can (i.e. 18650) or in soft metal-plastic pouches. It is easier to design a safe battery pack with cylindrical cells as each cells are protected in a hard shell that protects them from accidental perforation. Cylindrical cells tend to offer higher energy density, while pouches tend to offer higher power density. Cylindrical cells can be spot welded together with fairly inexpensive equipment, while pouches can be connected together by ultrasonic welding, laser welding, or mechanical assembly (rivets, nuts & bolts, ...). While cylindrical cells are typically found in small capacities ( < 4 Ah ), pouches can be found in high capacities ( > 10 Ah), greatly reducing the complexity of assembly of a battery pack, since fewer cells are required to meet the battery pack energy requirement.
====Pouches====
Pouches offer better heat dissipation than other type of cells, but their flexible and thin envelope make them prone to perforation or crushing. Some pouches have tabs on the same edge, some, on opposite edges. Opposite edge tabs allow better heat dissipation, but make packaging more complex. They stack easily, using most of the available space. The cells edges are fragile: treat them with care. It is preferable to ask the cell manufacturer to have the edges taped. Most pouches will ignite in case of a nail penetration. One way to reduce the risk it would ignite is to improve the cooling of the cell. As an example, using sheets of metal between cells would spread the heat (and evacuate it out of the cell).

Pouch cells can come in larger capacities than cylindrical cells. If the capacity is large enough you may not need any parallel cell connections at all.
====Cans====
Cans can be cylindrical or prismatic. They are typically safer than pouches, since they are are valve regulated and benefits from a hard shell, reducing their perforation and crushing risk. However, it is generally harder to cool them down. Cylindrical cans also have a lower packing factor than prismatic cells leading to an effectively reduced volumetric density. However, the process of cylindrical cell fabrication is so well honed that battery packs made with state of the art cylindrical cans compare in terms of metrics with battery packs made with state of the art pouches. Cans usually also contain a positive thermal coefficient (PTC) resistor that can protect the cell in case of a short circuit. However, this protection is usually not rated for high voltage packs, can could actually ignite a fire, in a high voltage pack. Cans also can ignite when perforated. Wrapping cells with a phase change material (PCM) is one of the solutions that have been developed to absorb heat in a thermal event, reducing the odds to create a cascade event.

===Cells capacity vs safety===
At the cell level, a smaller capacity cell is safer than a higher capacity cell: a small capacity cell may not store enough energy to generate a thermal runaway. However, it is false to assume that a huge capacity pouch is more dangerous than a couple of low capacity cells put in parallel. High capacity cells are made under extremely high quality control, while low capacity 18650s are not: it's more cash efficient to discard under performing these cells. Discarding a 240 Ah cell would be extremely costly for a manufacturer. Also, high capacity cells include various safety techniques (including internal self fusing) which intent is to prevent a problematic layer of the cell to make the cell enter a thermal runway.

==Arrangement of cells==
Cells can either be connected in series (positive to negative) or parallel (positive to positive, negative to negative). Connecting cells in series raises the pack voltage, and connecting them in parallel increases the energy capacity. So if you have two 3.6V 3Ah cells, connecting them in series gets you a 7.2V 3Ah battery pack. Connecting them in parallel gets you a 3.6V 6Ah battery pack.

The cell arrangement is often labeled as "''n''S''m''P", where ''n'' is the number of cells in series and ''m'' is the number of cells in parallel. So a pack with 50 cells in series and 8 cells in parallel would be 50S8P. Multiplying ''n'' and ''m'' gives you the total number of cells in the battery pack.

Your maximum tractive system voltage will set how many cells in series you use, and you need enough energy capacity to make it through the endurance event. This is where simulations can help you decide how big of a pack you need.

===Higher voltage, or higher current?===
Simulations can tell you how many Wh your accumulator needs, which tells you how many cells you need. What the simulation can't tell you is whether to put more cells in series or more in parallel. A 6 kWh pack could be 600V and 10Ah, or it could be 60V and 100Ah. A higher voltage will also mean lower current (a 60kW draw at 600V is 100A, but at 60V it's 1000A).

====Higher voltage/lower current pack====
Pros:
* Lower current means smaller wires, less I²R heat losses.
* Smaller wires mean less weight, smaller wire bend radius
Cons:
* BMS needs to monitor more voltages
* Higher voltage means a bigger spark gap, so less safe
* Higher voltages are harder to find parts for
====Lower voltage/higher current pack====
Pros:
* Smaller BMS
* Parts rated to lower voltages can be easier to find
* Lower voltages are theoretically safer
Cons:
* Tractive system conductors (wires, etc) get bigger with the square of current (because of I²R heat losses)
* Bigger wires mean more weight and bigger bend radius

====Other possible constraints====
* The rules (max segment voltage, max segment Joules)
* Motor controller selection
* Motor selection
* Other misc. component selection (AIRs, DC-DC converter, etc.)
* Packaging constraints
* Any legacy designs from your team
* University safety policies

==Packaging==
[[File:ParapostWC.png|right|middle|thumb|Pouch Cell Module Design Example. Credits: Poly eRacing 2014 (Polytechnique Montreal)]][[File:BP.PNG|right|middle|thumb|Cylindrical Cell Battery Pack Design Example. Credits: Poly eRacing 2016 (Polytechnique Montreal)]]
A battery pack has to be designed to resists the mechanical loads and impacts it will be subjected to and the thermal conditions it may be exposed in case of a thermal runaway. Also, it must be designed considering electrical safety in mind.

Requirements may differ according to the cell type choice. Pouch cells use a thin flexible shell, which may easily by punctured. Hence, it requires an additional protection and more professional fabrication processes to protect it from being scratched, punctured, teared. Cylindrical and prismatic cells, on the other side, encapsulate the active materials in a hard shell. However, if the shell is made of a conductive material, it may require a dielectric barrier to avoid a short circuit when cells are packaged in series.
===Mechanical loads===
The battery pack must resists to impacts and vibration. Bolts need to have positive locking mechanism. The battery pack should be built strong enough in a way that cells are not crushed in case of a drop on one of its corners.
===Thermal loads===
Lithium-ion cells don't like heat. As per the rules, cells exterior casing shouldn't reach 60 Celsius. Although it's easy to circumvent the rules here, no one should do it. The heat sources may be external such as the motors, inverters, solar load, etc. or internal from heat generated by the module's internal resistance.

The internal resistances of the modules can come from the bus bars, fusing, contactors, or other power distribution components. Most likely, the largest source of internal heat generation will come from the internal resistance of the cells (DCIR). DCIR is dependent on temperature, state of health, state of charge, and discharge time <ref> https://www.batterydesign.net/battery-cell/dcir-of-a-cell/ </ref>

===Safety===
Sharp edges inside the battery pack should be avoided. Appropriate clearance between wires should be maintained. Ensure that large voltage differences are far from each other. Positive locking mechanisms should ensure that screws don't loosen. It should be impossible to create a short circuit in case of the drop of tools. Think what could go wrong in case of an accident, and try to prevent it.
====Materials====
Dielectric materials and adhesives shall be fire retardant rated and be able to sustain to high temperatures.
====Grounding====
Conductive materials in the battery pack shall be grounded.
====Segregation====
As per the rules, modules need a fire retardant confinement to avoid a fire propagation within the battery pack.
===Interconnection===
Several techniques allow the cells interconnection. They are divided in two categories: the usage of mechanical fasteners and the usage of welding.
====Fasteners====
The concept behind the usage of [[Threaded_Fasteners|fasteners]] is to compress the current tabs together. In this kind of joint, conduction increases with area and with pressure. Hence, the goal is to apply a load as uniform as possible on an area as big as possible.
=====Grease=====
With time, the interface resistance can increase, due to oxidation. One can slow down the oxidation rate with the usage of grease. Grease is actually non conductive but as little impact on overall conduction as it is squished away by the pressure. Some greases contains conductive particles in order to improve their conductivity. Examples are De-Ox or Penetrox.
====Ultrasonic welding====
Ultrasonic welding is one of the best available techniques to join different materials (as found in lithium cells). It's the recommended technique for pouch cells. However, this type of welding equipment is expensive.
====Spot welding (also known as resistance welding)====
Resistance welding is speedy and low cost. It doesn't transfer a lot of heat to cell and welding quality is good.However, conductive materials (aluminum, copper, ...) require more power to weld than resistive materials(nickel, ...). It's the recommended technique for cylindrical cells.
====Brazing or Soldering====
Brazing and soldering are generally not recommended, because the heat required to melt the brazing alloy can damage the cells components. They can also result in brittle connections that are prone to failure.

====Crimping====
Crimping cell terminal is rare but can be done with extremely simple tools.

==Possible causes of a thermal runway==
Thermal runway (i.e. battery fire) can be caused by an internal short that would be due to a poor cell design and manufacturing quality control. However, it is more likely that it is due to abuse conditions.
===Abuse conditions===

* Charging when too cold
* Charging when too hot
* Discharging when too hot
* Storage at elevated temperature
* Internal damage due to high heat when interconnecting (by soldering)
* Overcharge
* Overdischarge or charging an overdischarged cell
* Overcurrent
* Crush
* Impact or drop
* Nail penetration
* Sharp chips / dust
* Leakage current

==What to do in case of a battery fire==
===Toxicity===
Lithium batteries are toxic. Especially their electrolyte, which is flammable and contains poison salts.
===What should I do?===
In case of a fire, ensure that nobody is in danger of breathing in the smoke. If nobody is in danger, sound the fire alarm and get away. If somebody is in danger, try to save them as fast as possible so you won't get hurt yourself, as people are more important that objects. Lithium caused fires are not easy to put out, even for people that know how. Smother the fire with Sand. ABC extinguishers will not do much except give the cause the fire to slow. If it starts within your car, don't think that you can save it, as its outcome is not good after it starts. Better yet, don't let batteries you own ever get to the point of causing a fire. This is the idea when using Lithium, you must prevent the batteries from getting to that point. too much voltage or too little voltage, too much current running through, or the temperature reaching too high, each have particularly nasty consequences. For any person using lithium batteries, it is wise to read up on this technology before using, so that one can become aware of the challenges of putting out a fire caused by lithium-cell batteries.

==How to properly use a battery pack==
[[Category:Electric Vehicle]]

The proper usage of the battery shall be limited by the battery management system (BMS). Here's a list of advice:
* As per the rules, avoid exceeding 60 Celsius degree.
* Do not overcharge the cells (generally over 4.2V each), nor over discharge the cells(generally under 2.7V each).
* As per the rules, ensure that the battery pack design does not allow the drop of tools to create a short circuit.
* Ensure that all conductive materials in the battery pack is grounded.
* Ensure that all materials of the battery pack are fire retardant.
The proper storage of the battery shall be:
* In a fireproof container.
* At room temperature or cooler (< 25 Celsius degree).
* In a stable position.
* In a well ventilated area.
=References=
<references />

Battery pack

2024-04-05T13:48:24Z

SpookySimon: /* Chemistry */ intro to lfp.. this will probably need a lot of work

The '''battery pack''' contains the electrical potential energy used by the [[:Category:Electric_Vehicle|traction system]] and [[:Category:Electronics|onboard electronics]]. The battery pack is often referred to in industry as the rechargeable energy storage system or RESS.
==Introduction==

==Goals==
Safety & reliability should rank pretty high in design criteria as it's impossible to win a competition with a car who caught fire.


===Performance Goals===
The battery pack capacity should be sufficient to complete the desired driving cycle, frequently this is based on the endurance circuit at competition or the expected cumulative drive cycle over the course of a test day.

The battery pack should be capable of safely discharging at the commanded current rate, both peak and continuous.

The highest rate of charge is often in regenerative braking. The pack should be designed to safely accommodate the peak and continuous charge rates from regen braking.
===Design Goals===
The pack may be required to meet other goals such as packaging requirements, mass, cost, material specification, etc. These can preclude meeting design goals, particularly capacity. Correctly prioritizing team and system goals will be critical in making these compromises.
==Cell selection==
The selection process of a lithium-ion/lithium-polymer cell is highly dependent on the application. Before even starting battery pack design, it is crucial to understand the operating conditions. A light-weight car with 2WD requires less power than a heavy 4WD car with a full aero package. Because there is a trade-off between cell energy density (Wh/kg) and cell power density (W/kg), it is then possible to compare the performance of cell chemistries using lap simulation: there are cases where a higher specific energy cell is optimal, and others where high specific power is.
===Chemistry===
Most batteries used in EVs will have a lithium based chemistry. The two main lithium chemistries are nickel manganese cobalt oxides (NMC) or lithium iron phosphate (LFP). NMC batteries are an older technology, and are more common and cheaper in most configurations. While cobalt is not legally defined as a "conflict mineral", the extraction is closely tied to human suffering<ref>Dasilva, Jeremy. Conflict Implications of Rising Cobalt Demand and the Effects of Classifying Cobalt as a Conflict Mineral on the DRC. 2022. Johns Hopkins, Masters Thesis. JScholarship Library https://jscholarship.library.jhu.edu/server/api/core/bitstreams/b2780da6-5830-4b07-8a23-a5d09051b9f5/content</ref>. This alongside the relative rarity of the element has lead to a push for non-cobalt battery chemistries<ref>https://www.mitsubishicritical.com/resources/blog/the-runaway-review/lithium-nickel-manganese-cobalt/</ref>.
====NMC====
====LFP====
LFP batteries have become highly utilized in EVs due to their high performance and thermal durability.

===Cans vs pouches===
The most common form factors for lithium cells are the can (i.e. 18650) or in soft metal-plastic pouches. It is easier to design a safe battery pack with cylindrical cells as each cells are protected in a hard shell that protects them from accidental perforation. Cylindrical cells tend to offer higher energy density, while pouches tend to offer higher power density. Cylindrical cells can be spot welded together with fairly inexpensive equipment, while pouches can be connected together by ultrasonic welding, laser welding, or mechanical assembly (rivets, nuts & bolts, ...). While cylindrical cells are typically found in small capacities ( < 4 Ah ), pouches can be found in high capacities ( > 10 Ah), greatly reducing the complexity of assembly of a battery pack, since fewer cells are required to meet the battery pack energy requirement.
====Pouches====
Pouches offer better heat dissipation than other type of cells, but their flexible and thin envelope make them prone to perforation or crushing. Some pouches have tabs on the same edge, some, on opposite edges. Opposite edge tabs allow better heat dissipation, but make packaging more complex. They stack easily, using most of the available space. The cells edges are fragile: treat them with care. It is preferable to ask the cell manufacturer to have the edges taped. Most pouches will ignite in case of a nail penetration. One way to reduce the risk it would ignite is to improve the cooling of the cell. As an example, using sheets of metal between cells would spread the heat (and evacuate it out of the cell).

Pouch cells can come in larger capacities than cylindrical cells. If the capacity is large enough you may not need any parallel cell connections at all.
====Cans====
Cans can be cylindrical or prismatic. They are typically safer than pouches, since they are are valve regulated and benefits from a hard shell, reducing their perforation and crushing risk. However, it is generally harder to cool them down. Cylindrical cans also have a lower packing factor than prismatic cells leading to an effectively reduced volumetric density. However, the process of cylindrical cell fabrication is so well honed that battery packs made with state of the art cylindrical cans compare in terms of metrics with battery packs made with state of the art pouches. Cans usually also contain a positive thermal coefficient (PTC) resistor that can protect the cell in case of a short circuit. However, this protection is usually not rated for high voltage packs, can could actually ignite a fire, in a high voltage pack. Cans also can ignite when perforated. Wrapping cells with a phase change material (PCM) is one of the solutions that have been developed to absorb heat in a thermal event, reducing the odds to create a cascade event.

===Cells capacity vs safety===
At the cell level, a smaller capacity cell is safer than a higher capacity cell: a small capacity cell may not store enough energy to generate a thermal runaway. However, it is false to assume that a huge capacity pouch is more dangerous than a couple of low capacity cells put in parallel. High capacity cells are made under extremely high quality control, while low capacity 18650s are not: it's more cash efficient to discard under performing these cells. Discarding a 240 Ah cell would be extremely costly for a manufacturer. Also, high capacity cells include various safety techniques (including internal self fusing) which intent is to prevent a problematic layer of the cell to make the cell enter a thermal runway.
==Arrangement of cells==
Cells can either be connected in series (positive to negative) or parallel (positive to positive, negative to negative). Connecting cells in series raises the pack voltage, and connecting them in parallel increases the energy capacity. So if you have two 3.6V 3Ah cells, connecting them in series gets you a 7.2V 3Ah battery pack. Connecting them in parallel gets you a 3.6V 6Ah battery pack.

The cell arrangement is often labeled as "''n''S''m''P", where ''n'' is the number of cells in series and ''m'' is the number of cells in parallel. So a pack with 50 cells in series and 8 cells in parallel would be 50S8P. Multiplying ''n'' and ''m'' gives you the total number of cells in the battery pack.

Your maximum tractive system voltage will set how many cells in series you use, and you need enough energy capacity to make it through the endurance event. This is where simulations can help you decide how big of a pack you need.

===Higher voltage, or higher current?===
Simulations can tell you how many Wh your accumulator needs, which tells you how many cells you need. What the simulation can't tell you is whether to put more cells in series or more in parallel. A 6 kWh pack could be 600V and 10Ah, or it could be 60V and 100Ah. A higher voltage will also mean lower current (a 60kW draw at 600V is 100A, but at 60V it's 1000A).

====Higher voltage/lower current pack====
Pros:
* Lower current means smaller wires, less I²R heat losses.
* Smaller wires mean less weight, smaller wire bend radius
Cons:
* BMS needs to monitor more voltages
* Higher voltage means a bigger spark gap, so less safe
* Higher voltages are harder to find parts for
====Lower voltage/higher current pack====
Pros:
* Smaller BMS
* Parts rated to lower voltages can be easier to find
* Lower voltages are theoretically safer
Cons:
* Tractive system conductors (wires, etc) get bigger with the square of current (because of I²R heat losses)
* Bigger wires mean more weight and bigger bend radius

====Other possible constraints====
* The rules (max segment voltage, max segment Joules)
* Motor controller selection
* Motor selection
* Other misc. component selection (AIRs, DC-DC converter, etc.)
* Packaging constraints
* Any legacy designs from your team
* University safety policies

==Packaging==
[[File:ParapostWC.png|right|middle|thumb|Pouch Cell Module Design Example. Credits: Poly eRacing 2014 (Polytechnique Montreal)]][[File:BP.PNG|right|middle|thumb|Cylindrical Cell Battery Pack Design Example. Credits: Poly eRacing 2016 (Polytechnique Montreal)]]
A battery pack has to be designed to resists the mechanical loads and impacts it will be subjected to and the thermal conditions it may be exposed in case of a thermal runaway. Also, it must be designed considering electrical safety in mind.

Requirements may differ according to the cell type choice. Pouch cells use a thin flexible shell, which may easily by punctured. Hence, it requires an additional protection and more professional fabrication processes to protect it from being scratched, punctured, teared. Cylindrical and prismatic cells, on the other side, encapsulate the active materials in a hard shell. However, if the shell is made of a conductive material, it may require a dielectric barrier to avoid a short circuit when cells are packaged in series.
===Mechanical loads===
The battery pack must resists to impacts and vibration. Bolts need to have positive locking mechanism. The battery pack should be built strong enough in a way that cells are not crushed in case of a drop on one of its corners.
===Thermal loads===
Lithium-ion cells don't like heat. As per the rules, cells exterior casing shouldn't reach 60 Celsius. Although it's easy to circumvent the rules here, no one should do it. The heat sources may be external such as the motors, inverters, solar load, etc. or internal from heat generated by the module's internal resistance.

The internal resistances of the modules can come from the bus bars, fusing, contactors, or other power distribution components. Most likely, the largest source of internal heat generation will come from the internal resistance of the cells (DCIR). DCIR is dependent on temperature, state of health, state of charge, and discharge time <ref> https://www.batterydesign.net/battery-cell/dcir-of-a-cell/ </ref>

===Safety===
Sharp edges inside the battery pack should be avoided. Appropriate clearance between wires should be maintained. Ensure that large voltage differences are far from each other. Positive locking mechanisms should ensure that screws don't loosen. It should be impossible to create a short circuit in case of the drop of tools. Think what could go wrong in case of an accident, and try to prevent it.
====Materials====
Dielectric materials and adhesives shall be fire retardant rated and be able to sustain to high temperatures.
====Grounding====
Conductive materials in the battery pack shall be grounded.
====Segregation====
As per the rules, modules need a fire retardant confinement to avoid a fire propagation within the battery pack.
===Interconnection===
Several techniques allow the cells interconnection. They are divided in two categories: the usage of mechanical fasteners and the usage of welding.
====Fasteners====
The concept behind the usage of [[Threaded_Fasteners|fasteners]] is to compress the current tabs together. In this kind of joint, conduction increases with area and with pressure. Hence, the goal is to apply a load as uniform as possible on an area as big as possible.
=====Grease=====
With time, the interface resistance can increase, due to oxidation. One can slow down the oxidation rate with the usage of grease. Grease is actually non conductive but as little impact on overall conduction as it is squished away by the pressure. Some greases contains conductive particles in order to improve their conductivity. Examples are De-Ox or Penetrox.
====Ultrasonic welding====
Ultrasonic welding is one of the best available techniques to join different materials (as found in lithium cells). It's the recommended technique for pouch cells. However, this type of welding equipment is expensive.
====Spot welding (also known as resistance welding)====
Resistance welding is speedy and low cost. It doesn't transfer a lot of heat to cell and welding quality is good.However, conductive materials (aluminum, copper, ...) require more power to weld than resistive materials(nickel, ...). It's the recommended technique for cylindrical cells.
====Brazing or Soldering====
Brazing and soldering are generally not recommended, because the heat required to melt the brazing alloy can damage the cells components. They can also result in brittle connections that are prone to failure.

====Crimping====
Crimping cell terminal is rare but can be done with extremely simple tools.

==Possible causes of a thermal runway==
Thermal runway (i.e. battery fire) can be caused by an internal short that would be due to a poor cell design and manufacturing quality control. However, it is more likely that it is due to abuse conditions.
===Abuse conditions===

* Charging when too cold
* Charging when too hot
* Discharging when too hot
* Storage at elevated temperature
* Internal damage due to high heat when interconnecting (by soldering)
* Overcharge
* Overdischarge or charging an overdischarged cell
* Overcurrent
* Crush
* Impact or drop
* Nail penetration
* Sharp chips / dust
* Leakage current

==What to do in case of a battery fire==
===Toxicity===
Lithium batteries are toxic. Especially their electrolyte, which is flammable and contains poison salts.
===What should I do?===
In case of a fire, ensure that nobody is in danger of breathing in the smoke. If nobody is in danger, sound the fire alarm and get away. If somebody is in danger, try to save them as fast as possible so you won't get hurt yourself, as people are more important that objects. Lithium caused fires are not easy to put out, even for people that know how. Smother the fire with Sand. ABC extinguishers will not do much except give the cause the fire to slow. If it starts within your car, don't think that you can save it, as its outcome is not good after it starts. Better yet, don't let batteries you own ever get to the point of causing a fire. This is the idea when using Lithium, you must prevent the batteries from getting to that point. too much voltage or too little voltage, too much current running through, or the temperature reaching too high, each have particularly nasty consequences. For any person using lithium batteries, it is wise to read up on this technology before using, so that one can become aware of the challenges of putting out a fire caused by lithium-cell batteries.

==How to properly use a battery pack==
[[Category:Electric Vehicle]]

The proper usage of the battery shall be limited by the battery management system (BMS). Here's a list of advice:
* As per the rules, avoid exceeding 60 Celsius degree.
* Do not overcharge the cells (generally over 4.2V each), nor over discharge the cells(generally under 2.7V each).
* As per the rules, ensure that the battery pack design does not allow the drop of tools to create a short circuit.
* Ensure that all conductive materials in the battery pack is grounded.
* Ensure that all materials of the battery pack are fire retardant.
The proper storage of the battery shall be:
* In a fireproof container.
* At room temperature or cooler (< 25 Celsius degree).
* In a stable position.
* In a well ventilated area.
=References=
<references />

Battery pack

2024-04-05T13:45:59Z

SpookySimon: /* Chemistry */ chemistry intro

The '''battery pack''' contains the electrical potential energy used by the [[:Category:Electric_Vehicle|traction system]] and [[:Category:Electronics|onboard electronics]]. The battery pack is often referred to in industry as the rechargeable energy storage system or RESS.
==Introduction==

==Goals==
Safety & reliability should rank pretty high in design criteria as it's impossible to win a competition with a car who caught fire.


===Performance Goals===
The battery pack capacity should be sufficient to complete the desired driving cycle, frequently this is based on the endurance circuit at competition or the expected cumulative drive cycle over the course of a test day.

The battery pack should be capable of safely discharging at the commanded current rate, both peak and continuous.

The highest rate of charge is often in regenerative braking. The pack should be designed to safely accommodate the peak and continuous charge rates from regen braking.
===Design Goals===
The pack may be required to meet other goals such as packaging requirements, mass, cost, material specification, etc. These can preclude meeting design goals, particularly capacity. Correctly prioritizing team and system goals will be critical in making these compromises.
==Cell selection==
The selection process of a lithium-ion/lithium-polymer cell is highly dependent on the application. Before even starting battery pack design, it is crucial to understand the operating conditions. A light-weight car with 2WD requires less power than a heavy 4WD car with a full aero package. Because there is a trade-off between cell energy density (Wh/kg) and cell power density (W/kg), it is then possible to compare the performance of cell chemistries using lap simulation: there are cases where a higher specific energy cell is optimal, and others where high specific power is.
===Chemistry===
Most batteries used in EVs will have a lithium based chemistry. The two main lithium chemistries are nickel manganese cobalt oxides (NMC) or lithium iron phosphate (LFP). NMC batteries are an older technology, and are more common and cheaper in most configurations. While cobalt is not legally defined as a "conflict mineral", the extraction is closely tied to human suffering<ref>Dasilva, Jeremy. Conflict Implications of Rising Cobalt Demand and the Effects of Classifying Cobalt as a Conflict Mineral on the DRC. 2022. Johns Hopkins, Masters Thesis. JScholarship Library https://jscholarship.library.jhu.edu/server/api/core/bitstreams/b2780da6-5830-4b07-8a23-a5d09051b9f5/content</ref>. This alongside the relative rarity of the element has lead to a push for non-cobalt battery chemistries<ref>https://www.mitsubishicritical.com/resources/blog/the-runaway-review/lithium-nickel-manganese-cobalt/</ref>.
====NMC====
====LFP====

===Cans vs pouches===
The most common form factors for lithium cells are the can (i.e. 18650) or in soft metal-plastic pouches. It is easier to design a safe battery pack with cylindrical cells as each cells are protected in a hard shell that protects them from accidental perforation. Cylindrical cells tend to offer higher energy density, while pouches tend to offer higher power density. Cylindrical cells can be spot welded together with fairly inexpensive equipment, while pouches can be connected together by ultrasonic welding, laser welding, or mechanical assembly (rivets, nuts & bolts, ...). While cylindrical cells are typically found in small capacities ( < 4 Ah ), pouches can be found in high capacities ( > 10 Ah), greatly reducing the complexity of assembly of a battery pack, since fewer cells are required to meet the battery pack energy requirement.
====Pouches====
Pouches offer better heat dissipation than other type of cells, but their flexible and thin envelope make them prone to perforation or crushing. Some pouches have tabs on the same edge, some, on opposite edges. Opposite edge tabs allow better heat dissipation, but make packaging more complex. They stack easily, using most of the available space. The cells edges are fragile: treat them with care. It is preferable to ask the cell manufacturer to have the edges taped. Most pouches will ignite in case of a nail penetration. One way to reduce the risk it would ignite is to improve the cooling of the cell. As an example, using sheets of metal between cells would spread the heat (and evacuate it out of the cell).

Pouch cells can come in larger capacities than cylindrical cells. If the capacity is large enough you may not need any parallel cell connections at all.
====Cans====
Cans can be cylindrical or prismatic. They are typically safer than pouches, since they are are valve regulated and benefits from a hard shell, reducing their perforation and crushing risk. However, it is generally harder to cool them down. Cylindrical cans also have a lower packing factor than prismatic cells leading to an effectively reduced volumetric density. However, the process of cylindrical cell fabrication is so well honed that battery packs made with state of the art cylindrical cans compare in terms of metrics with battery packs made with state of the art pouches. Cans usually also contain a positive thermal coefficient (PTC) resistor that can protect the cell in case of a short circuit. However, this protection is usually not rated for high voltage packs, can could actually ignite a fire, in a high voltage pack. Cans also can ignite when perforated. Wrapping cells with a phase change material (PCM) is one of the solutions that have been developed to absorb heat in a thermal event, reducing the odds to create a cascade event.

===Cells capacity vs safety===
At the cell level, a smaller capacity cell is safer than a higher capacity cell: a small capacity cell may not store enough energy to generate a thermal runaway. However, it is false to assume that a huge capacity pouch is more dangerous than a couple of low capacity cells put in parallel. High capacity cells are made under extremely high quality control, while low capacity 18650s are not: it's more cash efficient to discard under performing these cells. Discarding a 240 Ah cell would be extremely costly for a manufacturer. Also, high capacity cells include various safety techniques (including internal self fusing) which intent is to prevent a problematic layer of the cell to make the cell enter a thermal runway.
==Arrangement of cells==
Cells can either be connected in series (positive to negative) or parallel (positive to positive, negative to negative). Connecting cells in series raises the pack voltage, and connecting them in parallel increases the energy capacity. So if you have two 3.6V 3Ah cells, connecting them in series gets you a 7.2V 3Ah battery pack. Connecting them in parallel gets you a 3.6V 6Ah battery pack.

The cell arrangement is often labeled as "''n''S''m''P", where ''n'' is the number of cells in series and ''m'' is the number of cells in parallel. So a pack with 50 cells in series and 8 cells in parallel would be 50S8P. Multiplying ''n'' and ''m'' gives you the total number of cells in the battery pack.

Your maximum tractive system voltage will set how many cells in series you use, and you need enough energy capacity to make it through the endurance event. This is where simulations can help you decide how big of a pack you need.

===Higher voltage, or higher current?===
Simulations can tell you how many Wh your accumulator needs, which tells you how many cells you need. What the simulation can't tell you is whether to put more cells in series or more in parallel. A 6 kWh pack could be 600V and 10Ah, or it could be 60V and 100Ah. A higher voltage will also mean lower current (a 60kW draw at 600V is 100A, but at 60V it's 1000A).

====Higher voltage/lower current pack====
Pros:
* Lower current means smaller wires, less I²R heat losses.
* Smaller wires mean less weight, smaller wire bend radius
Cons:
* BMS needs to monitor more voltages
* Higher voltage means a bigger spark gap, so less safe
* Higher voltages are harder to find parts for
====Lower voltage/higher current pack====
Pros:
* Smaller BMS
* Parts rated to lower voltages can be easier to find
* Lower voltages are theoretically safer
Cons:
* Tractive system conductors (wires, etc) get bigger with the square of current (because of I²R heat losses)
* Bigger wires mean more weight and bigger bend radius

====Other possible constraints====
* The rules (max segment voltage, max segment Joules)
* Motor controller selection
* Motor selection
* Other misc. component selection (AIRs, DC-DC converter, etc.)
* Packaging constraints
* Any legacy designs from your team
* University safety policies

==Packaging==
[[File:ParapostWC.png|right|middle|thumb|Pouch Cell Module Design Example. Credits: Poly eRacing 2014 (Polytechnique Montreal)]][[File:BP.PNG|right|middle|thumb|Cylindrical Cell Battery Pack Design Example. Credits: Poly eRacing 2016 (Polytechnique Montreal)]]
A battery pack has to be designed to resists the mechanical loads and impacts it will be subjected to and the thermal conditions it may be exposed in case of a thermal runaway. Also, it must be designed considering electrical safety in mind.

Requirements may differ according to the cell type choice. Pouch cells use a thin flexible shell, which may easily by punctured. Hence, it requires an additional protection and more professional fabrication processes to protect it from being scratched, punctured, teared. Cylindrical and prismatic cells, on the other side, encapsulate the active materials in a hard shell. However, if the shell is made of a conductive material, it may require a dielectric barrier to avoid a short circuit when cells are packaged in series.
===Mechanical loads===
The battery pack must resists to impacts and vibration. Bolts need to have positive locking mechanism. The battery pack should be built strong enough in a way that cells are not crushed in case of a drop on one of its corners.
===Thermal loads===
Lithium-ion cells don't like heat. As per the rules, cells exterior casing shouldn't reach 60 Celsius. Although it's easy to circumvent the rules here, no one should do it. The heat sources may be external such as the motors, inverters, solar load, etc. or internal from heat generated by the module's internal resistance.

The internal resistances of the modules can come from the bus bars, fusing, contactors, or other power distribution components. Most likely, the largest source of internal heat generation will come from the internal resistance of the cells (DCIR). DCIR is dependent on temperature, state of health, state of charge, and discharge time <ref> https://www.batterydesign.net/battery-cell/dcir-of-a-cell/ </ref>

===Safety===
Sharp edges inside the battery pack should be avoided. Appropriate clearance between wires should be maintained. Ensure that large voltage differences are far from each other. Positive locking mechanisms should ensure that screws don't loosen. It should be impossible to create a short circuit in case of the drop of tools. Think what could go wrong in case of an accident, and try to prevent it.
====Materials====
Dielectric materials and adhesives shall be fire retardant rated and be able to sustain to high temperatures.
====Grounding====
Conductive materials in the battery pack shall be grounded.
====Segregation====
As per the rules, modules need a fire retardant confinement to avoid a fire propagation within the battery pack.
===Interconnection===
Several techniques allow the cells interconnection. They are divided in two categories: the usage of mechanical fasteners and the usage of welding.
====Fasteners====
The concept behind the usage of [[Threaded_Fasteners|fasteners]] is to compress the current tabs together. In this kind of joint, conduction increases with area and with pressure. Hence, the goal is to apply a load as uniform as possible on an area as big as possible.
=====Grease=====
With time, the interface resistance can increase, due to oxidation. One can slow down the oxidation rate with the usage of grease. Grease is actually non conductive but as little impact on overall conduction as it is squished away by the pressure. Some greases contains conductive particles in order to improve their conductivity. Examples are De-Ox or Penetrox.
====Ultrasonic welding====
Ultrasonic welding is one of the best available techniques to join different materials (as found in lithium cells). It's the recommended technique for pouch cells. However, this type of welding equipment is expensive.
====Spot welding (also known as resistance welding)====
Resistance welding is speedy and low cost. It doesn't transfer a lot of heat to cell and welding quality is good.However, conductive materials (aluminum, copper, ...) require more power to weld than resistive materials(nickel, ...). It's the recommended technique for cylindrical cells.
====Brazing or Soldering====
Brazing and soldering are generally not recommended, because the heat required to melt the brazing alloy can damage the cells components. They can also result in brittle connections that are prone to failure.

====Crimping====
Crimping cell terminal is rare but can be done with extremely simple tools.

==Possible causes of a thermal runway==
Thermal runway (i.e. battery fire) can be caused by an internal short that would be due to a poor cell design and manufacturing quality control. However, it is more likely that it is due to abuse conditions.
===Abuse conditions===

* Charging when too cold
* Charging when too hot
* Discharging when too hot
* Storage at elevated temperature
* Internal damage due to high heat when interconnecting (by soldering)
* Overcharge
* Overdischarge or charging an overdischarged cell
* Overcurrent
* Crush
* Impact or drop
* Nail penetration
* Sharp chips / dust
* Leakage current

==What to do in case of a battery fire==
===Toxicity===
Lithium batteries are toxic. Especially their electrolyte, which is flammable and contains poison salts.
===What should I do?===
In case of a fire, ensure that nobody is in danger of breathing in the smoke. If nobody is in danger, sound the fire alarm and get away. If somebody is in danger, try to save them as fast as possible so you won't get hurt yourself, as people are more important that objects. Lithium caused fires are not easy to put out, even for people that know how. Smother the fire with Sand. ABC extinguishers will not do much except give the cause the fire to slow. If it starts within your car, don't think that you can save it, as its outcome is not good after it starts. Better yet, don't let batteries you own ever get to the point of causing a fire. This is the idea when using Lithium, you must prevent the batteries from getting to that point. too much voltage or too little voltage, too much current running through, or the temperature reaching too high, each have particularly nasty consequences. For any person using lithium batteries, it is wise to read up on this technology before using, so that one can become aware of the challenges of putting out a fire caused by lithium-cell batteries.

==How to properly use a battery pack==
[[Category:Electric Vehicle]]

The proper usage of the battery shall be limited by the battery management system (BMS). Here's a list of advice:
* As per the rules, avoid exceeding 60 Celsius degree.
* Do not overcharge the cells (generally over 4.2V each), nor over discharge the cells(generally under 2.7V each).
* As per the rules, ensure that the battery pack design does not allow the drop of tools to create a short circuit.
* Ensure that all conductive materials in the battery pack is grounded.
* Ensure that all materials of the battery pack are fire retardant.
The proper storage of the battery shall be:
* In a fireproof container.
* At room temperature or cooler (< 25 Celsius degree).
* In a stable position.
* In a well ventilated area.
=References=
<references />

Talk:Rivets

2024-04-05T13:15:21Z

SpookySimon: Talk page autocreated when first thread was posted

Thread:Talk:Rivets/maybe kill this page?

2024-04-05T13:15:20Z

SpookySimon: New thread: maybe kill this page?

Why do we have this page... adds very little, cant see any reason to have it on the fs wiki lol

Suspension Geometry and Kinematics

2024-04-05T13:11:28Z

SpookySimon: /* Track width */

==Track width==
This has 4 main considerations:
* If the track is too narrow, the car may fail the 60deg tilt test
** The minimum track width for a vehicle can be found with some trig and your vehicle's CG height
* Narrower track increases load transfer, reducing maximum potential lateral grip
* Narrower track reduces rear wing, front wing, and undertray width, reducing aero potential
* Narrower track tightens the racing line - can be very beneficial on a maneuverability emphasized course, such as the autocross and endurance. 
** Narrower generally makes a more compact car, that will at least in theory be lighter and have less yaw inertia
These need to be analyzed for an adequate tradeoff.

Track width is regulated in FSAE by rule '''V.1.3'''. Beyond the tilt test, if the vehicle has different track widths between front and rear, the smaller can be no less than 75% of the larger.

==Wheelbase==
Considerations:
* 1525mm minimum set by rules
* Shorter generally makes a more compact car, that will at least in theory be lighter and have less yaw inertia
* Shorter reduces steering angle requirement per a given corner radius, geometrically speaking
* Shorter makes the car less stable at high speeds, but the minimum set is well above any sort of safety concern
* Longer can allow more downforce, at least in theory, from undertray and side aero. But, is it worth the penalty?
* Longer can allow more flexibilty with CG longtitudonal location
An adequate compromise must be made.

==Camber==
[[File:Annotation 2020-05-25 001418.png|right|middle|thumb|Camber Justification ]]
Camber is the front view angle of the tire from the vertical axis. The top of the tire pointing inwards is referred to as "negative camber". Most cars in the automotive industry, motorsports and FS/FSAE have negative camber.



The tire's camber will change as the suspension articulates. The tire will also see camber change due to body roll seen in a turn. This is known, unsurprisingly, as ''Camber gain''. With 0 camber gain, a vehicle that rolls 1 degree will see 1 degree of camber change in the tire. On a double-wishbone car, there are two simple ways to achieve camber gain. The first is to make the upper a-arm shorter than the lower a-arm. The second is to place the inboard pickup points vertically closer than the outboard points are.


By making the upper a-arm shorter than the lower, and the inboard points closer together than the outboard, the wheel will gain negative camber with wheel travel canceling out part of the camber lost in roll. An easy way to quantify the camber gain is the Front-view swing arm length (FVSAL) - the line from the wheel center to the Instant Center (IC) of the 2 arms, found at the intersection of the extension of the arms line of action. This can allow for a simple sin/cosine relation for camber gain, although it is idealized since the FVSAL doesnt stay constant through the travel. For reference, the 2018 Ryerson car had a 45inch FVSAL, allowing it to run relatively minimal static camber.

Why would that be desirable? static camber could cause the inner part of the tire to overheat on the straights, and so even if the camber during a corner is ideal, the tire wear and tire temperature would say otherwise. So, general considerations in the solution:
* Minimize roll, to reduce the need for static camber. However, a stiffer car will be more upset by bumps, which is difficult to quantify.
* Use camber gain, but remember that in pitch camber gain will reduce the longitudonal grip (for longt, you want 0 camber)
* Account for camber deflection sources, and build in adjustabity of at least static camber.
The "ideal" compromise of these factors has requires detailed analysis.

As a note: positive camber is undesirable from a traction POV. Positive camber has the potential to improve drivability, as seen on 1950s F1 cars.

==Toe==
A minor adjustment. A stability fine tuning tool, to make the car feel better for the driver. Not a major performance item. Generally, toe out (front of wheels pointing outwards) is for response, and toe in is for stability. You would almost never see toe out on the rear, while the front is likely to be toe out.

However, that is within the usable range (-1:1deg?). Compliance that is often present, especially on the rear, can turn an otherwise decent car into an unpredictable deathtrap. Take into consideration:
* Toe base (mechanical advantage of the toe arm)
* Bolted joint tolerance
* Anything that is not axially loaded or not a direct line of action

As Claude Rouelle said:

“Nothing is rigid; 0.2mm of deflection here and 0.3mm of deflection there, and suddenly your front camber or you rear toe is far, far away from what you thought it was. From the driver input (steering wheel, brake pedal, throttle) to the tyres’ contact patch, there are dozens of non-linear springs, dampers, and hysteresis that compromise the racecar’s response to that driver input. [[Compliance]] is the biggest enemy of your driver’s Control and Confidence.”
==Kingpin==
Not that important for vehicle handling - Its main effect is on reducing scrub radius - but, scrub radius as well is less important on a racetrack with no major curbs/bumps where the steering wheel can be jerked around.

Kingpin adds a VERY minor self centering effect (can be usually neglected relative to caster, even at 10+ deg), and an also minor but not neglegible positive camber gain in steer. This is a symmetric effect left to right, but not once caster is taken into account.

However, to give an example, on a car with 4deg of caster and 8deg of kingpin, the negative camber gain from caster would overpower the kingpin by at least ~2-3x. There are equations to calculate this, but you can also set up your solidworks sketches correctly, and observe the effect in the sketches (if they are made movable), or in the assembly.

==Caster==
[[File:Image161.png|right|middle|thumb|Caster Offset ]]Caster is the side-view angle of the steering axis to the vertical. It affects:
* Mechanical trail
** Steering effort
** "sense of direction the wheels want to go to" - i.e, where would the wheels steer if you let go of the steering wheel
** High speed stability 
* Jacking
** Low speed oversteer inducing, as a tuning mechanism
** Another variable in steering effort
** Consider it as adding roll also!
* Steer camber
** Negative camber on outside wheel, positive on inner - both good!
*** But, do you want more camber for a tight hairpin than for a wide sweeper? I dont think so! in practice, this can be neglegible if caster is low enough, but it is a factor.

Remember, you can have "Caster offset", to independently affect mechanical trail (the most important one) from the other 2.

Also, you dont want to drown out the pneumatic trail with too much mechanical trail. Youll just end up with super heavy steering all the time, instead of giving the driver a signal of understeer like the pneumatic trail should.

==Roll Center==
==Bump Center==
==CAD Tips==
Its helpful to set the CAD up for easy adjustment.

That can be done by:
* Integrating the suspension geometry sketches into the frame file
* Having a few levels of sketches, set up for ease of parameter adjustment:
** A 2D "geometry sketch", that isnt movable, and has all the critical angles and dimensions set, as well as static roll center visible with driven dimensions
** A 3D "geometry sketch", adding in caster
** A 3D "linkage sketch" - movable, with equal length relations to the "geometry sketch" - so that it can be cycled through travel, while getting geometry updates from the geometry sketch.
It can look like this:

[[File:Image162.png|center|middle|thumb|Movable Sketch ]]

These sketches would then have in-context relations to the bellcrank, a-arms, uprights etc to have their geometry update accordingly to geometry sketch changes.

[[Category:Suspension]][[Category:Vehicle Dynamics]]

Locking Adhesive

2024-04-02T18:18:26Z

SpookySimon:

'''Locking adhesive''', frequently known by the genericized brand Loctite is used to stop [[Threaded Fasteners|threaded fasteners]] from coming undone.

In FSAE, locking adhesive, no matter how applied, is not considered positive locking and cannot be relied on as the only locking mechanism for critical fasteners.

Locking Adhesive

2024-04-02T18:14:53Z

SpookySimon: filling this out probably as much as we need. could add application notes or links.

Locking adhesive, frequently known by the genericized brand Loctite is used to stop [[Threaded Fasteners|threaded fasteners]] from coming undone.

In FSAE, locking adhesive, no matter how applied, is not considered positive locking and cannot be relied on as the only locking mechanism for critical fasteners.

Sandwich Panel

2024-04-02T18:09:48Z

SpookySimon: adding further reading links that go to really in depth wikipedia articles.

Panel (generally composite) that is made of core middle sandwiched between sheets of material. Structural composites on the car are almost always of this construction type.

Wikipedia articles for further reading:
* https://en.wikipedia.org/wiki/Sandwich-structured_composite
* https://en.wikipedia.org/wiki/Sandwich_theory

<!-- maybe add some references to more academic references>

[[Category:Materials]]

System Simulation

2024-04-02T14:24:04Z

SpookySimon: /* Engine Control */

used to tune.
=Intake=
=Drivetrain=
=Engine Control=

=Multi-Component Model=
[[Category:Internal Combustion]]

System Simulation

2024-04-02T14:11:52Z

SpookySimon: proposed outline

used to tune.
=Intake=
=Drivetrain=
=Engine Control=

[[Intake]][[Drivetrain]] - fdr, gearing[[Engine Control]]
=Multi-Component Model=
[[Category:Internal Combustion]]

Master Cylinders

2024-04-02T14:07:54Z

SpookySimon: proposed outline in NOTES

<!-- Proposed outline:

brief intro
=sizing=
=packaging=
=bleeding=
=troubleshooting=
=references=
>
[[Category:Brakes]]

Steering Wheel

2024-04-02T14:05:24Z

SpookySimon: proposed outline in NOTES

<!-- Proposed Outline:

brief intro
=rules=
=common construction methods=
=DAQ display / Electronics=
=References=
>

[[Category:Ergonomics]]

Steering Wheel

2024-04-02T14:05:09Z

SpookySimon: proposed outline in NOTES

<!-- Proposed Outline:

brief intro
=rules=
=common construction methods=
=DAQ display / Electronics=
=References=

[[Category:Ergonomics]]

Epoxy

2024-04-02T14:01:21Z

SpookySimon: proposed outline in NOTES

<!-- NOTE: This should be a FORMULA SAE / FORMULA STUDENT *SPECIFIC* page, this is not wikipedia>
<!-- Proposed Outline:

Brief intro
=Use in composites=
==Cure time==
==Use methods, advice==
==Safety==
===exothermic reaction===
===Skin Irritation===
=Non-composite Uses=
=References=
>

[[Category:Materials]]

Cooling

2024-04-02T13:48:58Z

SpookySimon: /* Simulation/Analysis */

A '''cooling''' system is needed to keep the [[Engine|engine]] or motors within their operational temperature range.

Of all chemical energy burned in the engine, the largest fraction of the energy goes into heating the engine and the exhaust<ref name=heywood>Heywood, John B. "Chapter 12: Engine Heat Transfer" Internal Combustion Engine Fundamentals, McGraw-Hill, 1988, pp. 668-711.</ref><ref>http://web.mit.edu/2.61/www/Lecture%20notes/Lec.%2018%20Heat%20transf.pdf slides 3,4 are taken from Heywood textbook if you don't have a copy</ref>. Please refer to chapter 12 of the textbook ''Internal Combustion Engine Fundamentals'' by Heywood for reference and detailed information on engine specific heat transfer, this page will be kept as a FSAE specific reference page.

EV Cooling follows much of the same principals with the total heat rejection on a smaller scale, however there is generally no OEM radiator to compare to. Additionally, EVs have the option to use oil as a cooling liquid instead of water.
=Theory=
Cooling systems are designed to dissipate the unwanted thermal energy. Systems are often designed around heat exchangers (HEXs), allowing for efficient exchange of heat from a hot fluid to a cooler one. There are three main methods of heat transfer;
* Conduction: Heat transfer over a temperature differential without motion between the materials
* Convection: Heat transfer over a temperature differential with fluid motion between the materials
* Radiation: Heat transfer in the form of electromagnetic radiation absorbed and emitted by bodies
A heat exchanger (HEX) is normally designed to facilitate the heat transfer between two fluids using conduction and convection. The most common HEX in FSAE/FS is a water to air cooler, meaning it transfers heat between the hot water and the cooler air. These HEXs have a few distinct characteristics, full metal construction, thin metal fins in the streamwise direction, water inlets on top and bottom, with air inlets on the front and back. The metal construction is advantageous because of its high conductive heat transfer coefficient and its low specific heat. These factors allow the metal rapidly conduct heat from the hotter internal water channels to the cooler metal fin tips. Aluminum is nearly universally used in automotive radiators. While materials such as copper may notionally provide more cooling due to higher thermal conductivity, the thermal resistance of aluminum sheet metal is so low that the heat transfer from the water circuit to the air is limited by the convective coefficients. Aluminum also is light and strong as fins or sheets. The fin structure is to maximize convection heat transfer by increasing the surface area the air flows over. The convection heat transfer coefficient is also a function of the airspeed passing the fin, allowing for 'forced convection' where a fan and or vehicle speed is used to impart an inlet speed to the system. Radiator performance varies widely based upon water channel sizes, fin spacing, and a plethora of other characteristics.

For a more detailed understanding of theory, any heat transfer textbook such as ''Incropera and Dewitt ''will serve. ''Kays and London'''s heat exchanger text is invaluable as a practical reference. It includes heat transfer coefficients for various fin and tube geometries. A car radiator is considered a cross-flow radiator with both fluids unmixed. It is possible to measure the geometry of your radiator's fins, determine what type of fin geometry you are using, and then look up the appropriate set of coefficients for a rather robust heat exchanger model.

=System Design=
The amount of thermal power that the engine puts into the water has to be the same as the thermal power the radiator dissipates ''at steady state''. FSAE rules state that the system must be cooled using water only(IC and EV) or oil(EV). The coolant can not contain additives. Additionally the system must be able to pass a 45 degree tilt test with no leaks.

There are a couple of things that influence how much power the cooling system has. Because the heat generation is not a tunable parameter in the cooling system design, the parameters that can be easily adjusted are:
* Radiator Choice (Type, Size, Number)
* Radiator Packaging
* Radiator Angle
* Radiator Ducting
* Fan Sizing
* Fan Control

==Cooling Power Determination==
===Combustion===
A rule of thumb is 1/3 of the power you put into the engine in the form of fuel flow turns into heat. 1/3 becomes the power that turns the wheels and the last third comes out as exhaust enthalpy. This ratio means that the power the radiator has to dissipate is approximately the same as the power sent to the wheels. The actual cooling load can range between 60 percent to 20 percent of the fuel LHV depending on the engine and driving conditions: a throttled engine will be much less thermally efficient<ref name = heywood/>.

Keep in mind though that you don't drive full throttle all the time, so you should verify any cooling assumptions made during design with physical tests.

Finding average power output of the engine is one way to determine an approximate necessary cooling power for the engine. This can be accomplished by measuring fuel consumption or engine torque/vehicle velocity (P = FxV).
===EV===
The main heat generating components are the motor and motor controller. Conservative rules of thumb put the ballpark efficiencies at about 90% for both components. The heat generated by this powertrain would be about 15 kW<ref>According to the equation Q = Pelectric,input*(1 - ηcontroller * ηmotor) = 80*(1-0.9*0.9) = 15.2. Some papers use Q = Pelectric,input*[(1 - ηcontroller) + ηcontroller * (1 - ηmotor)] which is numerically equivalent</ref> when running at max power. A better estimate is 30kW average draw for the traction system<ref>Chiu, Harriet A. ''Design of a FSAE Cooling System''. 2019. MIT </ref> which yields a ballpark heat generation of ~6kW. This is likely higher than most teams will see.

A more thorough method is to use data from previous years, or that generated by a [[Introduction to VD Simulation | lap sim]], coupled with the efficiencies given on the motor/motor controller datasheets if available to model the generation over a lap<ref>LaMarre, Jeff. "FSAE Electric Vehicle Cooling System Design". 2015. UAkron</ref>.

EV teams also need to consider cooling the [[Battery_pack | battery]]. This is generally best considered as a battery design problem, as it requires a different approach to that of the motor.

==Radiator Choice==
The radiator for most teams is outside of the scope of custom design and production. Therefore, many teams have limited to no ability to tune radiator parameters, and the choice of which radiator to run becomes the main design choice. Radiator selection can be done by size: length, width, and thickness. Radiator dimensions are not created equal as lower temperature water will be cooled less than high temperature water. The focus should be on getting more mass flow of hot water. On a downflow radiator, this means radiator width will often be more impactful than radiator length. A longer radiator forces water to travel further through the radiator, causing a greater ΔT between the inlet and outlet, and a lower average water temperature. The width of a radiator is analogous to the diameter of a pipe, the larger the width, the more water can flow through the radiator at a time. The thickness of the radiator will increase the massflow of the water through the radiator and the amount of time a quantity of air is in contact with the radiator, but can negatively impact the massflow of air through the radiator.

The two types of radiator are cross flow and down flow. The difference in performance is insignificant. A downflow radiator has water enter the top and go to the bottom in one pass. Crossflow radiators force water through the radiator sideways and can include multiple passes. Downflow radiators are most common in FSAE as they are usually taller and skinnier and will fit on the side of the vehicle without increasing frontal cross sectional area.

Fin density is an important part of radiator design, but is not tunable, and not worth the time to specify if buying an off-the-shelf solution.

You can also purchase radiators by specifying the approximate engine power or by contacting a radiator supplier for assistance.

==Radiator Placement==
'''Side''' The most common radiator placement in FSAE is on the side of the vehicle, usually within the sidepod. This is a space that is usually free of other systems, somewhat unobstructed airflow, and for most bike engines it is a favorable routing position.

The sidepod design allows the team to guide air into the radiator. A properly constructed duct will dramatically increase cooling power and can reduce drag.

'''Rear''' A few teams rear-mount the radiator. Rear mounting is usually to take advantage of diffuser airflow, free up space on the side for aero devices, or to tune weight distribution. The disadvantages can be the reduced free air flow, yaw inertia, and possible routing complications.


'''Multiple''' 
Common FS/FSAE electric mounting scheme is to run two symmetric radiators<ref>https://www.instagram.com/p/B8jcYNqhux2/?igshid=1hwa03kwfnw3</ref>.
==Fluid Flow Rates==
Tuning radiator performance is largely balancing the flow rates of the water and the air passing through the radiator. For analysis, heat exchangers use a term called capacity rate which is the mass flow rate times the specific heat of the fluid. An over-simplified way to think about this is as if the fluid are conveyer belts for "heat units", the specific heat capacity is how many "heat units" can fit on the belt at a time and the mass flow rate is how fast the belt is going. Heat capacity rate is defined as:
: C = ṁ * cp

The maximum possible heat transfer by a heat exchanger will be limited by the smallest heat capacity rate as seen by the equation:
: Qmax = Cmin * (thot,inlet - tcold,inlet)

The limiting factor in our analogy will be whichever conveyer belt is filled up first. The ratio of flow rates is called Capacity-Rate Ratio and is the lower flow rate Cmin over Cmax. The effectiveness of the heat exchanger will be a function of this ratio. A few assumptions will be important in the flow rate discussion here: (1) The engine is designed such that the water inlet temperature to the radiator (thot,inlet) will be the same temperature regardless of the water flow rate and (2) The inlet air temperature will be independent of the air flow rate.
The above equation tells us two things: heat transfer is limited by one of the mass flow rates, and that increasing the lowest heat capacity rate will increase our heat transfer rate.
We can discuss the impact of changes to a single fluid flow rate interchangeably with capacity rate if we assume the heat capacity of the fluid stays constant, but not when comparing the capacity rates of two fluids.
===Water===
Tuning water mass flow rate is about finding the right balance: if you have 0 water flow rate, you'll get close to 0 cooling no matter what else you do. Hot water will stay in the engine, cold water will stay in the radiator. On the other end, there is a practical limit of flow rate due to pressure rating of the radiator and pump specifications. Between the extremes, an increase in water flow rate will increase heat transfer until it is no longer the limiting factor. If you have a properly sized water pump and swap to a bigger one, you'll see limited gains.

Practically speaking: Upgrading a water pump can be a serious investment in time and resources. The water pumps on the stock engine are designed to pump coolant for an unrestricted engine running at significantly higher power for long periods of time specifically on sport bikes like the YZ450 or CBR600RR. Therefore, it is unlikely but certainly possible that upgrading the water pump is a good step for your team.

Note: The stock CBR 600RR water pump generates 30-60 Lpm<ref>https://www.facebook.com/photo/?fbid=10150829256503036&set=a.10150813204983036</ref>. With a few assumptions, we can calculate the maximum ballpark capacity rate for a CBR:
* Volumetric flow rate of 60 LPM
* 1kg/L density of water
* Temp near 100C<ref>cp of water is slightly temperature dependent at these temps. The higher the inlet water temp of the hot fluid, the higher the max heat transfer rate. We cannot use a higher temperature for FSAE coolant than 100C without cheating.</ref>
* cp of 4.2157 KJ/kg*k
This yields a maximum heat capacity rate of 4.2157 kW/k

===Air===
The specific heat capacity (cp) of air is 1.006 between 0 and 35C<ref> It also only increases to 1.007 even past 45C so I think it's more than fair to assume constant for use in FSAE analysis https://www.engineeringtoolbox.com/air-specific-heat-capacity-d_705.html</ref> so you'll need about 4 times the mass flow rate of air to reach heat capacity rate parity with water, or, assuming ~1.2g/L density of air, more than 3300 times the volumetric flow rate to reach parity.

Sufficient air flow for adequate cooling is easy to achieve, but making a simple mistake that costs cooling performance is equally easy. The first decision that will affect the radiator performance is location of the radiator, this will dictate how much clean air the radiator will see during driving operation. If packaged behind the car, it is possible that the radiator will see increased air temperature because of the engine. The main ways the team can achieve adequate airflow once the radiator has been located on the vehicle are angling the radiator, utilizing fans, and adding a duct or shroud.

'''Angle of radiator''' Angling a radiator will allow a larger radiator area to fit in a similar frontal cross sectional area, effectively fitting a larger radiator in the same space. Yes, this will sacrifice fore/aft space, but this space should be free of obstruction anyways in order to allow for free air-flow. You can angle it to about 45° relative to the airflow both vertically and horizontally without any significant loss in cooling power<ref>Fenske, Jason. "Formula One Radiator Technique - Explained". https://www.youtube.com/watch?v=l3SJlGqc0P0</ref>. Tilting it in the vertical and one of the horizontal axes will allow a radiator of ''double'' surface area in the same frontal area, or to halve the frontal area with the same radiator.

'''Fans''' Because air capacity rate is likely to be a limiting factor, the vehicle will need a way to keep air flowing through the radiator when the vehicle is not moving. Fans attached to the back of the radiator are instrumental in vehicle operation. Fans should be sized for their airflow ratings, and attached such that all the air drawn by the fan is pulled through the radiator, this is done using a shroud. It may be necessary due to electrical draw constraints to only run the fans when needed. This can be accomplished by using the ECU to control a relay based on temperature or speed or by having the driver control them according to a light in the cockpit.

Because the margin between running temperature (about 90C) and disaster (100C) is so tight (check these numbers), the fans might have to run fairly aggressively especially on a hot day when chaining autocross laps. A tight seal between fan shroud and the radiator is key to avoid leakage. Spacing between the fan and radiator is also key: you want a uniform pressure difference across the radiator to achieve a uniform flow rate.

'''Ducting/Shrouding''' A shroud seals the fan to the radiator ensuring all of the air flow generated by the fan goes into raising the mass flow through the radiator. A duct channels air from the environment through the radiator and back to the environment. A properly designed duct can produce higher heat transfer rates will less air flow or power used due to clever exchanges of air velocity to static pressure.

Further reading on ducting: 
* https://www.racetechmag.com/2017/08/willem-toet-explains-air-ducts/
* http://www.glasairproject.com/GlasairI/AirSig/CoolingSystems/cooling2/CoolingSystems2.htm

==Routing==
Coolant routing is largely a packaging concern. There are minor theoretical gains to be had in cooling performance if you minimize head losses. However, these are likely not big enough to gain points in competition, or seconds off in a dynamic event. Like most other fluid systems, routing can be done with hard lines or soft lines. The soft lines are often silicone similar to those seen in aftermarket applications, as they do not need to withstand high pressures or a caustic fluid like gasoline. Hard lines are often connected by short sections of silicone tubing.

Keeping routing short and straight will reduce weight. Reducing bends will drastically reduce the difficulty to bleed the system. In addition, any routing section that is not monotonic will trap air bubbles. It is recommended that the fill point of the system be the highest point to aid in complete filling.
===Hosing===
Coolant hosing comes in 2 types: hard lines and soft lines. Hard lines are often aluminum due to their low cost and ease of bending. Soft lines are often silicone or rubber hosing, but the use of water as coolant allows for lower spec lines than a production or high performance industry automobile. The stock motorcycle coolant lines are pre-formed rubber lines and are more than capable of being used for FSAE.

Hard lines weigh less per foot of distance and are often cheaper to purchase. However, they require more planning to execute. Soft lines can be routed around much more complicated geometry without planning the routing before hand.

===Filling and Bleeding===
For the coolant system to run correctly, the system needs to be purged of air. A bleeder valve should be placed on the highest point in the system, often connected to the filler neck. You may have to turn the engine over a few times to flush it through the engine.

DON'T TAKE THE RADIATOR CAP OFF WHEN IT'S HOT. If one was to hypothetically remove the rad cap when the system is dangerously hot, they could cover it with a heavy cloth to shield themselves from the coolant that will come out. Do not do this. Under no circumstances is it advisable to attempt to service the system until it has cooled down to a safe level.

==Catch Can==
According to rules T.5.6, catch cans must meet the following criteria:
# Must have a minimum capacity of 10% of the fluid being contained or 0.9 liter, whichever is greater
# Capable of containing boiling water without deformation
# Located rearwards of the firewall below the driver’s shoulder level
# Positively retained, using no tie wraps or tape
# Must vent through a hose with a minimum internal diameter of 3 mm down to the bottom levels of the Chassis.

There are commercially available solutions for automotive catch cans. There are many ways to make lighter or more package-able catch cans than what is sold off the shelf.


==Simulation/Analysis==
The system can be modeled parametrically to analyze how sensitive your setup will be to changes in each of these parameters. You will need to have the correct (or close enough) values for your mass flow rates for water and air, coefficient for thermal conductivity, area and heat input.
In order to verify the model, tests will have to be performed, either on a dyno or on a vehicle. You must gather temperature data before and after the radiator.

===Thermal Resistance Circuit===
The easiest way to model heat transfer is with a resistance based electrical analogy. A thermal mass can be looked at as a single capacitor, a heat transfer boundary can be looked at as a resistor, and a heat source, unsurprisingly, as a DC source. This allows a number of elegant simplifications to heat transfer analysis.

Thermal resistance is how the temperature difference required over a boundary to conduct a certain amount of heat (°C/W). Thermal capacitance is a heat capacitance, the mass of a object times the specific heat (J/°C).

An alternative but almost identical analytical lens is to use conductances instead of resistances. Thermal conductance is the inverse of thermal resistance (W/°C). For conductive heat transfer, the conductance is k/t. For convective heat transfer, the conductance is hA.

===Battery Thermal Analysis===
Teams should ensure their accumulator does not enter thermal runaway. Important in this endeavor will be analyzing the internal heat generation of the cells, and the heat rejection of the accumulator. Often some information about heat generation can be found from the manufacturer, but as the DCIR of a cell is highly temperature dependent, often the manufacturer's data is insufficient for analyzing a large range of temperatures.

==Data and Data collection==
see [[:Category:Data Acquisition|Data Acquisition]]

The least amount of data needed for verification of coolant performance is the temperature of the engine coolant (ECT) taken from the engine itself. Stock motorcycle engines will provide an ECT sensor. To characterize radiator performance, the team will need to add temperature sensors before and after the radiator. It is recommended to have a pressure data and if possible flow data on vehicle.
=Other applications=
===Brake cooling===
Brakes convert the kinetic energy of the car into heat. The heat will either go into the brake pads or the brake rotors. Different pad materials need different temperatures to reach peak stopping power. If the brakes are too hot, they will lose braking performance known as brake fade.

The rotors are spinning disks of metal, there will be some natural convection as the car is driven around. This can be modeled in software to give an approximate look at thermal performance in the brakes. However, unless the model has been verified against existing data, there is only one way to truly determine thermal behavior of the brakes and that is to physically test them. To find the temperature, the team can use an IR thermometer to periodically take rotor temperature, or the team can employ the use of brake temperature paint or stickers that will change color depending on how hot the system gets.

Due to the unique nature of every car, it cannot be universally recommended to use or not to use ducting to force a higher rate of convection to the brakes. Most teams do not find this necessary as the wheel well is open enough to facilitate sufficient passive cooling.
===Oil cooling===
Many engines have an OEM oil/water heat exchanger. From my experience with the 600rr, these are very compact and well integrated with the original powertrain system. Most teams use what is close to the manufacturer's recommended engine oil and the water coolant should be a perfectly fine substitute for the antifreeze solution on the OEM bikes.

===Intercooler===
===Driver cooling===
lmao
=References=
[[Category: Internal Combustion]][[Category: Electric Vehicle]]

Cooling

2024-04-02T13:37:23Z

SpookySimon: /* Fluid Flow Rates */ gormatting

A '''cooling''' system is needed to keep the [[Engine|engine]] or motors within their operational temperature range.

Of all chemical energy burned in the engine, the largest fraction of the energy goes into heating the engine and the exhaust<ref name=heywood>Heywood, John B. "Chapter 12: Engine Heat Transfer" Internal Combustion Engine Fundamentals, McGraw-Hill, 1988, pp. 668-711.</ref><ref>http://web.mit.edu/2.61/www/Lecture%20notes/Lec.%2018%20Heat%20transf.pdf slides 3,4 are taken from Heywood textbook if you don't have a copy</ref>. Please refer to chapter 12 of the textbook ''Internal Combustion Engine Fundamentals'' by Heywood for reference and detailed information on engine specific heat transfer, this page will be kept as a FSAE specific reference page.

EV Cooling follows much of the same principals with the total heat rejection on a smaller scale, however there is generally no OEM radiator to compare to. Additionally, EVs have the option to use oil as a cooling liquid instead of water.
=Theory=
Cooling systems are designed to dissipate the unwanted thermal energy. Systems are often designed around heat exchangers (HEXs), allowing for efficient exchange of heat from a hot fluid to a cooler one. There are three main methods of heat transfer;
* Conduction: Heat transfer over a temperature differential without motion between the materials
* Convection: Heat transfer over a temperature differential with fluid motion between the materials
* Radiation: Heat transfer in the form of electromagnetic radiation absorbed and emitted by bodies
A heat exchanger (HEX) is normally designed to facilitate the heat transfer between two fluids using conduction and convection. The most common HEX in FSAE/FS is a water to air cooler, meaning it transfers heat between the hot water and the cooler air. These HEXs have a few distinct characteristics, full metal construction, thin metal fins in the streamwise direction, water inlets on top and bottom, with air inlets on the front and back. The metal construction is advantageous because of its high conductive heat transfer coefficient and its low specific heat. These factors allow the metal rapidly conduct heat from the hotter internal water channels to the cooler metal fin tips. Aluminum is nearly universally used in automotive radiators. While materials such as copper may notionally provide more cooling due to higher thermal conductivity, the thermal resistance of aluminum sheet metal is so low that the heat transfer from the water circuit to the air is limited by the convective coefficients. Aluminum also is light and strong as fins or sheets. The fin structure is to maximize convection heat transfer by increasing the surface area the air flows over. The convection heat transfer coefficient is also a function of the airspeed passing the fin, allowing for 'forced convection' where a fan and or vehicle speed is used to impart an inlet speed to the system. Radiator performance varies widely based upon water channel sizes, fin spacing, and a plethora of other characteristics.

For a more detailed understanding of theory, any heat transfer textbook such as ''Incropera and Dewitt ''will serve. ''Kays and London'''s heat exchanger text is invaluable as a practical reference. It includes heat transfer coefficients for various fin and tube geometries. A car radiator is considered a cross-flow radiator with both fluids unmixed. It is possible to measure the geometry of your radiator's fins, determine what type of fin geometry you are using, and then look up the appropriate set of coefficients for a rather robust heat exchanger model.

=System Design=
The amount of thermal power that the engine puts into the water has to be the same as the thermal power the radiator dissipates ''at steady state''. FSAE rules state that the system must be cooled using water only(IC and EV) or oil(EV). The coolant can not contain additives. Additionally the system must be able to pass a 45 degree tilt test with no leaks.

There are a couple of things that influence how much power the cooling system has. Because the heat generation is not a tunable parameter in the cooling system design, the parameters that can be easily adjusted are:
* Radiator Choice (Type, Size, Number)
* Radiator Packaging
* Radiator Angle
* Radiator Ducting
* Fan Sizing
* Fan Control

==Cooling Power Determination==
===Combustion===
A rule of thumb is 1/3 of the power you put into the engine in the form of fuel flow turns into heat. 1/3 becomes the power that turns the wheels and the last third comes out as exhaust enthalpy. This ratio means that the power the radiator has to dissipate is approximately the same as the power sent to the wheels. The actual cooling load can range between 60 percent to 20 percent of the fuel LHV depending on the engine and driving conditions: a throttled engine will be much less thermally efficient<ref name = heywood/>.

Keep in mind though that you don't drive full throttle all the time, so you should verify any cooling assumptions made during design with physical tests.

Finding average power output of the engine is one way to determine an approximate necessary cooling power for the engine. This can be accomplished by measuring fuel consumption or engine torque/vehicle velocity (P = FxV).
===EV===
The main heat generating components are the motor and motor controller. Conservative rules of thumb put the ballpark efficiencies at about 90% for both components. The heat generated by this powertrain would be about 15 kW<ref>According to the equation Q = Pelectric,input*(1 - ηcontroller * ηmotor) = 80*(1-0.9*0.9) = 15.2. Some papers use Q = Pelectric,input*[(1 - ηcontroller) + ηcontroller * (1 - ηmotor)] which is numerically equivalent</ref> when running at max power. A better estimate is 30kW average draw for the traction system<ref>Chiu, Harriet A. ''Design of a FSAE Cooling System''. 2019. MIT </ref> which yields a ballpark heat generation of ~6kW. This is likely higher than most teams will see.

A more thorough method is to use data from previous years, or that generated by a [[Introduction to VD Simulation | lap sim]], coupled with the efficiencies given on the motor/motor controller datasheets if available to model the generation over a lap<ref>LaMarre, Jeff. "FSAE Electric Vehicle Cooling System Design". 2015. UAkron</ref>.

EV teams also need to consider cooling the [[Battery_pack | battery]]. This is generally best considered as a battery design problem, as it requires a different approach to that of the motor.

==Radiator Choice==
The radiator for most teams is outside of the scope of custom design and production. Therefore, many teams have limited to no ability to tune radiator parameters, and the choice of which radiator to run becomes the main design choice. Radiator selection can be done by size: length, width, and thickness. Radiator dimensions are not created equal as lower temperature water will be cooled less than high temperature water. The focus should be on getting more mass flow of hot water. On a downflow radiator, this means radiator width will often be more impactful than radiator length. A longer radiator forces water to travel further through the radiator, causing a greater ΔT between the inlet and outlet, and a lower average water temperature. The width of a radiator is analogous to the diameter of a pipe, the larger the width, the more water can flow through the radiator at a time. The thickness of the radiator will increase the massflow of the water through the radiator and the amount of time a quantity of air is in contact with the radiator, but can negatively impact the massflow of air through the radiator.

The two types of radiator are cross flow and down flow. The difference in performance is insignificant. A downflow radiator has water enter the top and go to the bottom in one pass. Crossflow radiators force water through the radiator sideways and can include multiple passes. Downflow radiators are most common in FSAE as they are usually taller and skinnier and will fit on the side of the vehicle without increasing frontal cross sectional area.

Fin density is an important part of radiator design, but is not tunable, and not worth the time to specify if buying an off-the-shelf solution.

You can also purchase radiators by specifying the approximate engine power or by contacting a radiator supplier for assistance.

==Radiator Placement==
'''Side''' The most common radiator placement in FSAE is on the side of the vehicle, usually within the sidepod. This is a space that is usually free of other systems, somewhat unobstructed airflow, and for most bike engines it is a favorable routing position.

The sidepod design allows the team to guide air into the radiator. A properly constructed duct will dramatically increase cooling power and can reduce drag.

'''Rear''' A few teams rear-mount the radiator. Rear mounting is usually to take advantage of diffuser airflow, free up space on the side for aero devices, or to tune weight distribution. The disadvantages can be the reduced free air flow, yaw inertia, and possible routing complications.


'''Multiple''' 
Common FS/FSAE electric mounting scheme is to run two symmetric radiators<ref>https://www.instagram.com/p/B8jcYNqhux2/?igshid=1hwa03kwfnw3</ref>.
==Fluid Flow Rates==
Tuning radiator performance is largely balancing the flow rates of the water and the air passing through the radiator. For analysis, heat exchangers use a term called capacity rate which is the mass flow rate times the specific heat of the fluid. An over-simplified way to think about this is as if the fluid are conveyer belts for "heat units", the specific heat capacity is how many "heat units" can fit on the belt at a time and the mass flow rate is how fast the belt is going. Heat capacity rate is defined as:
: C = ṁ * cp

The maximum possible heat transfer by a heat exchanger will be limited by the smallest heat capacity rate as seen by the equation:
: Qmax = Cmin * (thot,inlet - tcold,inlet)

The limiting factor in our analogy will be whichever conveyer belt is filled up first. The ratio of flow rates is called Capacity-Rate Ratio and is the lower flow rate Cmin over Cmax. The effectiveness of the heat exchanger will be a function of this ratio. A few assumptions will be important in the flow rate discussion here: (1) The engine is designed such that the water inlet temperature to the radiator (thot,inlet) will be the same temperature regardless of the water flow rate and (2) The inlet air temperature will be independent of the air flow rate.
The above equation tells us two things: heat transfer is limited by one of the mass flow rates, and that increasing the lowest heat capacity rate will increase our heat transfer rate.
We can discuss the impact of changes to a single fluid flow rate interchangeably with capacity rate if we assume the heat capacity of the fluid stays constant, but not when comparing the capacity rates of two fluids.
===Water===
Tuning water mass flow rate is about finding the right balance: if you have 0 water flow rate, you'll get close to 0 cooling no matter what else you do. Hot water will stay in the engine, cold water will stay in the radiator. On the other end, there is a practical limit of flow rate due to pressure rating of the radiator and pump specifications. Between the extremes, an increase in water flow rate will increase heat transfer until it is no longer the limiting factor. If you have a properly sized water pump and swap to a bigger one, you'll see limited gains.

Practically speaking: Upgrading a water pump can be a serious investment in time and resources. The water pumps on the stock engine are designed to pump coolant for an unrestricted engine running at significantly higher power for long periods of time specifically on sport bikes like the YZ450 or CBR600RR. Therefore, it is unlikely but certainly possible that upgrading the water pump is a good step for your team.

Note: The stock CBR 600RR water pump generates 30-60 Lpm<ref>https://www.facebook.com/photo/?fbid=10150829256503036&set=a.10150813204983036</ref>. With a few assumptions, we can calculate the maximum ballpark capacity rate for a CBR:
* Volumetric flow rate of 60 LPM
* 1kg/L density of water
* Temp near 100C<ref>cp of water is slightly temperature dependent at these temps. The higher the inlet water temp of the hot fluid, the higher the max heat transfer rate. We cannot use a higher temperature for FSAE coolant than 100C without cheating.</ref>
* cp of 4.2157 KJ/kg*k
This yields a maximum heat capacity rate of 4.2157 kW/k

===Air===
The specific heat capacity (cp) of air is 1.006 between 0 and 35C<ref> It also only increases to 1.007 even past 45C so I think it's more than fair to assume constant for use in FSAE analysis https://www.engineeringtoolbox.com/air-specific-heat-capacity-d_705.html</ref> so you'll need about 4 times the mass flow rate of air to reach heat capacity rate parity with water, or, assuming ~1.2g/L density of air, more than 3300 times the volumetric flow rate to reach parity.

Sufficient air flow for adequate cooling is easy to achieve, but making a simple mistake that costs cooling performance is equally easy. The first decision that will affect the radiator performance is location of the radiator, this will dictate how much clean air the radiator will see during driving operation. If packaged behind the car, it is possible that the radiator will see increased air temperature because of the engine. The main ways the team can achieve adequate airflow once the radiator has been located on the vehicle are angling the radiator, utilizing fans, and adding a duct or shroud.

'''Angle of radiator''' Angling a radiator will allow a larger radiator area to fit in a similar frontal cross sectional area, effectively fitting a larger radiator in the same space. Yes, this will sacrifice fore/aft space, but this space should be free of obstruction anyways in order to allow for free air-flow. You can angle it to about 45° relative to the airflow both vertically and horizontally without any significant loss in cooling power<ref>Fenske, Jason. "Formula One Radiator Technique - Explained". https://www.youtube.com/watch?v=l3SJlGqc0P0</ref>. Tilting it in the vertical and one of the horizontal axes will allow a radiator of ''double'' surface area in the same frontal area, or to halve the frontal area with the same radiator.

'''Fans''' Because air capacity rate is likely to be a limiting factor, the vehicle will need a way to keep air flowing through the radiator when the vehicle is not moving. Fans attached to the back of the radiator are instrumental in vehicle operation. Fans should be sized for their airflow ratings, and attached such that all the air drawn by the fan is pulled through the radiator, this is done using a shroud. It may be necessary due to electrical draw constraints to only run the fans when needed. This can be accomplished by using the ECU to control a relay based on temperature or speed or by having the driver control them according to a light in the cockpit.

Because the margin between running temperature (about 90C) and disaster (100C) is so tight (check these numbers), the fans might have to run fairly aggressively especially on a hot day when chaining autocross laps. A tight seal between fan shroud and the radiator is key to avoid leakage. Spacing between the fan and radiator is also key: you want a uniform pressure difference across the radiator to achieve a uniform flow rate.

'''Ducting/Shrouding''' A shroud seals the fan to the radiator ensuring all of the air flow generated by the fan goes into raising the mass flow through the radiator. A duct channels air from the environment through the radiator and back to the environment. A properly designed duct can produce higher heat transfer rates will less air flow or power used due to clever exchanges of air velocity to static pressure.

Further reading on ducting: 
* https://www.racetechmag.com/2017/08/willem-toet-explains-air-ducts/
* http://www.glasairproject.com/GlasairI/AirSig/CoolingSystems/cooling2/CoolingSystems2.htm

==Routing==
Coolant routing is largely a packaging concern. There are minor theoretical gains to be had in cooling performance if you minimize head losses. However, these are likely not big enough to gain points in competition, or seconds off in a dynamic event. Like most other fluid systems, routing can be done with hard lines or soft lines. The soft lines are often silicone similar to those seen in aftermarket applications, as they do not need to withstand high pressures or a caustic fluid like gasoline. Hard lines are often connected by short sections of silicone tubing.

Keeping routing short and straight will reduce weight. Reducing bends will drastically reduce the difficulty to bleed the system. In addition, any routing section that is not monotonic will trap air bubbles. It is recommended that the fill point of the system be the highest point to aid in complete filling.
===Hosing===
Coolant hosing comes in 2 types: hard lines and soft lines. Hard lines are often aluminum due to their low cost and ease of bending. Soft lines are often silicone or rubber hosing, but the use of water as coolant allows for lower spec lines than a production or high performance industry automobile. The stock motorcycle coolant lines are pre-formed rubber lines and are more than capable of being used for FSAE.

Hard lines weigh less per foot of distance and are often cheaper to purchase. However, they require more planning to execute. Soft lines can be routed around much more complicated geometry without planning the routing before hand.

===Filling and Bleeding===
For the coolant system to run correctly, the system needs to be purged of air. A bleeder valve should be placed on the highest point in the system, often connected to the filler neck. You may have to turn the engine over a few times to flush it through the engine.

DON'T TAKE THE RADIATOR CAP OFF WHEN IT'S HOT. If one was to hypothetically remove the rad cap when the system is dangerously hot, they could cover it with a heavy cloth to shield themselves from the coolant that will come out. Do not do this. Under no circumstances is it advisable to attempt to service the system until it has cooled down to a safe level.

==Catch Can==
According to rules T.5.6, catch cans must meet the following criteria:
# Must have a minimum capacity of 10% of the fluid being contained or 0.9 liter, whichever is greater
# Capable of containing boiling water without deformation
# Located rearwards of the firewall below the driver’s shoulder level
# Positively retained, using no tie wraps or tape
# Must vent through a hose with a minimum internal diameter of 3 mm down to the bottom levels of the Chassis.

There are commercially available solutions for automotive catch cans. There are many ways to make lighter or more package-able catch cans than what is sold off the shelf.


==Simulation/Analysis==
The system can be modeled parametrically to analyze how sensitive your setup will be to changes in each of these parameters. You will need to have the correct (or close enough) values for your mass flow rates for water and air, coefficient for thermal conductivity, area and heat input.
In order to verify the model, tests will have to be performed, either on a dyno or on a vehicle. You must gather temperature data before and after the radiator.
===Thermal Resistance Circuit===
The easiest way to model heat transfer is with a resistance based electrical analogy. A thermal mass can be looked at as a single capacitor, a heat transfer boundary can be looked at as a resistor, and a heat source, unsurprisingly, as a DC source. This allows a number of elegant simplifications to heat transfer analysis.

===Battery Thermal Analysis===
Teams should ensure their accumulator does not enter thermal runaway. Important in this endeavor will be analyzing the internal heat generation of the cells, and the heat rejection of the accumulator. Often some information about heat generation can be found from the manufacturer, but as the DCIR of a cell is highly temperature dependent, often the manufacturer's data is insufficient for analyzing a large range of temperatures.

==Data and Data collection==
see [[:Category:Data Acquisition|Data Acquisition]]

The least amount of data needed for verification of coolant performance is the temperature of the engine coolant (ECT) taken from the engine itself. Stock motorcycle engines will provide an ECT sensor. To characterize radiator performance, the team will need to add temperature sensors before and after the radiator. It is recommended to have a pressure data and if possible flow data on vehicle.
=Other applications=
===Brake cooling===
Brakes convert the kinetic energy of the car into heat. The heat will either go into the brake pads or the brake rotors. Different pad materials need different temperatures to reach peak stopping power. If the brakes are too hot, they will lose braking performance known as brake fade.

The rotors are spinning disks of metal, there will be some natural convection as the car is driven around. This can be modeled in software to give an approximate look at thermal performance in the brakes. However, unless the model has been verified against existing data, there is only one way to truly determine thermal behavior of the brakes and that is to physically test them. To find the temperature, the team can use an IR thermometer to periodically take rotor temperature, or the team can employ the use of brake temperature paint or stickers that will change color depending on how hot the system gets.

Due to the unique nature of every car, it cannot be universally recommended to use or not to use ducting to force a higher rate of convection to the brakes. Most teams do not find this necessary as the wheel well is open enough to facilitate sufficient passive cooling.
===Oil cooling===
Many engines have an OEM oil/water heat exchanger. From my experience with the 600rr, these are very compact and well integrated with the original powertrain system. Most teams use what is close to the manufacturer's recommended engine oil and the water coolant should be a perfectly fine substitute for the antifreeze solution on the OEM bikes.

===Intercooler===
===Driver cooling===
lmao
=References=
[[Category: Internal Combustion]][[Category: Electric Vehicle]]

Scrutineering

2024-03-27T20:02:55Z

SpookySimon: /* Tractive System */ link to my design judges article on hv interlock

Each competition will have a different scrutineering method, and each Vehicle Type (EV, CV and DV) will do so. It is absolutely essential to have multiple team members read the competition rules in their entirety and then work through the entire scrutineering checklist in advance of inspection at competition to avoid spending valuable time making modifications to the vehicle. Most teams will have to make very minor adjustments to firewall or similar areas but keeping those changes at scrutineering minimal is a critical goal.
=Scrutineering by Competition=
==FSAE==
===Gear===
===Inspection===
If your team is like the vast majority of teams that show up at competition, the car and the team will have both been through a lot. This may be because it has lasted 1000s of km of testing or because you finished the night before at 4am. There will almost always be minor infractions on some part for some reason. This is racing, that's just how it is.

Of course, in theory, your car should be 100% up to code, but the inspectors are only human and minor, inconsequential, non-safety rule violations can slip through the cracks. One of the peculiarities of tech inspection is that the more mistakes are found by inspectors, the more mistakes they are likely to find. This is because the more time someone spends looking for minor rule violations, the more they will find. Usually inspectors continue to poke and prod at the car while the team is fixing one issue.

Teams are not allowed to work on the car during technical inspection at the Michigan FSAE EV competition in June.
====Common and Easily Fixable Mistakes====
There are a number of key areas that are commonly called out in tech inspection.
 
'''Line of Sight to Driver'''
 
Most common infraction, easiest fix. Bring enough of your favorite tape to tech and be ready to use it.
* Fuel lines
* catch can tubes
'''Fasteners'''
 
These are a longer, more annoying fix for both the team and the inspectors, you wanna fix these before getting teched. If one is found, the inspectors will likely check ''all'' of your bolts.
* No positive locking on critical fasteners
* Incorrect type of locking for location
** some locations such as the brake system and systems near the engine require non-plastic locking features. I have seen a fuel rail nylock taken off by hand while being inspected.
* [[Safety Wire|Safety wire]] incorrect
** It is very uncommon to see students use safety wire to the standards of industry motorsports or aviation. This is a grey area for rules interpretation by tech inspectors and they will pass most safety wire applications that will work in a pinch or are close to correct.
* Bolts too short in very visible locations like suspension pickup points
'''Gas Tank'''
 
Usually these are resolved by removing a bolt, swapping a clamp, or cutting bodywork, easy fix, but also easy to avoid by checking in paddock
* Rigid mounting = no no
* Sight tube too short
* Sight tube behind bodywork
* Bodywork makes filler neck difficult to access
'''Driver Harness'''
 
If your team gets dinged for these, you likely wont be able to fix in the paddock anyways, and will need someone to show you how to do it properly. Inspectors will walk you through it if needed, it happens all the time.
* Harness not looped through brackets right
* Arm restraints looped around wrong belt
'''Intake'''
 
Rigid mounting is easy to fix, usually involves loosening and padding the restrictor mount. Not worth worrying about in the paddock too much.
* Restrictor rigidly mounted to vehicle, no isolation
* Missed critical fasteners
'''Drivetrain Shields'''
 
This is often a very difficult fix while getting teched and will get you sent back to the paddock to fix. Better to worry about the day before at the ''latest'', not a good morning-of fix.
* Too narrow in y (need 3x width)
* No guard in front of front sprocket
'''Fuel and Cooling lines'''
 
Some inspectors make this their whole thing. Bring the right clamps to comp, and some spare hoses.
* Using worm gear clamps on fuel lines
* Sight line to driver
'''Aero'''
 
These are frequently an easy fix, often sharp edges are taped, wobbly wings are just tightened. Easy enough to fix, easier to fix in the paddock.
* Sharp edges on forward facing edges
* Wobbly wings

====Egress====
Each driver needs to pass an egress test to be allowed to drive in competition. This is usually checked at the same time as all the Driver-In-Car scrutineering such as driver harness and helmet clearance. Inspectors will allow as many egress attempts as needed (as long as its reasonable, not like 4 hours). Only one driver needs to pass to complete the rest of technical inspection (sound, tilt, brake) and the team can return at any time to get the rest certified.

'''Tips'''
A few small tweaks to the strategy can help teams pass egress.
* Practice before showing up to competition
* Tighten the harness as snug as possible, the tighter the harness is, the faster it will get out of the way when the driver activates the quick release.
* Stay calm, drivers who panic make small mistakes like missing the quick release on the harness or getting a foot caught on the steering column. These almost always end up slower than smooth/calm attempts
* The inspectors will help you through the steps if needed and there's no penalty for a failure to egress in the necessary time.

===Noise===
===Tilt===
===Brake===

==Formula Student Germany==
The FSG technical inspection is divided into the following parts<ref>FS Rules 2020 V1.0. (2019, September 13). Retrieved from https://www.formulastudent.de/fsg/rules/</ref>:
{| class="wikitable" style="width: 752px; border-color: #000000;" data-mce-style="width: 752px; border-color: #000000;"
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; width: 170px; text-align: center;" data-mce-style="height: 16px; width: 170px; text-align: center;"|'''CV'''
| style="height: 16px; width: 187px; text-align: center;" data-mce-style="height: 16px; width: 187px; text-align: center;"|'''EV'''
| style="height: 16px; width: 160px; text-align: center;" data-mce-style="height: 16px; width: 160px; text-align: center;"|'''DV'''
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="text-align: center; height: 16px; width: 517px;" colspan="3" data-mce-style="text-align: center; height: 16px; width: 517px;"|''' Pre-Inspection '''
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; width: 170px; text-align: center;" data-mce-style="height: 16px; width: 170px; text-align: center;"|###
| style="height: 16px; width: 187px; text-align: center;" data-mce-style="height: 16px; width: 187px; text-align: center;"|Accumulator Inspection
| style="height: 16px; width: 160px; text-align: center;" data-mce-style="height: 16px; width: 160px; text-align: center;"|###
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; width: 170px; text-align: center;" data-mce-style="height: 16px; width: 170px; text-align: center;"|###
| style="height: 16px; width: 187px; text-align: center;" data-mce-style="height: 16px; width: 187px; text-align: center;"|Electrical Inspection
| style="height: 16px; width: 160px; text-align: center;" data-mce-style="height: 16px; width: 160px; text-align: center;"|###
|- style="height: 5px;" data-mce-style="height: 5px;"
| style="height: 5px; width: 517px; text-align: center;" colspan="3" data-mce-style="height: 5px; width: 517px; text-align: center;"|'''Mechanical Inspection '''
|- style="height: 0.262497px;" data-mce-style="height: 0.262497px;"
| style="height: 0.262497px; width: 170px; text-align: center;" data-mce-style="height: 0.262497px; width: 170px; text-align: center;"|###
| style="height: 0.262497px; width: 187px; text-align: center;" data-mce-style="height: 0.262497px; width: 187px; text-align: center;"|###
| style="height: 0.262497px; width: 160px; text-align: center;" data-mce-style="height: 0.262497px; width: 160px; text-align: center;"|Driverless Inspection
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; text-align: center; width: 517px;" colspan="3" data-mce-style="height: 16px; text-align: center; width: 517px;"|''' Tilt Test '''
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; text-align: center; width: 517px;" colspan="3" data-mce-style="height: 16px; text-align: center; width: 517px;"|''' Vehicle Weighing '''
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; text-align: center; width: 170px;" data-mce-style="height: 16px; text-align: center; width: 170px;"|Noise Test
| style="height: 16px; text-align: center; width: 187px;" data-mce-style="height: 16px; text-align: center; width: 187px;"|Rain Test
| style="height: 16px; width: 160px; text-align: center;" data-mce-style="height: 16px; width: 160px; text-align: center;"|###
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; text-align: center; width: 517px;" colspan="3" data-mce-style="height: 16px; text-align: center; width: 517px;"|'''Brakes Test'''
|- style="height: 16px;" data-mce-style="height: 16px;"
| style="height: 16px; width: 170px; text-align: center;" data-mce-style="height: 16px; width: 170px; text-align: center;"|###
| style="height: 16px; width: 187px; text-align: center;" data-mce-style="height: 16px; width: 187px; text-align: center;"|###
| style="height: 16px; width: 160px; text-align: center;" data-mce-style="height: 16px; width: 160px; text-align: center;"|EBS Test
|}

=Scrutineering by Vehicle Class=
==Electric Vehicle==
===Preinspection===
===Accumulator Inspection===
====General====
Please only bring a finished and tested accumulator to a competition. How can you prove to others that it works if even you do not know yet? Always wear safety goggles! Always wear insulating gloves if even one of your maintenance plugs are connected! Be familiar with your design, it will be obvious to the scrutineer, and possibly dangerous if you do not know your own accumulator. Be prepared, read the inspection sheets, have your documents and datasheets ready. You have a fixed time to finish, after that you are back in the queue.
====Equipment====
Have your safety gear ready, you will need it anyway. Have your tools ready, you will open up the accumulator and possibly the charger. Bring a laptop and whatever hardware (can, ethernet, wifi, etc.) that you need to connect to the accumulator. Bring your datasheets (paper or digital) and actually know what is in them.
====Charger assembly====
Must be a closed system Have all your safety systems integrated and show them working. (interlock, shutdown, imd) All metal parts must be grounded to PE.
====Accumulator container====
Your SES must be approved! Please submit it in time, depending on the competition your scrutineering might be cut short here. Put all necessary markings on your container.

HousingRoll your fully assembled accumulator in to scrutineering on your handcart. Every panel/cover/lid has to be fastened. If you have 20 screws for the top it is usually fine if you dont use all of them since you will have to disassemble the battery but it must be rigid at all times. Fix the accumulator to the handcart, no moving, sliding or tilting. 

After opening the battery remove the maintenance plugs.
====Assembly====
====Wiring====
====Indicator Light====
====AMS====
====Charger Shutdown Circuit====
====IMD====
====Handcart====

===Tractive System===

====Outboard Motor HV Interlock ====
* see DesignJudges article here: https://www.designjudges.com/articles/outboard-motor-hv-interlock-circuit

===Low Voltage Sytem===
===Mechanical===
===Noise Test===
===Rain Test===
===Brake Test===
==Combustion Vehicle==
===Preinspection===
===Tractive System===
===Low Voltage Sytem===
===Mechanical===
===Noise Test===
===Rain Test===
===Brake Test===
==Driverless Vehicle==
===Preinspection===
===Tractive System===
===Low Voltage Sytem===
===Mechanical===
===Noise Test===
===Rain Test===
===Brake Test===
[[Category:Competition]]

Oil

2024-03-27T20:00:18Z

SpookySimon: references section

'''Oil''' is needed to ensure the engine's continued function. The oiling system will often make a small or negligible impact on horsepower from the engine, unless the engine blows up from a lack of adequate oil pressure, in which case you will have zero horsepower. Careful design is needed to make sure the engine won't explode in the middle of a corner.
==System design==
[[File:Oil system.PNG|right|middle|thumb|Oil System Differences]]
The vast majority of FSAE internal combustion cars use [[Engine|motorcycle engines]]. One of the key differences between motorcycle engines and car engines is how the oil system functions.
===Wet Sump===
[[File:Wet sump.PNG|right|middle|thumb|Wet Sump Schematic]]
In a stock motorcycle engine, the oil is stored in an internal oil pan. This is called a “wet sump” oil system. On a motorcycle, this design continues to function during hard lateral turns because the motorcycle itself leans into the turn, allowing the oil pickup to remain submerged during the turn. In a four wheeled vehicle, the engine cannot tilt into the turn, and the oil is forced against the side of the pan, sometimes away from the oil pickup. This leads to oil starvation, which leads to low oil pressure.
Wet sump systems can be successfully used in FSAE cars, but usually significant alterations to the stock oiling system are needed, especially if the team also wants to shorten the oil pan to lower the CG of the engine or for packaging reasons. Redesigning the oil pan from scratch is common. Baffles can be added to decrease starvation in corners. To significantly shorten the height of the oil pan, the oil pickup will likely also need to be shortened. Filling the engine past the level expected by the manufacturer is also possible, as long as the crankshaft doesn't hit the oil and whip it into a froth.
====Oil Accumulator====
One middle ground between a wet sump and a dry sump is a wet sump system with an oil accumulator (often known by the proprietary brand name Accusump). The accusump is an external oil reservoir system that sends oil to the engine when oil pressure goes below a certain threshold. When the driver leaves the corner, the oil returns to the reservoir. This way, the engine is guaranteed a certain oil pressure, until the oil reservoir runs empty, which can happen in long sweeping corners. Accusumps are more common on road racing cars, where corners can be much longer than on autocross tracks.

===Dry Sump===
[[File:Dry sump.PNG|right|middle|thumb|Dry Sump Schematic]]
In a dry sump oil system, the oil for the engine is stored in an external reservoir. The oil that collects at the bottom of the engine is quickly removed by a scavenging pump, and routed into the external reservoir from which the supplies for the engine and the turbocharger are drawn. A common industry solution, a dry sump is often used in very high performance engines for a variety of reasons, including reducing the load on the engine by pumping the oil electrically, or reducing the frictional work the engine has to overcome by reducing windage. An advantage of a dry sump for FSAE is that the pan height can be reduced due to the external reservoir replacing the wet sump. This eliminates the oil starvation problem during cornering and brings the engine closer to the ground, lowering the [[Center of Gravity|center of gravity]]. A dry sump is common in FSAE for forced induction applications, as high lateral accelerations reached in the FSAE competition greatly increase the chances of temporary oil starvation of the turbocharger<ref>https://dspace.mit.edu/handle/1721.1/36310</ref>.

The main downside to a dry sump is the large oil tank needed to ensure adequate oiling performance (and to meet the rules), which adds weight and can be hard to package.

==Oiling for Turbochargers==
The engine has a robust internal oil management and supply system, so a brief or inconsistent oil supply will have limited consequences for the engine itself. However, the turbocharger is spinning at well over 200,000 rpm, meaning even a small perturbation in oil supply will spell disaster for the bearing system. [citation needed, our source this in our senior proj was alumni communications]
=References=
<references/>
[[category: Internal Combustion]]

Bearings

2024-03-21T19:00:54Z

SpookySimon: /* Spherical Bearings and Rod Ends */ calling out broken link

==Spherical Bearings and Rod Ends==
Used on the ends of suspension/steering tubes.
* [http://www.aurorabearing.com/pdf/rod-ends.pdf Rod ends for racing] <- broken link
===Suppliers===
* Aurora Bearing

==Radial and Axial Bearings==
Used on shafts. Radial Bearings are very common in Formula Student, while Axial bearings are rare. Typical unit has a hollow cylinder shape, with spherical balls or cylindrical rollers inside.

===Suppliers===
* Schaeffler (Includes FAG, and INA) [https://medias.schaeffler.us Schaeffler Catalogue]
* NSK
* SKF [https://www.skf.com/us SKF Catalogue (just use search)]
===Bearing Selection===
====Pre-Selection: Type of Bearing====
* The Schaeffler Pre-selection Chart on page 30 of the HR1 handbook<ref name=HR1/> provides a useful overview of the different types of bearings.
* Ball bearings are usually lighter, can run at faster speeds, and are lower friction than cylindrical roller bearings, but also have lower load capacity. Deep Groove Ball Bearings can take some axial load (see section 1.6, Page 36 of HR1<ref name=HR1/>), while non-locating roller bearings cannot take any. There will always be small amounts of axial load on shafts from small misalignments, which is why deep groove ball bearings are so common.
* Single row deep groove ball bearings come with different sized balls (and corresponding weights and sizes). From smallest to largest: 618XX, 619XX, 60XX, 62XX, 63XX. See section 1.2, page 216 of HR1<ref name=HR1/>.
* Suggestions from a FS Wiki Author of what teams could use:
** Bellcranks: Deep groove ball bearings
** Steering: Deep groove ball bearings, or needle bearings (in areas with 0 axial force)
** Drivetrain (such as differential mounting): deep groove ball bearings or roller bearings. Note that at least one bearing will have to be able to take the small axial load.
** Wheel Hubs: Angular Contact ball bearings or tapered roller bearings in an O configuration, Or buy an off-the-shelf wheel hub.

====Picking the Specific Size====
Suppliers have helpful tools. Can also use the Schaeffler HR 1 handbook.<ref name="HR1"/>
* [https://www.skf.com/group/products/rolling-bearings/principles-of-rolling-bearing-selection/bearing-selection-process SKF Bearing Selection Tool]
* [https://www.skfbearingselect.com SKF Bearing Select Tool]
* [https://medias.schaeffler.com/medias/la/start.do?property&lang=en&mediasS=bX-eGEFcBXnh&mediasCall Schaeffler Bearing Selection Tool]

===Tolerances and Fits===
Since bearings are standardized across suppliers, its okay to use a tool that isn't from the same company as the one that manufactures the bearings you actually buy.
====SKF Bearing Select Tool Method====
# Go to [https://www.skfbearingselect.com SKF Bearing Select Tool] Website.
# Select Roller Bearing (This includes deep groove ball bearings).
# Pick Single or Two on a Shaft.
# Pick the Bearing type in the drop down, then in the "Search Designation" type in the supplier part number, such as "608" or "6005", then hit next.
# Enter in the loads.
## For Single Bearings, Pick Calculations > Equivalent dynamic load AND Fits and Tolerances. Enter in Loads, then Calculate, then Next.
## For Two on Shaft, Enter the loads, hit calculate, then Next.
# On the Fits and Tolerances page, set "Standard fit recommendation" to ON.
====Schaeffler HR1 PDF Method====
Follow section 8.3 of the Schaeffler HR 1 Handbook<ref name="HR1"> https://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/catalogue_1/downloads_6/hr1_de_en.pdf</ref>.

# Search for the supplier part number on a supplier's catalogue like [https://medias.schaeffler.us/ Schaeffler's Medias Catalogue]. Bearings have standardized supplier part numbers across all suppliers, so it will be the same part number on SKF or NSK's website as well. Searching without the suffix for the seals (ie. "-ZZ" or "-2RS1") will improve the chances of at least finding the bearing of the correct size.
# The catalogue page for the specific bearing (like Schaeffler's Medias) should state the '''basic dimensions, and min/max radii of the housing''' etc. It may not contain the tolerances.
# In section 8.2-8.3 (pg 145) of the Schaeffler HR1 handbook<ref name="HR1"/> there will be '''tolerance info for the housing and shaft'''. Start with Table 1 to determine the loading condition. Then for radial bearings (the most common type) look at Table 2 for the shaft tolerance, and Table 4 for the housing tolerance.
# In the same Schaeffler HR1 handbook<ref name="HR1"/>, Section 8.6 has the more advanced '''GD&T''' (Table 10). To use Table 10, look up the Bearing Tolerance Class from the catalogue page specific to the bearings (from step 1 in this wiki guide), or just assume it's "normal 6X" or "PN", then Table 11 has the '''surface roughness tolerance''' (The diameter tolerance grade is from 4th column of Table 10).

=====Tolerances note: =====
Looser tolerances than those recommended by the manufacturer may be possible.

For '''drivetrain and wheel assemblies''', an increased interference may be possible when seating bearings into aluminum housings. Aluminum's high coefficient of thermal expansion allows it to expand significantly when heated. Do not wreck the heat treatment of the aluminum though. Additionally, having thin, lightweight aluminum bearing seats limits the residual stress from the press-fit and minimizes dimensional changes of the steel bearing race (compared to the same press-fit into thick steel housing), which would cause bearing issues such as friction and wear.

For '''bellcranks''' an increased interference may be possible for the same reasons as above. Additional clearance is possible due to the bearings moving at low speeds, only ever rotating <90deg and always being under preload.
When in doubt, follow the manufacturer's recommended tolerances.

=====Just give me some tolerances=====
If you want some housing and shaft diameter tolerances from strangers on the internet. If you run into issues, you have no one to blame but yourself.
* Wheel Bearings: N8/k6
* All Other Bearings: H8/h7

==See Also==
[[Compliance]]
==References==
<references />

[[Category:Engineering Materials‎]]