Fuel

Internal combustion engines can use a variety of fuels, the fuels available at US competitions are gasoline of octane ratings 93 and 100, and E85. Fuels and the fuel system are covered in IC.5 of the FSAE Rules. [find fs rules and say what they are here too] No fuel additives can be used

Chemistry

Gasoline

Although the gasoline supplied at the pump, and in US competition is 5-10% ethanol (check about in other countries), gasoline is typically approached chemically as pure octane.
$2{\text{C}}_{8}{\text{H}}_{18}(l)+25{\text{O}}_{2}(g)\rightarrow 16{\text{CO}}_{2}(g)+18{\text{H}}_{2}{\text{O}}(g)$

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.

Ethanol

The ethanol used in competition is E85, nominally 85% ethanol and 15% gasoline,.

System Design

Fuel Storage

I.C.1.2 Packaging Restrictions

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

volume determination

• ways to pick factor of safety
  • competition strategy

fixed volume only

Rigid Container

mounting

• cannot be stressed or loaded in any way by frame - no 3 hard points for mounting

material
form factor (exterior and interior)
sloshing is a meme

Bladder

just pour the gas in a kroger bag and let it flop in the wind /s

must be enclosed by a non-flexible container that is rigidly connected to the chassis and may be load bearing

Fuel Lines

Material	Internal Diameter [in]	Pressure [psi]	Cost [per foot]	Minimum Bend Radius [in]	Supplier	Notes
Hard Lines
Aluminum	3/8-1/2 (OD)	250	2+		Russell	link pressure rating is wall thickness dependent
Aluminum (0.035 wall thickness)	1/4-5/8 (OD)	200	0.68		Summit	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	unspecified	1.28		Summit	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	2		JEGS	link
Soft Lines
Nitrile Rubber*	3/8	50	0.88		JEGS	link
Nitrile* (Neoprene* cover)	1/8	50	0.8		Dayco	product details cannot buy direct
Buna-N*	3/16+	50	1.1	1.25	McMaster	link yarn reinforced
Buna-N*	3/4+	150	7	3	McMaster	link steel wire reinforced
Braided Lines
Nitrile Rubber* and Steel	1/4+	50	3.50+		Spectre	link
Nitrile Rubber* and Stainless Steel	0.22+ (4AN+)	1000	6+	2	Pegasus	link
PTFE and Stainless Steel	0.27+ (4AN+)	1320	11.3+	0.75	Pegasus	link
PTFE and Aramid	0.27+ (4AN+)	1320	21.3+	0.92	Pegasus	link
PTFE and Polyester	0.38+	305+	15.8+	2	Pegasus	link

* not compatible with e85

Hard Lines

only legends do this [citation needed] +weight
- cost
-manufacturing
+pressure
- not as reusable year to year

Soft Lines

pressure and solvent rated
e85 sucks for this
+cost
+manufacturing
+reusable year to year / design to design
-pressure

Braided

you're gonna poke you're eye out kid
- cost
- mfg
- i hate
+ reusable
+ pressure rated

Pump and Pressures

Low Pressure

under 10 bar
depends on injectors, we ran 3 bar, not sure what other people did
low pressure if for tbi and pi

Fuel Rail

critical fasteners

High Pressure

systems running at or above 10 bar high pressure is for di
FSAE - Fuel lines must be stainless steel hard-line or "Aeroquip FC807 smooth bore PTFE hose with stainless steel reinforcement and visible Nomex tracer yarn" (although you can run something similar if you get approval before comp)
supply before boost pump is considered low pressure

Fuel Rail

must be able to withstand max force not including cyl pressure
critical fasteners

---

talk about filters here? contribute to pressure loss...

Injectors

Placement

Throttle Body Injection

basically electornic carb

Port Fuel Injection

Fuel Injected into the ports just before entering the combustion chamber. Usually leads to well mixed charge [citation needed]

Direct Fuel Injection

big boys do this [citation needed]

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.

Firewall

Main page: Firewall

Fuel Strategy

Efficiency

BSFC

link for calc citations[1]
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

P_me (mean effective pressure)

n_mot (motor speed)

i_G (gear ratio for selected gear)

i_sec (FDR)

r_dyn (dynamic radius of tire)

V_d (displacement volume of engine)

i (constant for 4 stroke)

F_req (tractive force required)

p_me = (2pi*T_motor_required)/(V_d * i) = (2pi)/(V_d*i) * ((Freq * rdyn)/(i_G * i_sec) + T_low)

n_mot = (Velocity*i_g*i_sec)/(2*pi*r_dyn)

be (fuel consumption) usually experimentally determined

B_time = b_e*Pe/rho_fuel = b_e*p_me*V_d*n_mot*i/rho_fuel

B_distance = B_time/V

i = 0.5 for 4-stroke engine