Difference between revisions of "Engine Control"
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| − | + | ==Theory== | |
| + | ===Passive=== | ||
| + | It is possible to run an engine without an engine control module. | ||
| + | Wasted spark such as yamaha wr450 before 2010 | ||
| + | cbr is carb stock | ||
| + | ===Active=== | ||
| + | Parameters that can be independently controlled: | ||
| + | * spark - timing | ||
| + | * fuel - timing, duration (can't really change angle or placement so we can put that under fuel system design, not here) | ||
| + | * air - throttle | ||
| + | * temperature - radiator redirect valve, fan control | ||
| + | * valve timing, valve lift (not electronically tunable, but still control, i'd be willing to put this under intake if that's a better place) | ||
| − | |||
| + | Engine control is the most common way to implement [[Traction Control]] in an FSAE environment | ||
| + | ==Tuning== | ||
| + | Engine tuning is the idea of changing the inputs to the engine to achieve a desired goal. <span>Usually this goal is peak engine torque at every operating condition.</span>The engine will have to operate under a wide range of conditions. The two independent variables that are used to map the driving conditions are (1) Load and (2) RPM. Among the many knobs that can change how the engine performs are two factors that have outsized effects: how much gas to burn at a time and when in the engine cycle to burn it. In modern engines, the amount of fuel used at one time is most easily and finely controlled by changing how long the fuel injector is open. When the fuel is ignited can easily and finely be controlled by changing when the sparkplug is triggered.<span>The spark timing and fuel duration will each form a 3D surface when plotted against speed and load. (pic)</span> | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ||
| − | + | ===Engine Control Strategies=== | |
| − | + | ====Alpha-n==== | |
| − | = | + | The most common engine control strategy (at least in fsae, not sure about the galaxy brains across the pond) is alpha-n. <br />Alpha-n tune uses the throttle position angle (<math> \alpha </math> ) to approximate engine load. Use of throttle position to approximate engine load requires ("""""requires""""" we all know most of us dont do this as much as we should lol) compensation for barometric pressure changes. There is really a continuity between using throttle position exclusively and MAP exclusively for engine control.<br /> |
| − | == | + | =====Advantages===== |
| − | + | This is a direct interpretation of what the driver wants. WOT? You are getting a lot of gas. Idle position? You aren't getting any gas. | |
| − | + | =====Drawbacks===== | |
| − | + | This is throttle body dependent: change how your throttle is setup and your map is basically bunk unless you spend a lot of time getting it aligned with what you had. | |
| − | == | + | ====Speed-Density==== |
| − | + | Speed-density tuning uses the manifold absolute pressure (air density) to measure engine load. | |
| − | control | + | =====Advantages===== |
| − | + | =====Drawbacks===== | |
| − | + | ====MAF Control==== | |
| − | + | Not sure if there's a fancy name for maf control, not sure if anyone uses it either. | |
| − | = | + | =====Advantages===== |
| − | + | =====Drawbacks===== | |
| − | + | ==Theory== | |
| − | + | ===Dithering=== | |
| − | + | need to make this clearer | |
| − | Not sure if there's a fancy name for maf control, not sure if anyone uses it either. | + | Since the engine torque output is a non-linear function of many variables, and the resultant surface isn't analytically determinate, the torque surface is navigated by dithering. This involves running the engine on a dynamometer and, for each engine control variable, taking small steps in a direction and determining the effect the small step has on the torque. If the result is a decrease in torque, another direction is pursed. By chasing the direction of increasing torque for every operating condition, the engine control is optimized. this is just one big gradient ascent, but very badass. |
| − | ==Theory | + | ===Open vs. Closed Loop Tuning=== |
| − | + | open loop tuning is doing it yourself, run the engine and check the outputs. closed loop tuning is usually done to a specific lambda and is handled by the ECM. Closed loop control can be very powerful, but suffers in throttle transients, which is where FS cars spend a lot of time. Open loop control is an explicit formulation for fuel and spark based on throttle position, MAP, and pretty much everything besides Lambda. One dyno guy I talked to said that his drag cars run in open loop all the time. Correspondence with the ECU OEM I was working with noted that open loop is the first thing you should get down, and closed loop can do the last bit of engine fine control. | |
| − | need to make this clearer | + | ===Dynamometer=== |
| − | Since the engine torque output is a non-linear function of many variables, and the resultant surface isn't analytically determinate, the torque surface is navigated by dithering. This involves running the engine on a dynamometer and, for each engine control variable, taking small steps in a direction and determining the effect the small step has on the torque. If the result is a decrease in torque, another direction is pursed. By chasing the direction of increasing torque for every operating condition, the engine control is optimized. this is just one big gradient ascent, but very badass. | + | see [[:System Testing]] |
| − | + | ||
| − | open loop tuning is doing it yourself, run the engine and check the outputs. closed loop tuning is usually done to a specific lambda and is handled by the ECM. | + | should have its own page also |
| − | + | ===Spark Tuning=== | |
| − | == | + | |
| − | *mbt | + | * mbt |
[diagram of spark timing on torque] | [diagram of spark timing on torque] | ||
| − | == | + | * Knock is typically not an issue with a stock 4cyl. Not sure how to convey in 10 years of this I have never seen or heard evidence of it. |
| − | *duration | + | |
| − | **lbt | + | ===Fuel Tuning=== |
| − | *timing | + | |
| − | ==Tuning | + | * duration |
| − | == | + | ** lbt |
| − | == | + | * timing |
| + | |||
| + | ===Tuning for Startup=== | ||
| + | give it a little gaz to get 'er going | ||
| + | ===Tuning for Idle=== | ||
| + | |||
| + | * Run lean, at least in the case of the 4cyls they do not seem to mind being 15+ [citation needed]<br /> | ||
| + | * Stock CBR idles at ~900RPM, rare that fsae cars run that low. In my experience anything below 2KRPM is a victory. [citation needed] | ||
| + | * Idle air controllers are huge for accurate idle control. [citation needed] | ||
| + | * Sharp pickup on throttle tip-in | ||
| + | * limited spark advance - dont want engine to pick up, keep it stable | ||
| + | * "torque well" | ||
| + | * efficiency - don't waste gas | ||
| + | * idle noise limit | ||
| + | |||
| + | ===Tuning For Quick Rev=== | ||
| + | ==Closed v open loop engine control== | ||
| + | |||
| + | * short term factors | ||
| + | * long term factors | ||
| + | * place in motorsport | ||
| + | |||
| + | =Data and Data Collection= | ||
| + | [link to daq and electronics] | ||
| + | ==Data used to run the engine== | ||
| + | (please someone come up with a better title for this section - simon)<br />(needed if not running wasted spark) | ||
| + | * cam sync sensor is needed to determine crank/valve angle - fire spark and fuel on every other rotation | ||
| + | * determine place on fuel/spark map | ||
| + | ** load (alpha, map, maf) | ||
| + | ** rpm | ||
| + | |||
| + | ==Compensations== | ||
| + | |||
| + | * IAT - cooler air is denser and allows for more fuel burn, denser charge may need different spark advance | ||
| + | * map (for alpha-n) - map allows for delays b/w throttle actuation and change in how much air is in intake system, esp with larger plenums, or extreme throttle changes (dump for accel, or complete lift-off) | ||
| + | * coolant temp - warm engine runs more better (afaik fuel vaporization and i know there's other stuff i dont know) but not too hot, can tune to dump fuel to cool engine if its close to overheating though not | ||
| + | * TPS rate compensation for slamming or lift-offs | ||
| + | recommended bc its not efficient | ||
| + | |||
| + | ==stuff you should get so you can figure out wth ur doing== | ||
| + | (safety stuff?) | ||
| + | * oil pressure - low op means stop. The relationship between RPM and oil pressure is linear and if it falls off, you are in deep trouble or will be very soon.<br /> | ||
| + | * coolant temp - if its boiling, stop, regulation calls for water which boils at 212 (at normal altitudes @colorado) | ||
| + | |||
| + | ==cool data so you can do custom engine stuff== | ||
| − | + | * cylinder pressure | |
| − | + | * knock sensor (cyl pressure can handle this if you have it) | |
| − | + | * fuel flow meter | |
| − | + | * cyl temperature | |
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I'm sure there's stuff im forgetting | I'm sure there's stuff im forgetting | ||
| + | [[Category:Internal Combustion]] | ||
Latest revision as of 10:07, 30 March 2022
Theory
Passive
It is possible to run an engine without an engine control module. Wasted spark such as yamaha wr450 before 2010 cbr is carb stock
Active
Parameters that can be independently controlled:
- spark - timing
- fuel - timing, duration (can't really change angle or placement so we can put that under fuel system design, not here)
- air - throttle
- temperature - radiator redirect valve, fan control
- valve timing, valve lift (not electronically tunable, but still control, i'd be willing to put this under intake if that's a better place)
Engine control is the most common way to implement Traction Control in an FSAE environment
Tuning
Engine tuning is the idea of changing the inputs to the engine to achieve a desired goal. Usually this goal is peak engine torque at every operating condition.The engine will have to operate under a wide range of conditions. The two independent variables that are used to map the driving conditions are (1) Load and (2) RPM. Among the many knobs that can change how the engine performs are two factors that have outsized effects: how much gas to burn at a time and when in the engine cycle to burn it. In modern engines, the amount of fuel used at one time is most easily and finely controlled by changing how long the fuel injector is open. When the fuel is ignited can easily and finely be controlled by changing when the sparkplug is triggered.The spark timing and fuel duration will each form a 3D surface when plotted against speed and load. (pic)
Engine Control Strategies
Alpha-n
The most common engine control strategy (at least in fsae, not sure about the galaxy brains across the pond) is alpha-n.
Alpha-n tune uses the throttle position angle ( ) to approximate engine load. Use of throttle position to approximate engine load requires ("""""requires""""" we all know most of us dont do this as much as we should lol) compensation for barometric pressure changes. There is really a continuity between using throttle position exclusively and MAP exclusively for engine control.
Advantages
This is a direct interpretation of what the driver wants. WOT? You are getting a lot of gas. Idle position? You aren't getting any gas.
Drawbacks
This is throttle body dependent: change how your throttle is setup and your map is basically bunk unless you spend a lot of time getting it aligned with what you had.
Speed-Density
Speed-density tuning uses the manifold absolute pressure (air density) to measure engine load.
Advantages
Drawbacks
MAF Control
Not sure if there's a fancy name for maf control, not sure if anyone uses it either.
Advantages
Drawbacks
Theory
Dithering
need to make this clearer Since the engine torque output is a non-linear function of many variables, and the resultant surface isn't analytically determinate, the torque surface is navigated by dithering. This involves running the engine on a dynamometer and, for each engine control variable, taking small steps in a direction and determining the effect the small step has on the torque. If the result is a decrease in torque, another direction is pursed. By chasing the direction of increasing torque for every operating condition, the engine control is optimized. this is just one big gradient ascent, but very badass.
Open vs. Closed Loop Tuning
open loop tuning is doing it yourself, run the engine and check the outputs. closed loop tuning is usually done to a specific lambda and is handled by the ECM. Closed loop control can be very powerful, but suffers in throttle transients, which is where FS cars spend a lot of time. Open loop control is an explicit formulation for fuel and spark based on throttle position, MAP, and pretty much everything besides Lambda. One dyno guy I talked to said that his drag cars run in open loop all the time. Correspondence with the ECU OEM I was working with noted that open loop is the first thing you should get down, and closed loop can do the last bit of engine fine control.
Dynamometer
see System Testing
should have its own page also
Spark Tuning
- mbt
[diagram of spark timing on torque]
- Knock is typically not an issue with a stock 4cyl. Not sure how to convey in 10 years of this I have never seen or heard evidence of it.
Fuel Tuning
- duration
- lbt
- timing
Tuning for Startup
give it a little gaz to get 'er going
Tuning for Idle
- Run lean, at least in the case of the 4cyls they do not seem to mind being 15+ [citation needed]
- Stock CBR idles at ~900RPM, rare that fsae cars run that low. In my experience anything below 2KRPM is a victory. [citation needed]
- Idle air controllers are huge for accurate idle control. [citation needed]
- Sharp pickup on throttle tip-in
- limited spark advance - dont want engine to pick up, keep it stable
- "torque well"
- efficiency - don't waste gas
- idle noise limit
Tuning For Quick Rev
Closed v open loop engine control
- short term factors
- long term factors
- place in motorsport
Data and Data Collection
[link to daq and electronics]
Data used to run the engine
(please someone come up with a better title for this section - simon)
(needed if not running wasted spark)
- cam sync sensor is needed to determine crank/valve angle - fire spark and fuel on every other rotation
- determine place on fuel/spark map
- load (alpha, map, maf)
- rpm
Compensations
- IAT - cooler air is denser and allows for more fuel burn, denser charge may need different spark advance
- map (for alpha-n) - map allows for delays b/w throttle actuation and change in how much air is in intake system, esp with larger plenums, or extreme throttle changes (dump for accel, or complete lift-off)
- coolant temp - warm engine runs more better (afaik fuel vaporization and i know there's other stuff i dont know) but not too hot, can tune to dump fuel to cool engine if its close to overheating though not
- TPS rate compensation for slamming or lift-offs
recommended bc its not efficient
stuff you should get so you can figure out wth ur doing
(safety stuff?)
- oil pressure - low op means stop. The relationship between RPM and oil pressure is linear and if it falls off, you are in deep trouble or will be very soon.
- coolant temp - if its boiling, stop, regulation calls for water which boils at 212 (at normal altitudes @colorado)
cool data so you can do custom engine stuff
- cylinder pressure
- knock sensor (cyl pressure can handle this if you have it)
- fuel flow meter
- cyl temperature
I'm sure there's stuff im forgetting
