jlangholzj
10-15-2012, 11:35 AM
Seems like this has been a popular problem (for me anyway) with FS/FSAE teams. Its taken me a good couple years to even get comfortable with it and even then there's a few things that I'm always researching or thinking about changing and of course things I just flat out don't know. So I figured that having a healthy discussion about the different types of maping,tuning setups and procedures might be a good way to get juices flowing.
Troubleshooting
---------------
might as well put this first, if you don't have a running engine, the rest is a bit irrelevant isn't it http://fsae.com/groupee_common/emoticons/icon_smile.gif
-check spark. Most ECU's have an option to test the coil outputs. ALSO BE SURE that if your ECU doesn't have built in coil drivers that you're using a CDI or an equivalent coil driver/ignitor box. This can cause major issues. Also be careful on the dwell setting. From what I could figure out, the dwell is how much "charge" to build up before firing the spark. Too much can cause the CDI to get overly hot and not enough can cause a weak spark.
-check injecotrs. Same as the spark. The thing to be sure about with the injectors is that the ECU may or may not have a setting for the injector impedance. Less resistance = more draw.
-sensor voltage. All the sensors getting the allocated 5V? does everything in the ECU make sense. Are all your inputs and outputs reasonable?
AND CHECK CHECK RE-CHECK THE WIRING!!! ...holy cow did i ride the struggle bus on that this last year.
if you're popping out the intake...check the firing order. Same for popping out the exhaust. This is probably switched around. If the firing order is right AND you're running sequential, what MoTec refers to as the "CRIP" or crank index position is likely off. This can be cause for it going boom at the wrong time. Check where your 0*TDC point is with a timing light. This is even a MUST once you get the engine running otherwise this could lead to some bad things happening (Thanks Owen for reminding me of that http://fsae.com/groupee_common/emoticons/icon_smile.gif )
also ABSOLUTELY have a physical ground cable going from the engine to you're battery/ground block. Simply grounding to the frame can cause some stray capacitance with the high-speed nature of the coil firing that can lead to wonky things happeneing
Engine Maping
--------------
To my knowledge the two most popular types of fuel maping are alpha-n and speed density.
what I've picked up is:
alpha-n uses the throttle position to roughly calculate the amount of IJPW (injector pulse width) needed for the given TP (throttle position). This can be beneficial for large duration cams or other engines that have a fluctuating MAP (manifold pressure) that could cause inconsistent or varying IJPW around idle.
speed-density uses the intakes MAP to determine (roughly by volumetric efficiency) the IJPW. This is at an advantage when using forced-induction and other situations where pressure can change.
Currently we run a speed-density setup. I've been thinking of playing around with changing over to alpha-n this winter. I had some problems with getting a consistent idle this year. It wasn't too terrible but it still will fluctuate around 11-1400 when its idling. This might be more of a tuning discussion so I'll leave that for later....
One of the downfalls that I can see to running a speed-density (that I've also experienced) is that if you have any intake leaks, it can lead to obnoxious high-idle. Hopefully there's no leaks to begin with....but I'm curious if alpha-n would be a better approach or not.
Initial tuning
--------------
typically once i get then engine started on the dyno and get everything happy, I'll follow the following order of events for getting a decent "power" maping on the ECU.
Also I prefer to tune off lambda. Or the raw value before AFR is calculated. From my understanding lambda is lambda is lambda no matter what the fuel type. This makes it nice and easy for tuning where no matter what the quality variance, type, etc a given lambda is the same. For example stoic AFR on gasoline is something like 14.7:! where e85 is 9.3:1 (something along those lines anyway). Whereas stoic lambda for both is ~1
before starting, i set a base ignition curve and injection curve. We run a YZF-R6 and the manual states that a general rule of thumb is 10* advance for every 1400??? rpm (I'd have to look to be sure on that number). That gives me a pretty flat curve across the RPM band until I hit full advance around 50*-60*
Some sensors to have for tuning are a wideband O2, cyl head temp, and EGT probes. Also, all these are for a speed-density setup...i expect it to be different for an alpha-n setup.
1)get it running on the dyno
2)set the idle. Get it so it will sit there and not die. Blip the throttle a couple times and make sure it comes back down.
3)set the no-load line. Aka, slowly rev it up and watch the mixture making sure it doesn't go lean. Around 1.2-1.3 lambda is okay yet but max power is typically around .9-1 lambda and i wouldn't want to see much over 1.1 under normal operating conditions.
4)once the no-load line is set I have a LOT better idea of a rough fuel map. Get that guy set a little better before going crazy.
5)with speed-density, applying more load to the engine will cause the load line to shift up on the map (for RPM=x axis and MAP=-y axis) so I'll typically make a pull in each progressive gear watching my lambda for each to get a better fuel map. This will typically take a little longer but it will give more resolution for the map.
this is a rough illustration (don't laugh too hard!) of what would basically happen in a speed-density setup.
http://i260.photobucket.com/albums/ii35/jlangholzj/fuelmap_zpsc550a29b.png
6)just to check everything over I'll put it in the gear we're using the most(2nd or 3rd) and do a pull. IF everything looks good, I'll do a hold at a given RPM and then pull. This will also change the load position and give a little better idea on my maping. BE CAREFUL THOUGH. The reaction of the engine is likely due to acceleration/deceleration compensations.
7)Once the fuel map is looking good, I switch over and tune the ignition curve for peak torque output. This is where it's necisary to have a knock sensor. if not....motor could go boom...or make that nasty knock-a-knock-a-knock sound.
8) once I'm satisfied with the ignition curve, I come back to the fuel map and check everything over and change anything I noticed while changing the ignition map.
9)After all this, I'll monitor the EGT and cyl head temps quite a bit more closely. A cylinder that is more "lean" will typically run hotter. The wideband lambda reading that you're looking at while tuning is an average of all the pistons. By looking at the EGT's and cyl head temps, there canbe some "bank trims" applied to any pistons that may be running leaner (more lean?) than the others. This could be due to a number of things but having even burn across the head is generally a good practice.
After all this....you've got the baseline tune http://fsae.com/groupee_common/emoticons/icon_smile.gif isn't this fun! in reality...aside from getting the engine actually running, getting the initial tune will typically take me an afternoon to do.
If you're wanting to run ethanol (e85) then follow the above tuning procedure only with 91/100 and once you've got a good running engine that starts and is relatively set, trim the whole map up by ~23%. This will get you close for e85. Since all the compensations are acting on top of the IJPW, those should all be okay as well. Some will need some more play but you'll be close!
compensations
-------------
now that I've actually got a running engine, I typically let it cool off an look at all my compensations. Often times endurance can be a killer on getting that engine started again.
Comps I'll typically play with:
eng temp
air temp
battery
starting (cranking)
acceleration
deceleration
barometric pressure
We're running a Motec M84...and they go CRAZY with the amount of adjustments you can put into your compensations but all the above should be available through pretty much any ECU.
eng temp
--------
Typically the injector will fire on the back side of a closed valve for better atomization and also to eliminate any accidental booms going on in the intake. with e85 especially, this can be crucial. Having a colder engine means more fuel is needed to get that sucker at the right temps. To get this one set right it's going to take a little bit...but typically you'll be around operating temp most of the time so I think of it as the "base" for all your other compensations. This one i try and set somewhat early but once the other comps are set, you can come back to it.
air temp
--------
This one takes a little bit of drive time to get set right. Cool mornings or nights as well as hot afternoons to get something thats dialed in right. I'll typically leave this one alone until I'm sure other comps are the problem. Once it gets driving though I'll come back to it.
battery
--------
with additional load on the electrical system (fans, pumps, etc) the voltage drop will cause a change in the EIJPW(effective injector pulse width). This one is typically a percentage and you're able to find it online somewhere or (in my case) you're ECU manufacture will give a good ballpark. IF you don't have this set, you can run into issues once you're fans kick on if you've already got a pretty intensive load on the electrical system.
cranking
--------
By and far the most important comp for having an engine that will consistently and easily start. This typically consists of an initial charge "shot" given to prime it and then a following percentage of additional fuel while cranking. This is typically a eng temp vs crank time map that will change on how warm your engine is. The colder it is, the more fuel you need to add in. again, e85 can be a bit painful here.
One way i like to check this (if I'm having starting issues) is to cut power to the injectors and if it wants to start/sputter after killing the injector power....I know its too rich. The opposite can be said in that if it doesn't want to do anything at all, you may be too lean.
by an large this is one of the compensations that I put the most priority on. I still had a little more playing to do but i almost had it where the car would start heat-soaked or dead cold without touching anything other than the starter button. It's still got a lot of work yet this year...but its close!
Barometric pressure
-------------------
the higher you go up, the thinner the air gets and the less fuel you need to add. This isn't too much of a problem for our applications but non-the-less god to have on there. This is generally a 1-1 relation from what I've seen. Haven't had the chance to play around with this one a whole lot, so if someone could chime in I'd appreciate it.
acceleration/deceleration
-------------------------
this one probably takes me the longest. About the only way to get it set right is with driving, and lots of it. I'll touch on this quick and then combine it into the "drivability" category as well.
so when you accelerate, there's an in-rush of air. This means that you'll need to give it more fuel over a given time to keep it from leaning out. The opposite can be said for deceleration. When you're coming off the throttle there's an abundance of fuel and you'll need to cut some out in order to keep it from either flooding out or staying up in the RPM range.
How the MoTec works is that it will add/take out a given max percentage of fuel for different RPM bands. This is also typically more prevalent in the lower 60-70% of the RPM range and most prevalent in the lower 10-25%. This max percentage is added/subtracted when the throttle is "Stabbed" or if you let off fast. There's also another "Decay" function that changes the amount of that over so many cycles. Aka, you're not going to need to continually add the same amount of fuel, it will be generally less and less over each additional engine cycle. The opposite is also true for decel comps.
here's a plot of what it shouldn't look like:
http://i260.photobucket.com/albums/ii35/jlangholzj/FSAELautox.png
you can see where the lambda (teal trace) is fluctuating with the TPS(blue) on acceleration (rpm is the maroon trace). Where the lambda is initially spiking, thats telling me that I'm straight up leaning out. The fact that it comes back to ~.9 within the gear change also tells me its the accel comp and not something else. Where its leaning/then rich/then lean (kind of a heart-beat looking pulse) I'm assuming my comp isn't quite enough initially (the initial spike) and that i should take away the compensation more gradually to keep it from going rich then lean again. See why this is such a funny deal? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
Ours still isn't quite right....but It's getting there. I'm guessing this will be a bulk of my tuning this year since I've got a decent base map thrown down.
driveability tuning
-------------------
So the engine maping done on the dyno is for "maximum power"...which is all well and good but i bet your drivers will hate you for it. so there's a few things that can be done to improve the "feel" of the engine when driving.
the acceleration and deceleration are big ones. If the decel maping isn't correct, it can cause the driver to feel like the car wants to push them around the corner after getting off the throttle. Also if the acceleration comp isn't right, it may tend to fell sluggish on the throttle.
if it feels sluggish and then all of a sudden "WOW we're WOT!" ...that may also be the acceleration maping OR it could be the timing curve. To put this into perspective, typically I have a bit of a "hole" around idle to keep it idling where i want. if the target RPM is 1k, I'll have 5-10* advance around 1k with a 15* "wall" behind it so that if the RPM drops it will force it to rev up. The same idea can be applied for driving. If the acceleration feel is a little sudden, retarding the timing in the lower ranges of the ign map can be used to help give a little more throttle feel. I've generally found that a large portion of that is with the accel/decel maping though.
here's that little wall i was talking about:
http://i260.photobucket.com/albums/ii35/jlangholzj/ignmap_zps389b0649.png
This is also another area where I'd like to hear some more on.
holy novel of a post....Sorry to do that. I'd like to hear of some other teams tuning procedures and other troubleshooting tips about things that you've encountered in the past. I don't know nearly as much as i should and hopefully this should also alleviate some pains in the early process. Everything I've learned is either self taught or spending time with a tuner and sometimes the latter is hard to come by.
EDIT: added the little bit about tuning for e85 and also added the bit that Owen reminded me about...check yer timing!
Troubleshooting
---------------
might as well put this first, if you don't have a running engine, the rest is a bit irrelevant isn't it http://fsae.com/groupee_common/emoticons/icon_smile.gif
-check spark. Most ECU's have an option to test the coil outputs. ALSO BE SURE that if your ECU doesn't have built in coil drivers that you're using a CDI or an equivalent coil driver/ignitor box. This can cause major issues. Also be careful on the dwell setting. From what I could figure out, the dwell is how much "charge" to build up before firing the spark. Too much can cause the CDI to get overly hot and not enough can cause a weak spark.
-check injecotrs. Same as the spark. The thing to be sure about with the injectors is that the ECU may or may not have a setting for the injector impedance. Less resistance = more draw.
-sensor voltage. All the sensors getting the allocated 5V? does everything in the ECU make sense. Are all your inputs and outputs reasonable?
AND CHECK CHECK RE-CHECK THE WIRING!!! ...holy cow did i ride the struggle bus on that this last year.
if you're popping out the intake...check the firing order. Same for popping out the exhaust. This is probably switched around. If the firing order is right AND you're running sequential, what MoTec refers to as the "CRIP" or crank index position is likely off. This can be cause for it going boom at the wrong time. Check where your 0*TDC point is with a timing light. This is even a MUST once you get the engine running otherwise this could lead to some bad things happening (Thanks Owen for reminding me of that http://fsae.com/groupee_common/emoticons/icon_smile.gif )
also ABSOLUTELY have a physical ground cable going from the engine to you're battery/ground block. Simply grounding to the frame can cause some stray capacitance with the high-speed nature of the coil firing that can lead to wonky things happeneing
Engine Maping
--------------
To my knowledge the two most popular types of fuel maping are alpha-n and speed density.
what I've picked up is:
alpha-n uses the throttle position to roughly calculate the amount of IJPW (injector pulse width) needed for the given TP (throttle position). This can be beneficial for large duration cams or other engines that have a fluctuating MAP (manifold pressure) that could cause inconsistent or varying IJPW around idle.
speed-density uses the intakes MAP to determine (roughly by volumetric efficiency) the IJPW. This is at an advantage when using forced-induction and other situations where pressure can change.
Currently we run a speed-density setup. I've been thinking of playing around with changing over to alpha-n this winter. I had some problems with getting a consistent idle this year. It wasn't too terrible but it still will fluctuate around 11-1400 when its idling. This might be more of a tuning discussion so I'll leave that for later....
One of the downfalls that I can see to running a speed-density (that I've also experienced) is that if you have any intake leaks, it can lead to obnoxious high-idle. Hopefully there's no leaks to begin with....but I'm curious if alpha-n would be a better approach or not.
Initial tuning
--------------
typically once i get then engine started on the dyno and get everything happy, I'll follow the following order of events for getting a decent "power" maping on the ECU.
Also I prefer to tune off lambda. Or the raw value before AFR is calculated. From my understanding lambda is lambda is lambda no matter what the fuel type. This makes it nice and easy for tuning where no matter what the quality variance, type, etc a given lambda is the same. For example stoic AFR on gasoline is something like 14.7:! where e85 is 9.3:1 (something along those lines anyway). Whereas stoic lambda for both is ~1
before starting, i set a base ignition curve and injection curve. We run a YZF-R6 and the manual states that a general rule of thumb is 10* advance for every 1400??? rpm (I'd have to look to be sure on that number). That gives me a pretty flat curve across the RPM band until I hit full advance around 50*-60*
Some sensors to have for tuning are a wideband O2, cyl head temp, and EGT probes. Also, all these are for a speed-density setup...i expect it to be different for an alpha-n setup.
1)get it running on the dyno
2)set the idle. Get it so it will sit there and not die. Blip the throttle a couple times and make sure it comes back down.
3)set the no-load line. Aka, slowly rev it up and watch the mixture making sure it doesn't go lean. Around 1.2-1.3 lambda is okay yet but max power is typically around .9-1 lambda and i wouldn't want to see much over 1.1 under normal operating conditions.
4)once the no-load line is set I have a LOT better idea of a rough fuel map. Get that guy set a little better before going crazy.
5)with speed-density, applying more load to the engine will cause the load line to shift up on the map (for RPM=x axis and MAP=-y axis) so I'll typically make a pull in each progressive gear watching my lambda for each to get a better fuel map. This will typically take a little longer but it will give more resolution for the map.
this is a rough illustration (don't laugh too hard!) of what would basically happen in a speed-density setup.
http://i260.photobucket.com/albums/ii35/jlangholzj/fuelmap_zpsc550a29b.png
6)just to check everything over I'll put it in the gear we're using the most(2nd or 3rd) and do a pull. IF everything looks good, I'll do a hold at a given RPM and then pull. This will also change the load position and give a little better idea on my maping. BE CAREFUL THOUGH. The reaction of the engine is likely due to acceleration/deceleration compensations.
7)Once the fuel map is looking good, I switch over and tune the ignition curve for peak torque output. This is where it's necisary to have a knock sensor. if not....motor could go boom...or make that nasty knock-a-knock-a-knock sound.
8) once I'm satisfied with the ignition curve, I come back to the fuel map and check everything over and change anything I noticed while changing the ignition map.
9)After all this, I'll monitor the EGT and cyl head temps quite a bit more closely. A cylinder that is more "lean" will typically run hotter. The wideband lambda reading that you're looking at while tuning is an average of all the pistons. By looking at the EGT's and cyl head temps, there canbe some "bank trims" applied to any pistons that may be running leaner (more lean?) than the others. This could be due to a number of things but having even burn across the head is generally a good practice.
After all this....you've got the baseline tune http://fsae.com/groupee_common/emoticons/icon_smile.gif isn't this fun! in reality...aside from getting the engine actually running, getting the initial tune will typically take me an afternoon to do.
If you're wanting to run ethanol (e85) then follow the above tuning procedure only with 91/100 and once you've got a good running engine that starts and is relatively set, trim the whole map up by ~23%. This will get you close for e85. Since all the compensations are acting on top of the IJPW, those should all be okay as well. Some will need some more play but you'll be close!
compensations
-------------
now that I've actually got a running engine, I typically let it cool off an look at all my compensations. Often times endurance can be a killer on getting that engine started again.
Comps I'll typically play with:
eng temp
air temp
battery
starting (cranking)
acceleration
deceleration
barometric pressure
We're running a Motec M84...and they go CRAZY with the amount of adjustments you can put into your compensations but all the above should be available through pretty much any ECU.
eng temp
--------
Typically the injector will fire on the back side of a closed valve for better atomization and also to eliminate any accidental booms going on in the intake. with e85 especially, this can be crucial. Having a colder engine means more fuel is needed to get that sucker at the right temps. To get this one set right it's going to take a little bit...but typically you'll be around operating temp most of the time so I think of it as the "base" for all your other compensations. This one i try and set somewhat early but once the other comps are set, you can come back to it.
air temp
--------
This one takes a little bit of drive time to get set right. Cool mornings or nights as well as hot afternoons to get something thats dialed in right. I'll typically leave this one alone until I'm sure other comps are the problem. Once it gets driving though I'll come back to it.
battery
--------
with additional load on the electrical system (fans, pumps, etc) the voltage drop will cause a change in the EIJPW(effective injector pulse width). This one is typically a percentage and you're able to find it online somewhere or (in my case) you're ECU manufacture will give a good ballpark. IF you don't have this set, you can run into issues once you're fans kick on if you've already got a pretty intensive load on the electrical system.
cranking
--------
By and far the most important comp for having an engine that will consistently and easily start. This typically consists of an initial charge "shot" given to prime it and then a following percentage of additional fuel while cranking. This is typically a eng temp vs crank time map that will change on how warm your engine is. The colder it is, the more fuel you need to add in. again, e85 can be a bit painful here.
One way i like to check this (if I'm having starting issues) is to cut power to the injectors and if it wants to start/sputter after killing the injector power....I know its too rich. The opposite can be said in that if it doesn't want to do anything at all, you may be too lean.
by an large this is one of the compensations that I put the most priority on. I still had a little more playing to do but i almost had it where the car would start heat-soaked or dead cold without touching anything other than the starter button. It's still got a lot of work yet this year...but its close!
Barometric pressure
-------------------
the higher you go up, the thinner the air gets and the less fuel you need to add. This isn't too much of a problem for our applications but non-the-less god to have on there. This is generally a 1-1 relation from what I've seen. Haven't had the chance to play around with this one a whole lot, so if someone could chime in I'd appreciate it.
acceleration/deceleration
-------------------------
this one probably takes me the longest. About the only way to get it set right is with driving, and lots of it. I'll touch on this quick and then combine it into the "drivability" category as well.
so when you accelerate, there's an in-rush of air. This means that you'll need to give it more fuel over a given time to keep it from leaning out. The opposite can be said for deceleration. When you're coming off the throttle there's an abundance of fuel and you'll need to cut some out in order to keep it from either flooding out or staying up in the RPM range.
How the MoTec works is that it will add/take out a given max percentage of fuel for different RPM bands. This is also typically more prevalent in the lower 60-70% of the RPM range and most prevalent in the lower 10-25%. This max percentage is added/subtracted when the throttle is "Stabbed" or if you let off fast. There's also another "Decay" function that changes the amount of that over so many cycles. Aka, you're not going to need to continually add the same amount of fuel, it will be generally less and less over each additional engine cycle. The opposite is also true for decel comps.
here's a plot of what it shouldn't look like:
http://i260.photobucket.com/albums/ii35/jlangholzj/FSAELautox.png
you can see where the lambda (teal trace) is fluctuating with the TPS(blue) on acceleration (rpm is the maroon trace). Where the lambda is initially spiking, thats telling me that I'm straight up leaning out. The fact that it comes back to ~.9 within the gear change also tells me its the accel comp and not something else. Where its leaning/then rich/then lean (kind of a heart-beat looking pulse) I'm assuming my comp isn't quite enough initially (the initial spike) and that i should take away the compensation more gradually to keep it from going rich then lean again. See why this is such a funny deal? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
Ours still isn't quite right....but It's getting there. I'm guessing this will be a bulk of my tuning this year since I've got a decent base map thrown down.
driveability tuning
-------------------
So the engine maping done on the dyno is for "maximum power"...which is all well and good but i bet your drivers will hate you for it. so there's a few things that can be done to improve the "feel" of the engine when driving.
the acceleration and deceleration are big ones. If the decel maping isn't correct, it can cause the driver to feel like the car wants to push them around the corner after getting off the throttle. Also if the acceleration comp isn't right, it may tend to fell sluggish on the throttle.
if it feels sluggish and then all of a sudden "WOW we're WOT!" ...that may also be the acceleration maping OR it could be the timing curve. To put this into perspective, typically I have a bit of a "hole" around idle to keep it idling where i want. if the target RPM is 1k, I'll have 5-10* advance around 1k with a 15* "wall" behind it so that if the RPM drops it will force it to rev up. The same idea can be applied for driving. If the acceleration feel is a little sudden, retarding the timing in the lower ranges of the ign map can be used to help give a little more throttle feel. I've generally found that a large portion of that is with the accel/decel maping though.
here's that little wall i was talking about:
http://i260.photobucket.com/albums/ii35/jlangholzj/ignmap_zps389b0649.png
This is also another area where I'd like to hear some more on.
holy novel of a post....Sorry to do that. I'd like to hear of some other teams tuning procedures and other troubleshooting tips about things that you've encountered in the past. I don't know nearly as much as i should and hopefully this should also alleviate some pains in the early process. Everything I've learned is either self taught or spending time with a tuner and sometimes the latter is hard to come by.
EDIT: added the little bit about tuning for e85 and also added the bit that Owen reminded me about...check yer timing!