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Thread: Engine Starting/Tuning/Troubleshooting Discussion

  1. #1
    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

    -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 )

    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.


    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 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:


    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?

    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:


    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!
    South Dakota State University Alum
    Electrical/Daq/Engine/Drivetrain/Tire guy '09-'14

    Go big, Go blue, Go JACKS!

  2. #2
    Great post! Very useful to those who only know the theory, and don't often have the opportunity to apply it on a dyno (such as myself).

    Only two things I'd like to add:
    1) For troubleshooting - Check the timing. Twice. Then maybe once more. You mentioned it ("base position"), but it is an extremely critical thing to have right, and many people just hook up a timing light and look for a few seconds. Worth your time to check and re check that value. In fact, I think I'll do that again tonight...
    2)Stoichiometric fuel ratio (lambda = 1.0) for gasoline is an air fuel ratio (AFR) of 14.7, not 9.3. I have no idea what it is for E85.
    Owen Thomas
    University of Calgary FSAE, Schulich Racing

  3. #3
    Great post. This is essentially my plan for this year. We already have a base line of sorts and the car starts fairly easily but it has some spots that we really need to fix, mostly fuel and spark timing and the accel/decel compensations.

  4. #4
    Originally posted by Owen Thomas:
    Great post! Very useful to those who only know the theory, and don't often have the opportunity to apply it on a dyno (such as myself).

    Only two things I'd like to add:
    1) For troubleshooting - Check the timing. Twice. Then maybe once more. You mentioned it ("base position"), but it is an extremely critical thing to have right, and many people just hook up a timing light and look for a few seconds. Worth your time to check and re check that value. In fact, I think I'll do that again tonight...
    2)Stoichiometric fuel ratio (lambda = 1.0) for gasoline is an air fuel ratio (AFR) of 14.7, not 9.3. I have no idea what it is for E85.
    i had those flip-flopped HAHAA! knew the numbers sounded right.... doesn't make sense now that i think of it though due to the fact that you'll need about another 30% for ethanol.


    which brings up another point:

    if you're planning on running e85 and are rather new to the whole thing, get the motor so it starts very EASILY on 91/100. Go through the whole process and get the thing running well and then its just a trim to get to e85 (at first anyway)

    if you take the whole map and trim it up by 23%, you'll have a good base point for running e85. Then the starting comps and temp comps will take a little bit of work as well, but it should come easier than trying to start right off of e85.

    I'm going to try and put in some more figures and pictures once i get a change. "A pictures meaning can express ten thousand words" --Chinese proverb
    South Dakota State University Alum
    Electrical/Daq/Engine/Drivetrain/Tire guy '09-'14

    Go big, Go blue, Go JACKS!

  5. #5
    This post is epic. Thank you.

    Ben

  6. #6
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    ^ +1

    I'd just like to add a couple of things from my experience.

    Troubleshooting

    - check compression using a compression tester. If you have a dud ring of some other physical engine problem, it won't run properly (or at all).

    - CRIP: keep in mind that it is possible to set CRIP 180 out. This can be difficult to find, so if you think everything is right but it's still not firing properly, adjust CRIP by 180. We had this fairly often (changing between engines/cams etc.).

    Mapping

    - We have always used Alpha-N tuning, even while turbo'd. A trim table based on manifold pressure gave excellent results. This is also of benefit if you are N/A Alpha-N and make the transition to turbo. Manifold leaks also affect Alpha-N tuning (mainly in a 'weird lambda' sense, which can be a little hard to identify, although often the idle tune will go out the window also).

    Initial tuning

    For Alpha-N tuning, we typically run wideband O2 (after the collector, but sometimes on the individual runners to check cyl trims), manifold pressure/temperature (for trims), oil pressure/temperature, water temp, fuel pressure, and some others I can't think of. Of course, you could run EGT sensors as for the speed-density method.

    With an engine dyno, you can typically set the load from the dyno computer, so you don't need to change gears to achieve different loads. This allows you to ramp at different rates and different throttle positions (effectively = load), or to hold at certain engine speeds for 'spot tuning' (careful with engine temps doing this).

    Ignition tuning - keep in mind that you are aiming for the LEAST possible ignition advance for the most power. This ensures good economy without sacrificing power. Also, for detonation/knock sensing: a metal tube bolted to the block (just below the head) with a tube connected to it and plumbed into a set of earmuffs works a treat.

    Compensations

    Cranking - be sure to have very low ignition advance, or you risk putting too much downwards load on the piston (and the engine won't start).

    Barometric pressure - I've found this isn't necessary when you use a manifold pressure compensation.


    Once again, thanks for the post, it is indeed epic
    Jay

    UoW FSAE '07-'09

  7. #7
    Originally posted by Jay Lawrence:
    ^ +1

    I'd just like to add a couple of things from my experience.

    Troubleshooting

    - check compression using a compression tester. If you have a dud ring of some other physical engine problem, it won't run properly (or at all).

    - CRIP: keep in mind that it is possible to set CRIP 180 out. This can be difficult to find, so if you think everything is right but it's still not firing properly, adjust CRIP by 180. We had this fairly often (changing between engines/cams etc.).
    whenever I've had my CRIP be off on the R6 (180* or otherwise), it tends to poop and fart at me. My mustang on the other hand showed no signs of being 180 off. This is one of those things that I forgot to add in, good catch!


    Mapping

    - We have always used Alpha-N tuning, even while turbo'd. A trim table based on manifold pressure gave excellent results. This is also of benefit if you are N/A Alpha-N and make the transition to turbo. Manifold leaks also affect Alpha-N tuning (mainly in a 'weird lambda' sense, which can be a little hard to identify, although often the idle tune will go out the window also).

    Initial tuning

    For Alpha-N tuning, we typically run wideband O2 (after the collector, but sometimes on the individual runners to check cyl trims), manifold pressure/temperature (for trims), oil pressure/temperature, water temp, fuel pressure, and some others I can't think of. Of course, you could run EGT sensors as for the speed-density method.
    Your maping was one that i was contemplating adding into the original list. I've heard of more and more people tuning alpha-n with a MAP comp in it. From my understanding the MAP comp will account for any pressure fluctuation and the TPS will hold steady base point. I'm really intrigued on this one. Out of curiosity in your MAP comp map (wow...read that again...confusing) is it pressure vs TPS or pressure vs RPM? I'm assuming its the former? Guess I'm having a hard time visualizing that one.

    have you ever compared the EGT's to the lambdas? i thought about this as well but drilling a small hole and clamping on an EGT thermocouple seemed a little easier than welding bungs on...so i took the easy route...hahaa.

    Fuel pressure was the only thing that i didn't consider a "main" sensor that should be monitored already. However, it should be AND its ALSO a great compensation you can add in! Something else i was thinking about adding in I was thinking about monitoring this year. Obviously with a pressure decrease, a given IJPW will flow less, thus needing more fuel to hit the target mixture.

    With an engine dyno, you can typically set the load from the dyno computer, so you don't need to change gears to achieve different loads. This allows you to ramp at different rates and different throttle positions (effectively = load), or to hold at certain engine speeds for 'spot tuning' (careful with engine temps doing this).

    Ignition tuning - keep in mind that you are aiming for the LEAST possible ignition advance for the most power. This ensures good economy without sacrificing power. Also, for detonation/knock sensing: a metal tube bolted to the block (just below the head) with a tube connected to it and plumbed into a set of earmuffs works a treat.
    we have a water brake dyno that (at the time) didn't have the proper gears (driving on the engine and driven on the water brake shaft) on it to put the engine under full load in any given gear....so i shifted gears to get it there! hahahaa. We've got the equipment to make it a little more automated but I need to sit down and spend the time to re-wire it. I've seen some pretty kick ass rigs that will do what you're mentioning though jay. I have found though that tuning over a band will give a good result by averaging out the table values, however given the opportunity to do some spot tuning, i would definitely take advantage of that.

    You also made me think of a rather interesting point. Make your radiator on the dyno HUUUGEEEE. Like, we're running an aluminum radiator out of a bobcat I have to set the fans to kick on around 95*C on the dyno otherwise it has a hard time coming up to operating temp. I'd rather have that problem however than the other way around

    On the timing; what I've always understood is that you'll be able to increase the timing BTDC to a certain point where the torque will peak at a given load point and then it will diminish again. I guess this is what i meant originally so are we talking the same talk just saying it different?? To me it sounds like you're saying the least amount of timing BTDC is the most power, which i don't quite see the reasoning there.

    Compensations

    Cranking - be sure to have very low ignition advance, or you risk putting too much downwards load on the piston (and the engine won't start).

    Barometric pressure - I've found this isn't necessary when you use a manifold pressure compensation.


    Once again, thanks for the post, it is indeed epic
    Retard on crank comp is another one of those that i forgot about. We're running 5*BTDC on the crank comp. As mentioned, too much ign advance will make it harder to start so taking some of that timing out can help out with starting.
    South Dakota State University Alum
    Electrical/Daq/Engine/Drivetrain/Tire guy '09-'14

    Go big, Go blue, Go JACKS!

  8. #8
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    If I remember rightly, the MAP map was 2D (just MAP and IJPW trim). I don't have our engine maps on me at the moment to confirm.

    In the early turbo days we got a decent idea of EGTs by looking at the ones that were glowing vs. those that weren't... We haven't really had proper EGT sensors as far as I know. We typically built a second set of headers to include Lambda tapping points. If you were only going to build one then I imagine the EGT method would be more sensible, although I'd trust straight out Lambda readings more.

    Ahh yes, we have some huge old radiator on ours, and for turbo tuning we had an aftermarket WRX intercooler

    In regards to the timing, I was alluding to the fact that you can hit a deadzone where you've reached MBT and adding another few degrees doesn't have any effect. We would always tune to the lowest advance in this range, or coming back a little bit from it. It ends up a bit safer in terms of detonation (ideal dyno conditions vs. track conditions, for example), and better for economy. But yes, we're on the same page there.
    Jay

    UoW FSAE '07-'09

  9. #9
    Hopefully within another week or so we'll have the intake on the chassis dyno with a different TB. We've got an AT power on it now and we're going to switch over to a jenvy and see where our bands change. I'll post up some Torque plots once we do the runs.


    Another thing that I didn't add into the tuning was close loop lambda control. Typically there's a short trim and a long trim value that are applied to help modify the IJPW based on mixture. There are several options as to when the close loop control is valid but I've generally run it all the time. Its important to only do this once you've had the engine fine tuned on the dyno and had some drive time to adjust out the driving tweaks. The amount of trim available is ~0.3 lambda so if the tune is way off, you'll not be achieving anything with CL. It can however be a great way to help prevent leaning out at high RPMS or overloading while at idle.

    Some parameters that MoTec had that seem to work well for sensor response are 1.5s at low duty and 0.4s high duty. Also the trim step per period shouldn't be larger than 80%. If you do make it larger than that, it can change too fast and cause some overshooting and fluctuation in the lambda that may cause it to get unhappy.
    South Dakota State University Alum
    Electrical/Daq/Engine/Drivetrain/Tire guy '09-'14

    Go big, Go blue, Go JACKS!

  10. #10
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    Excellent post, John. I've got a few things to add.

    The stoichiometric AFR for the E10 gasohol at competition is closer to 14.1:1. Some ECU's might place greater priority on this parameter than others. For E85, it's 9.76:1, but who knows if we'll get E75, E82, or what. It'll be numerically higher than 9.76.

    I liked your idea about cutting injector power while calibrating the cranking PW. To further fine-tune it from there, you'll know it's too much fuel if significant throttle opening helps it start. If it doesn't start regardless of throttle opening, it's too little fuel.

    Teams not running 600/4's will want to exercise extra care when formulating an ignition base map. Check out the chapters on ignition and EFI in A. Graham Bell's "Four Stroke Performance Tuning". Your engine isn't running as restricted as a 600/4 and will not be as tolerant of over-advanced spark timing and lean running at high load. Our single on E85 likes less advance than the stock bike's module gave at "all in".

    Question for you guys: Do you have any rules of thumb for timing the injection event? Our ECU has a nice, big load vs RPM map for the start of injection angle, but it can't be calibrated in real time. Changes must be made offline, a new ECU program must be compiled and flashed--tedious. I can, however change the phase angle of the entire map and it made a significant difference on the engine dyno by shifting trouble spots at various loads to new speeds. I would really prefer a calibratible end of injection angle map.
    -----------------------------------
    Matt Birt
    Engine Calibration and Performance Engineer, Enovation Controls
    Former Powertrain Lead, Kettering University CSC/FSAE team
    1st place Fuel Efficiency 2013 FSAE, FSAE West, Formula North
    1st place overall 2014 Clean Snowmobile Challenge

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