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Thread: can't get rid of IPC and surge-mostly stock coyote-dashpot tune

  1. #21
    Advanced Tuner GapRider's Avatar
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    I ended up chasing my tail playing with the ETC tables, got rid of half throttle IPC error but then had IPC elsewhere, couldn't get rid of it in one place without increasing it in other places, whack-a-mole. I put them back to stock and I'll take a stab at adjusting torque tables, wish me luck.
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  2. #22
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    I would go back to focusing more on why your basically stock setup is having error, than trying to find where you can cover it up.

  3. #23
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    Quote Originally Posted by murfie View Post
    I would go back to focusing more on why your basically stock setup is having error, than trying to find where you can cover it up.
    I was thinking about that but wondering what it could be and what to check. All logged items are smooth. The only thing I?ve noticed that I don?t remember from before is the short term fuel trim

  4. #24
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    You have two options to cover it up. Put the error into the MAF curve by lowering the values of lb/min OR make the axis values in your TTL tables so that load values mean less torque by shifting the load values up or the torque values down and recalc the inverse relationship. Either way you are trying to line up desired load and actual load to satisfy the models.

    OR the right way is to find out why your MAF is reading too high it could be dirty, or your O2 sensors are reading too rich, they could be out of calibration to open air oxygen or not maintaining a constant tip temp. Other things less likely, fuel rail pressure could be too high, injectors sticking open, injectors bigger than you actually think, the fuel you are running has a higher than 14.08 stoich. It could be a combo of any of these things.

  5. #25
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    Quote Originally Posted by murfie View Post
    You have two options to cover it up. Put the error into the MAF curve by lowering the values of lb/min OR make the axis values in your TTL tables so that load values mean less torque by shifting the load values up or the torque values down and recalc the inverse relationship. Either way you are trying to line up desired load and actual load to satisfy the models.

    OR the right way is to find out why your MAF is reading too high it could be dirty, or your O2 sensors are reading too rich, they could be out of calibration to open air oxygen or not maintaining a constant tip temp. Other things less likely, fuel rail pressure could be too high, injectors sticking open, injectors bigger than you actually think, the fuel you are running has a higher than 14.08 stoich. It could be a combo of any of these things.
    The O2 sensors (and wiring) are suspect just because they lived through the 2 month transmission swap out but I don't know enough to understand how AFR stuff would cause the ECU to request more air than it verifies it doesn't want? The ECU drives injectors based on MAF, it doesn't drive ETC based on AFR, right?

    I can visually inspect the MAF, O2 sensor wiring and log TPS (I haven't logged the actual TPS).

    One other stab, the 2011 Coyote ETC tables are slightly different so I want to try them. I assume it's the same throttle body?
    Last edited by GapRider; 03-25-2019 at 05:25 AM.
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  6. #26
    Senior Tuner CCS86's Avatar
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    In my experience, the ETC tables are not going to affect your fueling. So, I would look elsewhere.

    The suggestions you already got: MAF sensor condition, O2 sensors / wiring, leaky injectors; are a good place to start.

  7. #27
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    Your both right.

    The error could be put into the MAF or any inferred table related to the fuel system.

  8. #28
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    I plan on putting the laptop down and putting hands and eyes on the car this evening but I'd still like to understand the correlation between o2 sensor(s) lying resulting in too much throttle being commanded?
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  9. #29
    Senior Tuner CCS86's Avatar
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    Quote Originally Posted by GapRider View Post
    I plan on putting the laptop down and putting hands and eyes on the car this evening but I'd still like to understand the correlation between o2 sensor(s) lying resulting in too much throttle being commanded?


    You either have a hardware issue, a fueling calibration issue, an ETC/TQ calibration issue, or some combination of the three.

    When you fueling is so far off, the PCM will struggle to provide consistent power because it's trying to correct the TQ variation of messed up fueling, using the throttle. Only once you fix the fueling, will you see if you also have an ETC issue as well.

  10. #30
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    i didn't find anything loose or suspect with the o2 sensor wiring, throttle looked pretty clean and good, MAF looked clean.

    did a log of all the fuel items i could think of and nothing looked wrong to me, STFT stayed below 10% and LTFT drifted up and down during the drive from 0 to 1.6, then I lost the log because I didn't have it saved when I added another channel to monitor.
    i'll log again tomorrow and post and would be very grateful for help looking at it because the one I saw this evening looked good.
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  11. #31
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    From your 01e23r log.

    You can see its adding fuel when MAP is high vac, then goes normal, then goes rich at a certain point. Where you get surge, fuel trims are great, but its probably not getting all its air through the MAF, or rail pressure is not being controlled correctly from the FPDM. No BAP right?

    01e23r.PNG

    You can setup a similar graph, to get around the averages saying your MAF transfer is good.

  12. #32
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    Quote Originally Posted by murfie View Post
    From your 01e23r log.

    You can see its adding fuel when MAP is high vac, then goes normal, then goes rich at a certain point. Where you get surge, fuel trims are great, but its probably not getting all its air through the MAF, or rail pressure is not being controlled correctly from the FPDM. No BAP right?

    01e23r.PNG

    You can setup a similar graph, to get around the averages saying your MAF transfer is good.
    That histogram looks like it coincides roughly with my MAF error histograms, so that points to a fundamental problem like you guys are saying, right?
    MAF - are you saying if the positives in one area (hi vac /lo load) and the negatives in the (lo vac/hi load) area average each other out, then that means MAF is good?
    I've only seen 'inferred rail pressure', is there another thing I can log to see rail pressure, do I need to hook up an external gauge to verify rail pressure?
    Is BAP 'barometric air pressure'?
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  13. #33
    Senior Tuner CCS86's Avatar
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    BAP: "boost-a-pump", fuel pump voltage booster

  14. #34
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    Quote Originally Posted by CCS86 View Post
    BAP: "boost-a-pump", fuel pump voltage booster
    Thank you
    I did notice the throttle wasn’t completely closed when I inspected last night with key off , should it have been?
    Last edited by GapRider; 03-27-2019 at 12:05 PM.
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  15. #35
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    I made two logs today, one on the way to work this morning and another on the way home this evening - STOCK TUNE

    STFT was about the same for each bank in both logs.
    STFTs were higher this morning > -10, less than 5(-5) on the way home, maybe due to LTFTs adjustment?

    Also, I thought LTFTs took a while to move but they went up and down throughout the drive, should they adjust that quickly?
    You guys have been so much help with this, do the trims look normal?
    LTFTB1-MORNING.JPGLTFTB2-MORNING.JPGSTFTB1-MORNING.JPGSTFTB2-MORNING.JPG
    LTFTB1-EVENING.JPGLTFTB2-EVENING.JPGSTFTB1-EVENING.JPGSTFTB2-EVENING.JPG
    I'll post evening log on the next post
    Attached Files Attached Files
    Last edited by GapRider; 03-27-2019 at 05:37 PM.
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  16. #36
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    evening log
    Attached Files Attached Files
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  17. #37
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    Better numbers, but same over all trend, lean when manifold vacuum is high, rich or normal when it's not. You shouldn't see any patterns in short term trims.

    LTFT will adjust constantly as temps and other environmental factors change constantly. When everything is working properly they are great. When you have an issue they can over correct or under correct. Depending on the KAM cells the problem effects more.

  18. #38
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    Quote Originally Posted by murfie View Post
    Better numbers, but same over all trend, lean when manifold vacuum is high, rich or normal when it's not. You shouldn't see any patterns in short term trims.

    LTFT will adjust constantly as temps and other environmental factors change constantly. When everything is working properly they are great. When you have an issue they can over correct or under correct. Depending on the KAM cells the problem effects more.
    thanks murfie. i'm logging stock tune so the problem has to be hardware then.
    MAF, injectors, throttle, fuel pump, FPDM, o2 sensors

    i read about the coyote mechanical returnless fuel system and learned the FPDM only gives hi/lo to the fuel pump and there's a static regulator @55psi i think. I guess the ECU compensates for varying manifold pressure by referring to the inferred fuel pressure table (which is also stock), is this right?

    high vacuum (lo load) would make it easier to push fuel through the injectors but I'm lean so fuel pressure would be lower than the ECU thinks.
    lo vacuum (hi load) would make it harder to push fuel through the injectors but I'm rich so fuel pressure would be higher than the ECU thinks.
    trying to picture a physical scenario with the pump or FPDM to explain that seems backwards to me.

    i thought TTL>speed density calculated how much fuel should be needed, MAF further adjusts fuel rate and widebands police the show activating STFTs to get desired AFR
    since bank to bank seems equal, that seems to rule out a 'bad' o2 sensor unless they both deteriorated to the same degree and rules out a bad injector(s).

    if MAF had a problem, is it a normal failure mode for it to read too low at low airflow and too high at high airflow?

    the throttle was not fully closed with key off when i inspected it, should it have been?

    i don't know what to do next other than figure out how to measure fuel pressure
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
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  19. #39
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    Yes the FPDM is either at low duty cycle or Hi duty cycle. The threshold is usually around when the MAF reports 11-12lb/min. As seen in the attached image when you filer the graphs by greater than and less than this MAF, it seems to support a weak pump. If the pump is old, it could be weak on the low duty cycle mode causing pressure to be lower than expected and a lean condition. Once it goes to full on mode it has enough life in it to keep up with demand. The pumps are over kill for the fuel demand of the stock engine on E10. They are capable of keeping up with almost twice as much airflow. They are known to get weak over relatively short time periods.

    Almost looks like an IMRC issue, but you don't have those.

    The fuel mass needed is determined by MAF, almost directly, unless MAP from the SD(which is a function of MAF error) corrects the injector PW. TTL values assume the engine is running 1.0 lambda, if it is or not is another function that corrects for estimated engine torque, but you can't go the other away to get fuel with any sort of accuracy.

    A dirty MAF is insulated from the airflow, so it reads lower, producing a leaner than actual result.

    The throttle sitting slightly open is normal.

    Figure out a rail pressure sensor too correct the inferred pressure tables, or replace the fuel pump with a new one. Just be absolutely sure you do not have a small intake manifold leak what so ever, as that will show similar to what you are seeing.

    fuel trims DC filter.PNG
    Last edited by murfie; 03-28-2019 at 02:18 AM.

  20. #40
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    I see what you mean, thanks so much murfie.

    You make me think about the intake leak, especially in light of the 'P0219A and P0219B Fuel Imbalance' code (I don't remember which one) I got a few months back after I'd just replaced the transmission. The code went away and hasn't come back but at the time I noticed LTFT 10% at idle on one side.

    https://forum.hptuners.com/showthrea...hlight=seafoam


    I will look again, really hard for any sign of air leak around the intake manifold.
    We used to spray something flammable like carb cleaner at suspect manifold leak areas at idle and listen for idle speed change, can I still do that safely with these cars (is it 'bad' for the o2 sensors) I know the intake is plastic so I can't completely drench it with this solvent.

    If I can't find anything, I'll try the temporary adjustment of inferred rail pressure to confirm I need a new fuel pump.

    BTW, how did you get your histograms to report those values with my log, it looks like MAX values (my histograms are 'Average' with 5 hits required)
    2019 C7 Stingray M7 - long tube headers, 6.30/6.22 226/238 cam, supporting stuff, DOD and VVT delete.
    Stock everything else