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Thread: Stomp or Impact

  1. #1
    Lifetime Member mr.prick's Avatar
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    Default Stomp or Impact

    AFR is rich coming out of PE in the low MAP areas (<40kPa).
    This is only when the throttle is shut quickly,
    if the throttle is steadily reduced AFR is what it should be.
    Will {B3426}_{B3428} or {B3406} correct this?
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  2. #2
    Lifetime Member swingtan's Avatar
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    None of those?

    In the E38, we have

    B2011: Wall Wetting Asymmetry Factor

    Determines the amount of port wall wetting dependent on acceleration or deceleration states.
    Lower number will provide no compensation when deceleration is occurring.

    This has a marked effect on the close throttle rich spike and is what I have used to get rid of it.

    But COS3 doesn't have that particular table so it's going to be a bit tricky. I'd probably try....

    • B3416: Wall Wetting Min TPS: You may be able to set this so that on throttle close it disables dynamics. It may upset the throttle opening though.
    • B3401: Evaporation Time: Given that MAP would be low, you should be able to adjust the evaporation times to help. I'm guessing that a longer evaporation time in the low MAP cells would make the PCM add less fuel on transients as it would think there is more fuel left over from previous injection events.


    But if your dynamics are right for throttle opening, I don't think there is a lot you can do without an asymmetry table like the E38.

    Simon.

  3. #3
    Lifetime Member mr.prick's Avatar
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    Quote Originally Posted by swingtan View Post
    None of those
    After playing around with Impact factor this apparently is the answer because
    I could not see any fueling changes after reducing the values in the lower kPa areas.

    I'll try B3401 and see what happens.
    I am filtering out non PE data and using BEN.
    512k RoadRunner Firmware 12.14R
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  4. #4
    Lifetime Member swingtan's Avatar
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    Does that also alter the "throttle open" fueling? If not it's a good fix!

  5. #5
    Lifetime Member mr.prick's Avatar
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    BENs are slightly lean in throttle tip and the cell count is low
    My WBO2 is a bit far back in the exhaust,
    however I have noticed BENs are near perfect even with MAP increase.
    This leads me to believe that exhaust gas moves fast enough to almost keep up with
    MAP data.

    The few lean cells are not consistently lean they do see rich AFR as well
    just not enough to balance out the lean.
    On a side note: cells in the lower MAP kPa that are rich are also of low cell count.
    but I know they are accurate because they are consistent for log to log.
    Last edited by mr.prick; September 27th, 2009 at 11:55 AM.
    512k RoadRunner Firmware 12.14R
    FlashScan V2 Bootblock V2.07.04 Firmware V2.07.22 EFILive V7.5.7 (Build 191) V8.2.1 (Build 181)
    LC-1 WBO2

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  6. #6
    Lifetime Member mr.prick's Avatar
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    No dice, {B3401} didn't change anything.
    512k RoadRunner Firmware 12.14R
    FlashScan V2 Bootblock V2.07.04 Firmware V2.07.22 EFILive V7.5.7 (Build 191) V8.2.1 (Build 181)
    LC-1 WBO2

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  7. #7
    Lifetime Member mr.prick's Avatar
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    The lean tip in is not so bad when easing into the throttle,
    when the throttle is stomped it is more pronounced.
    AFR richens as TP% decreases slowly or abruptly.

    Click image for larger version. 

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    512k RoadRunner Firmware 12.14R
    FlashScan V2 Bootblock V2.07.04 Firmware V2.07.22 EFILive V7.5.7 (Build 191) V8.2.1 (Build 181)
    LC-1 WBO2

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  8. #8
    Lifetime Member hquick's Avatar
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    For the 'tip-in's'...I found using the 'impact factor modifier' {B9116} table works well.
    Howard

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    IF YOU CAN'T FIX IT WITH A HAMMER, YOU'VE GOT AN ELECTRICAL PROBLEM.


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  9. #9
    Lifetime Member swingtan's Avatar
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    Remember that for tip in, air flow is initially low, therefore the WB AFR will lag a little until airflow pics up. You can see this if you set the stomp setting significantly higher and end up with a rich spike on tip in. If this is done you can see you have commanded too much fuel but it will still lag the commanded AFR in the log.

    The rich AFR on throttle close is what the "asymmetry factor" table fixes in the E38. I'm not sure if any of the table available with the Ls1 controller will help here.

    The final point is possibly being affected by two things...
    1. B3248: Stomp reduction decay rate may be a bit slow to pull back the stomp commanded fuel.
    2. As air flow speed has dropped again, the WB is possibly lagging the commanded and reading the left over rich mixture from PE.

  10. #10
    Lifetime Member mr.prick's Avatar
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    The lean tip in does not worry me so much
    it's the damn throttle slam rich AFR that I want to cure.

    Tip in is less depending on what gear and/or RPM I'm in at the time.
    WBO2 lag is going to be there but looking at my logs
    I can see the lag really is minute.

    IPW drops along with TP% so why would AFR spike so rich when the
    throttle slams shut?
    Maybe injector offsets need to be changed in the low MANVAC areas?

    Any suggestions on how to filter/apply data?
    I made a frame count pid to narrow down the sections with the spikes.
    Click image for larger version. 

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    512k RoadRunner Firmware 12.14R
    FlashScan V2 Bootblock V2.07.04 Firmware V2.07.22 EFILive V7.5.7 (Build 191) V8.2.1 (Build 181)
    LC-1 WBO2

    _________________________________________________

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