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Thread: STFT Flatlining

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    Question STFT Flatlining

    Failing STFT or it not able to keep up ? This only happens in 4th or 5th gear during post shift. Does too much E85 do this or its just the LPFP getting ready to RIP ? My fuel mixture is about E50-E55, however @BoostAddict found in a ethanol test the Shell stations I frequent have more than 85% ethanol, his test showed something like E90

    If the flatlining is due to too much E85 then I should back off the mix to about E40 then ? Good thing I am running rich as when my trims flat lined my AFRs started to lean out .

    Click here to enlarge

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    Failing STFT or it not able to keep up ? This only happens in 4th or 5th gear during post shift. Does too much E85 do this or its just the LPFP getting ready to RIP ? My fuel mixture is about E50-E55, however @BoostAddict found in a ethanol test the Shell stations I frequent have more than 85% ethanol, his test showed something like E90

    If the flatlining is due to too much E85 then I should back off the mix to about E40 then ? Good thing I am running rich as when my trims flat lined my AFRs started to lean out .

    Click here to enlarge
    I had this issue for a while, drove me nuts. I couldn't find the source of it, and it went away but i don't know exactly what "fixed" it as i changed many things in a short period of time. I did not see any connection to fuel source though. Just be glad that you have a flash tune that allows the DME to see true load. I ran across a few piggy back users that sustained a lean condition for quite some time... resulting in 17:1+ AFR's throughout the pull.

    Here is the thread i created with multiple logs, but unfortunately no answers. http://www.bimmerboost.com/showthrea...MT-logs-please

    If i had to guess what resolved it for me, i would say resetting all fuel adaptations using INPA. My personal opinion is that something is causing the DME to go into open-loop fueling mode.
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    Run on Pump Gas, see if it comes up again. If it runs healthy, try your E85 tune and see if the issue comes back. Confirm by monitoring all your Actual/Target Fuel Pressure numbers and STFT/LTFT.
    COBB AP ProTune by Bren of ///Bren Tuning
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    @benzy89 @lulz_m3

    Well I surely went on an adventure to get this corrected. I cleared all adaptations with INPA no success, lowered Load in the affected RPMs no success, lowered my E85 mix from E50 to E40 no success.

    So I restored my P-Factor values back to its stock values and STFT was restored back to normal. So the P-Factor can cause you to go into open loop ? WOw this is a new one for me, never read anyone experiencing this.

    The only changes I made was in the upper RPMs and reverted it back to stock and it resolved the issue of my stft flatline at post shift

    Click here to enlarge

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    Click here to enlarge Originally Posted by BuraQ Click here to enlarge
    @benzy89 @lulz_m3

    Well I surely went on an adventure to get this corrected. I cleared all adaptations with INPA no success, lowered Load in the affected RPMs no success, lowered my E85 mix from E50 to E40 no success.

    So I restored my P-Factor values back to its stock values and STFT was restored back to normal. So the P-Factor can cause you to go into open loop ? WOw this is a new one for me, never read anyone experiencing this.

    The only changes I made was in the upper RPMs and reverted it back to stock and it resolved the issue of my stft flatline at post shift

    Click here to enlarge
    I really doubt p-factor fixed it. I sent dzenno@ptf some logs earlier this week that flatlined (I haven't seen the issue in awhile). I went back the next day to capture logs with fuel trims and it hasn't happened since. Click here to enlarge
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    Ps. Are you seeing the trims flatline on the 3-4 shift?
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    Click here to enlarge Originally Posted by lulz_m3 Click here to enlarge
    Ps. Are you seeing the trims flatline on the 3-4 shift?
    Yea the log in the OP was starting from 3-5 gears with flatline occurring in 4th and 5th, and the latest log is the same gears. I always log 3-5 gears

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    Click here to enlarge Originally Posted by lulz_m3 Click here to enlarge
    I had this issue for a while, drove me nuts. I couldn't find the source of it, and it went away but i don't know exactly what "fixed" it as i changed many things in a short period of time. I did not see any connection to fuel source though. Just be glad that you have a flash tune that allows the DME to see true load. I ran across a few piggy back users that sustained a lean condition for quite some time... resulting in 17:1+ AFR's throughout the pull.

    Here is the thread i created with multiple logs, but unfortunately no answers. http://www.bimmerboost.com/showthrea...MT-logs-please

    If i had to guess what resolved it for me, i would say resetting all fuel adaptations using INPA. My personal opinion is that something is causing the DME to go into open-loop fueling mode.
    There's an interesting thread on E90 where flash tune pegged STFT due to -LTFT running 17:1+ for half the pull until LTFT came back... no DME reaction, which seems to be typical. If piggy had a lean monitor, which is easy, this would be a good feature.

    OPs issue is 0 trim... basically DME running base map without closed loop adjustments. I've seen it too when my fueling was very rich post shift... tuning adjustments cured it. Guessing DME was thinking O2 not working properly.

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    We need to find/define the VE tables so we don't have to 100% rely on closed loop trim adjustments.

    I mean I absolutely love closed loop WOT adjustments on this car. LOVE THEM. SO MUCH. But, it would be nice to have the open loop dialed in closer too. The ST cars and anyone with a built motor would be really appreciative I bet.

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    Click here to enlarge Originally Posted by JoshBoody Click here to enlarge
    There's an interesting thread on E90 where flash tune pegged STFT due to -LTFT running 17:1+ for half the pull until LTFT came back... no DME reaction, which seems to be typical. If piggy had a lean monitor, which is easy, this would be a good feature.

    OPs issue is 0 trim... basically DME running base map without closed loop adjustments. I've seen it too when my fueling was very rich post shift... tuning adjustments cured it. Guessing DME was thinking O2 not working properly.
    I too thought it might be linked to being rich during the shift, because i was running meth and using NLS which resulted in meth spraying during the shift and the DME seeing a rich condition when it cuts fuel while the clutch is disengaged. I switched to the Cobb OTS s2+Agg map, turned meth off, and it still occured. http://www.datazap.me/u/lulzm3/fuel-...?1-14-19-20-21

    The fact that Buraq is experiencing the issue on a DCT trans just adds to the mystery. He is also not running meth (to my knowledge).
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    Click here to enlarge Originally Posted by V8Bait Click here to enlarge
    We need to find/define the VE tables so we don't have to 100% rely on closed loop trim adjustments.

    I mean I absolutely love closed loop WOT adjustments on this car. LOVE THEM. SO MUCH. But, it would be nice to have the open loop dialed in closer too. The ST cars and anyone with a built motor would be really appreciative I bet.
    You're absolutely right. You can basically use the 3D fuel scalar as a band aid approach, which will get you in the neighborhood, but its not optimal. It's not too big of a deal for those running a flash on stock turbos and probably even stock frame upgrades. But for the piggyback users who aren't letting the DME see true load it gets ugly fast when it goes open loop. Same would be true for the ST guys
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    Click here to enlarge Originally Posted by lulz_m3 Click here to enlarge

    The fact that Buraq is experiencing the issue on a DCT trans just adds to the mystery. He is also not running meth (to my knowledge).

    Nope, no meth here

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