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  1. #1
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    The mystery of the Fuel trim Flatline... Looking for 6MT logs please.

    Hi guys. I've been playing around with some things lately and really analyzing fuel trims while on meth, not on meth etc. I have noticed a trend... post shift short term fuel trims flat-lining at .22% and the DME appearing to go into Open Loop fueling.

    It doesnt happen consistently, but probably a solid 50% of the time. I have seen this in other users logs as well, but i haven't seen anyone hold a formal discussion.

    Anyone else seeing this issue? Care to share some logs?

    A few basics that i have ruled out;
    Happens on and off meth
    Happens on NLS and regular "quick" shifting



    Here are some logs..

    Cobb OTS S2+Agg map, no meth. http://www.datazap.me/u/lulzm3/fuel-...?1-14-19-20-21


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    Cobb OTS S2+Agg map, with meth. http://www.datazap.me/u/lulzm3/fuel-...-4-14-19-20-21


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    My DD meth map, i think lol. Too many logs to keep track of. http://www.datazap.me/u/lulzm3/fuel-...12-14-19-20-21


    Click here to enlarge


    My Meth Aggressive Map. http://www.datazap.me/u/lulzm3/meth-...-9-19-20-21-22



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  2. #2
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    have seen this in my logs too on occasion but what is it effecting ? afr's still seem fine

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    i had a friend who had this issue, shifting below 6500rpm helped prevent it.... so i guess shifting at or above that.... closer to redline would help cause it. i remember being in his car and doing pulls against him and there was a very obvious bog and he is a good driver and shifts quickly and smoothly. he was running cobb OTS stage 2+

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    Click here to enlarge Originally Posted by cwarren Click here to enlarge
    have seen this in my logs too on occasion but what is it effecting ? afr's still seem fine
    Basically DME stops listening to the Widebands, so depending on how far off your base fuel calculations are - you could be screwed. This is especially bad for piggyback guys where the DME doesn't see true engine load, they go VERY lean.
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  5. #5
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    Click here to enlarge Originally Posted by jeffblue Click here to enlarge
    i had a friend who had this issue, shifting below 6500rpm helped prevent it.... so i guess shifting at or above that.... closer to redline would help cause it. i remember being in his car and doing pulls against him and there was a very obvious bog and he is a good driver and shifts quickly and smoothly. he was running cobb OTS stage 2+
    I've been shifting around 6k exclusively, i'll get some logs shifting earlier and later in the RPM band to see if things change.
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  6. #6
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    The DME cuts fuel during manual trans shifts, similar to how it cuts fuel when decelerating. When fuel is cut fuel trims go to 0 (or 8 in JB4 logs, as we have it scaled differently), and the widebands report 20:1.
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  7. #7
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    Click here to enlarge Originally Posted by Terry@BMS Click here to enlarge
    The DME cuts fuel during manual trans shifts, similar to how it cuts fuel when decelerating. When fuel is cut fuel trims go to 0 (or 8 in JB4 logs, as we have it scaled differently), and the widebands report 20:1.
    Something is causing it to be a sustained, as it doesn't just last during the shift. I'd have to dig but i have even seen logs where the fuel trims flatline at 0 and maintain that during the whole next gear (3rd gear). Terry, do you have any logs of your MT test car rowing through the gears a few times, curious if you are seeing this on JB4 cars. I have seen two other procede cars, actually 3 now, doing this and it isn't pretty when the DME doesn't see actual engine load.
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  8. #8
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    If fuel trims get too far out of whack you can also have a situation where it stays in open loop. This happens with any transmission type. So you'll have to troubleshoot your particular situation.

    I have lots of logs on our E92 but most of them are NLS logs like these. I think we have some logs from the last runway event where the NLS relay was broken so they were all normal shifts. I'll look around for them next time I have the laptop in front of me.
    Attached Images Attached Images   
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    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

  9. #9
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    Here is a normal (no NLS) shift log from one of the runway events.
    Attached Images Attached Images  
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    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

  10. #10
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    @Terry@BMS, The first log you posted appears to have it occur momentarily at the end of the log (whatever gear that is). Are you running meth on this? Is the DME seeing fairly high load?
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  11. #11
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    You mean at the very end when letting off the gas? It's just the normal deceleration fuel cutoff routine. If you're looking for a hard rule on when it cuts fuel or when it kicks over to open loop you'll probably have a hard time determining that. There are several factors involved. If you have a log of a specific issue you're having on a repeatable basis that might be a better approach. But if the logs look like the NLS logs above, that is "normal" behavior for NLS.
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  12. #12
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    Its hard for me to pinpoint the telltale signs i am seeing because of the way your logs are graphed, but these arrows highlight what i am specifically talking about.

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  13. #13
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    That's just a negative fuel trim. 8 is 0 (or open loop), in the logs above.
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    It is the sole responsibility of the purchaser and installer of any BMS part to employ the correct installation techniques required to ensure the proper operation of BMS parts, and BMS disclaims any and all liability for any part failure due to improper installation or use. It is the sole responsibility of the customer to verify that the use of their vehicle and items purchased comply with federal, state and local regulations. BMS claims no legal federal, state or local certification concerning pollution controlled motor vehicles or mandated emissions requirements. BMS products labeled for use only in competition racing vehicles may only be used on competition racing vehicles operated exclusively on a closed course in conjunction with a sanctioned racing event, in accordance with all federal and state laws, and may never be operated on public roads/highways. Please see http://www.burgertuning.com/emissions_info.html for more information on legal requirements related to use of BMS parts.

  14. #14
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    So i tried to capture more logs on the way home from work today, added a few additional parameters that i thought would help me narrow down the culprit. Sure enough, didn't flat line.... SMH.

    http://www.datazap.me/u/lulzm3/meth-...12-15-18-19-22

    http://www.datazap.me/u/lulzm3/meth-...12-15-18-19-22
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  15. #15
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    So is there a remedy for this?

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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by jeffblue Click here to enlarge
    So is there a remedy for this?
    Still trying to isolate what is causing it.
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  17. #17
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    Good work, would love to see a bulletproof solution, happens to my car occasionally.
    Cobb tuned, spec2+, wavetrac, DCI, ARdp's, AA fmic, forge DV's, M3 links & Sways, bbs lm's, bunch of exterior mods, and one happy BMW driver

  18. #18
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    Click here to enlarge Originally Posted by marcvtec Click here to enlarge
    Good work, would love to see a bulletproof solution, happens to my car occasionally.
    Could you reproduce it in a log? If you can, try including fuel mode, ECT, Oil temp & STFT's in the logged parameters.
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    Click here to enlarge Originally Posted by lulz_m3 Click here to enlarge
    Could you reproduce it in a log? If you can, try including fuel mode, ECT, Oil temp & STFT's in the logged parameters.
    hey man I tried to find you some logs with this in them and I have a $#@! ton of logs not one had a prolonged period of flat lined fuel trims . as soon as im back on the throttle it returns to normal even when shifting at high rpm levels and fast . I looked at drag logs and none there either . was pretty sure I had one with this in it but no luck finding it . I don't normally shift into 4th and get on it when logging due to not really wanting to go to jail lol. good luck man love to see what you find out .

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    Has anybody figured out what causes this? Seems like it could be dangerous to the engine. I have the same problem fuel trims stick at 0.2 after a shift and mixture goes lean (high 13's) sometimes bank 2 only then sometimes both banks but never only bank 1. fuel trim seems to kick back in around 5200 rpm's. I have alot of logs on datazap and looked through all of them most of my stage 2+ logs have this issue but only one of my stage 1+ logs, it happened for a very brief time I was running E17 (before i installed downpipes i would use a little e85 in my gas). Now I am afraid to add any e85 to my tank as it my go even more lean when it switches to open loop. Which raises the question is there a way to modify the open-loop map? In the meantime I think I will go back to the 2+ drive map (which i should be using due to timing pulls) and see if this continues. Here are some links to the logs. Any input is appreciated!
    http://www.datazap.me/u/joe86/datalo...9&zoom=245-309
    http://www.datazap.me/u/joe86/datalo...9&zoom=343-550
    http://www.datazap.me/u/joe86/datalo...9&zoom=216-303
    http://www.datazap.me/u/joe86/42815?...9&zoom=396-470
    http://www.datazap.me/u/joe86/chevro...9&zoom=409-484

    stage 1+ e17
    http://www.datazap.me/u/joe86/datalo...6&zoom=139-169
    '08 135i 6MT, IJEOS, cobb v3, vrsf 7" and cp, trbsmrt dv's, vrsf dp's, rb pcv, e85 sensor, cdv delete, swift spec-r, B8, vorschlag plates, alum. subframe mounts, powerflex rsm's, RE bushings, m3 F. con. arms, megan R toe arms, 1M strut brace.

  21. #21
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    Click here to enlarge Originally Posted by joseph Click here to enlarge
    Has anybody figured out what causes this? Seems like it could be dangerous to the engine. I have the same problem fuel trims stick at 0.2 after a shift and mixture goes lean (high 13's) sometimes bank 2 only then sometimes both banks but never only bank 1. fuel trim seems to kick back in around 5200 rpm's. I have alot of logs on datazap and looked through all of them most of my stage 2+ logs have this issue but only one of my stage 1+ logs, it happened for a very brief time I was running E17 (before i installed downpipes i would use a little e85 in my gas). Now I am afraid to add any e85 to my tank as it my go even more lean when it switches to open loop. Which raises the question is there a way to modify the open-loop map? In the meantime I think I will go back to the 2+ drive map (which i should be using due to timing pulls) and see if this continues. Here are some links to the logs. Any input is appreciated!
    http://www.datazap.me/u/joe86/datalo...9&zoom=245-309
    http://www.datazap.me/u/joe86/datalo...9&zoom=343-550
    http://www.datazap.me/u/joe86/datalo...9&zoom=216-303
    http://www.datazap.me/u/joe86/42815?...9&zoom=396-470
    http://www.datazap.me/u/joe86/chevro...9&zoom=409-484

    stage 1+ e17
    http://www.datazap.me/u/joe86/datalo...6&zoom=139-169
    Anyone?

  22. #22
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    1 out of 1 members liked this post. Yes Reputation No
    Ever since I added a back end flash to my car, I haven't had it happen once. My car used to do it almost every fast shift before then.

  23. #23
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    Click here to enlarge Originally Posted by BoostAddict Click here to enlarge
    Ever since I added a back end flash to my car, I haven't had it happen once. My car used to do it almost every fast shift before then.
    Thank you for the reply. So you are using a jb4? Was your backend flash a custom tune?
    '08 135i 6MT, IJEOS, cobb v3, vrsf 7" and cp, trbsmrt dv's, vrsf dp's, rb pcv, e85 sensor, cdv delete, swift spec-r, B8, vorschlag plates, alum. subframe mounts, powerflex rsm's, RE bushings, m3 F. con. arms, megan R toe arms, 1M strut brace.

  24. #24
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    We got this all the time when running out of of fuel while testing the shotguns, we even were getting it consistently testing Stage 3 this last time around when pushing big power. Its extremely dangerous for the motor, the last thing you want it to do is go into open loop when at that time. It would drive our AFR's dangerously lean, and was doing it consistently above 7K as we were trying to spin the new motor to 7500+, we never made it up there because of the Open loop, the car would go lean misfire, and drop me into limp. We would even get it much lower in the rev range if we really ran out of fuel. I have no idea what actually causes it, but it with us it seemed to be directly related to getting near fueling limits, as soon as I put the PI on it went away as it was dumping fuel up top. This has nothing to do with NLS, or shifting we would see it at random RPM's, and on single gear pulls pretty consistently.

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    I switched to the drive map. It is still happening although seems to be less frequent. I forgot to turn off dsc completely and it happened after a major throttle closure caused by traction control. So it seems that it goes into open loop upon throttle closure like it should but something is keeping the dme from re-entering closed loop. I can't find any differences comparing a good log to a bad. I'll go back to stage 1+ map and see if it still happens.
    '08 135i 6MT, IJEOS, cobb v3, vrsf 7" and cp, trbsmrt dv's, vrsf dp's, rb pcv, e85 sensor, cdv delete, swift spec-r, B8, vorschlag plates, alum. subframe mounts, powerflex rsm's, RE bushings, m3 F. con. arms, megan R toe arms, 1M strut brace.

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