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  1. #1
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    Shiv say's Vishnu/FFTEC Single's High-RPM Misfires Solved

    Just stumbled across this on E90Post. This would explain Shiv's absence on the forums. Glad to hear that tmo335tt got his issue fixed, and the other candidates are in the know. I wouldnt have guessed this to be the problem....


    http://www.e90post.com/forums/showth...1#post13147574

    Quote:
    Hi guys,
    In the last few weeks, 3 newly-installed single turbo n54s ran into a high RPM (~6500rpm) misfire problem. One local (tmo335tt) and two in florida. This came as a surprise to us given how many 6MT VFF single turbo cars are running around problem-free. We tried everything from updating DME software, revision CPS algorithms, changing torque limits/calculations in the flash, etc,. Short of disabling misfire detection in our flash (yuck), nothing seemed to solve the problem. We were working with tmo335tt for some time with this and it's a good thing that this problem happened to him because I don't think anyone else would have spent enough time figuring out the cause of the problem. Which he did.

    The problem has to do with the factory dual-mass flywheel that twists at high torque levels. Combine that with high RPM (where misfire diagnostics is most sensitive) and you get a misfire fault without the real misfire. It also explains why the the only three misfiring Single Turbo 6MTs have stock dual-mass flywheels while all others have single mass lightweight flywheels. I also recall BMW themselves changing the clutch/flywheel assembly on the 1M for this reason. And that is only with a small power bump.

    So no, the proper solution isn't to mess with the knock tables or to disable misfire detection (which I did today on tmo335tt's car until his new flywheel comes in next week). The real solution to run a suitable flywheel that is capable of withstanding the higher torque loads that upgraded turbos (and sometimes even stock turbos) are capable of supporting. Other option is to just make less power I suppose.

    Hope that helps those 6MTs (like BigTom, IIRC) that were battling high rpm misfire. And big props for tmo335tt for wrapping his head around this and figuring this out. It will undoubtedly save a lot of people headache in the future as they try to make more and more power.

    Cheers,
    shiv

    P.S. Here is some good info on the subject of dual-mass flywheels and misfire detection:

    http://papers.sae.org/2007-01-3544/

    Shiv

    What do you all think? I think he should offer a deep discount to the single-turbo owners on a new FW. Just my $0.02.

    -Eric
    Click here to enlarge

  2. #2
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    LOL we dont need another one of these threads.

    Theres 20 some pages covering all of that already none of its even proven yet 100%

    //end thread
    - Proven Power Tampa built 6466 ST -
    - N54 6AT WR 711whp 637wtq-
    -N54 WR 1/4mile trap: 133.57mph- -

  3. #3
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    Click here to enlarge Originally Posted by Ak335i Click here to enlarge
    LOL we dont need another one of these threads.

    Theres 20 some pages covering all of that already

    //end thread
    Didnt know that this update was already posted somewhere else. Where?

    Oh, i seee:

    http://www.bimmerboost.com/showthrea...6300rpm/page24

    On the last two page theres been discussion about this. Sorry, i didnt check there first...
    Click here to enlarge

  4. #4
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    Click here to enlarge Originally Posted by Eric335 Click here to enlarge
    Didnt know that this update was already posted somewhere else. Where?
    http://www.bimmerboost.com/showthrea...137#post362137


    Click here to enlarge
    - Proven Power Tampa built 6466 ST -
    - N54 6AT WR 711whp 637wtq-
    -N54 WR 1/4mile trap: 133.57mph- -

  5. #5
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    Check my edit:
    Click here to enlarge Originally Posted by Eric335 Click here to enlarge
    Oh, i seee:

    http://www.bimmerboost.com/showthrea...6300rpm/page24

    On the last two page theres been discussion about this. Sorry, i didnt check there first...
    Okay my bad. @Sticky close this! I thought i was contributing today, damn Click here to enlarge
    Click here to enlarge

  6. #6
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    Click here to enlarge Originally Posted by Eric335 Click here to enlarge
    Check my edit:



    Okay my bad. @Sticky close this! I thought i was contributing today, damn Click here to enlarge
    you done good.. its all good Click here to enlarge
    - Proven Power Tampa built 6466 ST -
    - N54 6AT WR 711whp 637wtq-
    -N54 WR 1/4mile trap: 133.57mph- -

  7. #7
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    WTF have you not been reading the other thread? Closing.

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