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  1. #1
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    Engine going nuts ever since liteweight flywheel

    Recently had a UUC lightweight flywheel with the m3/m5 clutch installed on my 99m coupe. Shortly thereafter, I had engine rev and timing issues, and had to have the vanos unit replaced, chain tensioner replaced, and cam sensor replaced and pulley replaced. Was running fine after that for 2 weeks, and then again today out of nowhere the engine started acting up all of a sudden and now an air mass sensor and crankshaft seņor error codes phase come up with the CEL. Engine ha s no power and the runs like crap - really rough and out of synch. Anyone else ever have any similar problems after installing a lightweight flywheel? Coupe has 66k miles and has never had any engine issues ever -until now... Seems more than coincidental that all of this happens all of a sudden after switching to lightweight flywheel and new clutch. Any possibility the install was screwed up somehow to cause this? Or any other reason?
    Thanks much for any help


  2. #2
    dp
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    changing flywheel mass can introduce issues

    because it can lead to torsional resonance in the crank which could in turn cause all kinds of problems - valve drive, vibration, broken crank, etc.

    without sophisticated and accurate computer modeling and/or testing it's impossible to tell what the exact result of a particular mass may be. it's like a tuning fork. the issue is not that it's lighter, just that it's a specific combination. sounds like the combo you've got is having a problem - the timing chain and vanos are definitely indicators of that. sensor failure may be a result of vibration as well.

    unless you're willing to keep experimenting with different clutch/flywheel combos and/or harmonic damper on the front of the crank you may have to go back to stock. there are aftermarket harmonic dampers you can buy but everything you do with that will be an experiment.


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    Re: changing flywheel mass can introduce issues

    Crap - was afraid of that...
    Thanks much -- greatly appreciated

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    Re: changing flywheel mass can introduce issues

    Right now can drive the car ok, so long as keep the revs below 3500. Anything above that, and it bogs down big time and then goes into limp mode..

    anyone want a 11.5 lb UUC flywheel w/ roughly 500 miles on it?

  5. #5
    dp
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    sounds like a sensor is getting confused

    and/or failing so you'll have to figure out what's wrong regardless, but personally i'd put the stock flywheel back on first.

    messing with things like flywheel, clutch, etc. if fine on a race engine if you don't mind the tinkering and occasionally breaking things. some engines are completely rebuilt after every race and it's considered worthwhile for whatever advantage it gains. however for a street-driven car the pain/reward ratio is rarely favorable.

  6. #6
    dp
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    from the symptoms crank sensor is likely culprit


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    Re: sounds like a sensor is getting confused

    Completely agree. I had the tranny out to do the shift pin fix so took the opportunity to replace clutch too since had to take tranny out anyway. Heard and read many positive opinions on the lighter flywheel setup, so figured would give it a try. Expensive and regrettable decision at this point...
    Thanks again for the insight
    Much appreciated

  8. #8
    CODGER
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    Hmm... Trying to give away trouble? ... ; )

    Pollo,

    Sorry for your troubles, but I couldn't resist cracking wise on your offer to others.

    John
    01' Triple Black MC

  9. #9
    flukecapecod
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    Re: Engine going nuts ever since liteweight flywheel

    when it was running good after the the flywheel did you feel any great improvement?

    How much horspower were you supposed to have gained by doing this swap?

    would'nt putting a supercharger on your Coupe attain even more HP than the route you just took and possibly now would be the time to think of doing it. Do an engine upgrade on heavy duty valve springs to match up to what you want for HP.

    Just my see

  10. #10
    flukecapecod
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    Re: Engine going nuts ever since liteweight flywheel


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