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  1. #1
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    Flywheel timing errors

    Can someone explain this issue of misfires with dual mass flywheel that people are getting? Is this only happening on manual trans cars with upgraded turbos/high horsepower. Is it nothing to worry about unless you have upgraded turbos?

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    Click here to enlarge Originally Posted by nikitino25 Click here to enlarge
    Can someone explain this issue of misfires with dual mass flywheel that people are getting? Is this only happening on manual trans cars with upgraded turbos/high horsepower. Is it nothing to worry about unless you have upgraded turbos?
    In most cases, yes, it is only related to going with aftermarket larger than stock turbos.

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    Click here to enlarge Originally Posted by nikitino25 Click here to enlarge
    Is this only happening on manual trans cars with upgraded turbos/high horsepower.
    As a result of the flywheel issue, yes.

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    oddly, noone has confirmed its the flywheel, as no data has been produced..

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    This actually is new news to me. How would a a flywheel relate to upgraded turbochargers?

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    Click here to enlarge Originally Posted by Ferruccio Click here to enlarge
    This actually is new news to me. How would a a flywheel relate to upgraded turbochargers?
    Supposedly the DMFW causes erratic cps interference
    Click here to enlarge
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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    Supposedly the DMFW causes erratic cps interference
    Sorry, I still don't understand. What is CPS interference and how does that affect timing? I searched the board and couldn't find anything about this.

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    Crank position sensor. The theory is that the DMFW causes the teeth on the reluctor ring to "look" weird to the CPS and it perceives it as a misfire.
    Click here to enlarge
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    Isn't the DMFW a classic insulator surrounded by conductors? At high rpm and high load, it's effectively a capacitor spinning around another stationary piece of metal; possibly inducing a current? Might cause any magnetic-based sensors to go haywire if they aren't filtered properly.

    I haven't played in the hardware game in a while, but I do know from my high-freq PCB design and electromechanical classes that spinning metals paired with insulators can do all kinds of weird things.

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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    oddly, noone has confirmed its the flywheel, as no data has been produced..
    My car hasn't misfired a single time since installing the SMFW. It misfire 100% of the time prior to the SMFW. I'd say that is proof enough.

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    Click here to enlarge Originally Posted by GeorgiaTech335Coupe Click here to enlarge
    My car hasn't misfired a single time since installing the SMFW. It misfire 100% of the time prior to the SMFW. I'd say that is proof enough.
    I'm glad it solved your problems! Have you had a chance to do any vbox runs yet? Either 60-130 or 1/4 mile

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    Click here to enlarge Originally Posted by Sered Click here to enlarge
    Isn't the DMFW a classic insulator surrounded by conductors? At high rpm and high load, it's effectively a capacitor spinning around another stationary piece of metal; possibly inducing a current? Might cause any magnetic-based sensors to go haywire if they aren't filtered properly.

    I haven't played in the hardware game in a while, but I do know from my high-freq PCB design and electromechanical classes that spinning metals paired with insulators can do all kinds of weird things.
    I believe that is the most likely explanation for what is going on.

    What I don't understand is how it's related to HP output. IIRC the misfires were always occurring at around 6200rpms. From my limited understanding of electricity, when generating a current using induction the RPMs and number of windings are pretty much all that matters(assuming everything else stays the same.)
    If it was inducing some sort of electronic interference it should be doing it when the car is stock. Regardless of HP 6200rpms=6200rpms.
    Click here to enlarge
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    Click here to enlarge Originally Posted by bmw335iguy Click here to enlarge
    I'm glad it solved your problems! Have you had a chance to do any vbox runs yet? Either 60-130 or 1/4 mile
    +1 so you're car is running good, lets see some slips!




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    Click here to enlarge Originally Posted by GeorgiaTech335Coupe Click here to enlarge
    My car hasn't misfired a single time since installing the SMFW. It misfire 100% of the time prior to the SMFW. I'd say that is proof enough.
    Click here to enlarge Originally Posted by bmw335iguy Click here to enlarge
    I'm glad it solved your problems! Have you had a chance to do any vbox runs yet? Either 60-130 or 1/4 mile
    yea, its been weeks, nothing new to report? odd. i guess your just too busy out enjoying the car now huh Click here to enlarge

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  16. #16
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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    I believe that is the most likely explanation for what is going on.

    What I don't understand is how it's related to HP output. IIRC the misfires were always occurring at around 6200rpms. From my limited understanding of electricity, when generating a current using induction the RPMs and number of windings are pretty much all that matters(assuming everything else stays the same.)
    If it was inducing some sort of electronic interference it should be doing it when the car is stock. Regardless of HP 6200rpms=6200rpms.
    Maybe load has something to do with it or the stresses induced by load.

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    Click here to enlarge Originally Posted by rader1 Click here to enlarge
    I believe that is the most likely explanation for what is going on.

    What I don't understand is how it's related to HP output. IIRC the misfires were always occurring at around 6200rpms. From my limited understanding of electricity, when generating a current using induction the RPMs and number of windings are pretty much all that matters(assuming everything else stays the same.)
    If it was inducing some sort of electronic interference it should be doing it when the car is stock. Regardless of HP 6200rpms=6200rpms.
    I don't think it has anything to do with a problem in the actual electrical sensing. My theory is that in these cases the flywheel travel was maxed out through the torque peak and somewhere around 6200rpm as the torque fell off it finally began to move away from the travel limit and perhaps there was odd behavior at that time as it started to vibrate against the travel limit.

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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    yea, its been weeks, nothing new to report? odd. i guess your just too busy out enjoying the car now huh Click here to enlarge
    I was in NYC for a week so haven't been able to drive my car. Drag strip is closed for time being. Trying to get down to PBIR this weekend. Been very busy with work and school. Don't get too much time when running an engineering firm and attending law school at night.

    Also still have one issue left to resolve. Car is eating oil badly. Mine seems to be the only one doing it. Did a compression test and leak down and numbers came out fine. Put in the RB PCV valve, but haven't driven it enough to confirm if it fixed the problem. If it doesn't the only thing I can think of is to pull the turbo off, which I REALLY don't want to do as it will take 1-2 days to assemble reassemble.

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    Click here to enlarge Originally Posted by blisstik Click here to enlarge
    Which SMFW did you go with?
    Spec 2+ with AL flywheel.

  20. #20
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    Click here to enlarge Originally Posted by GeorgiaTech335Coupe Click here to enlarge
    I was in NYC for a week so haven't been able to drive my car. Drag strip is closed for time being. Trying to get down to PBIR this weekend. Been very busy with work and school. Don't get too much time when running an engineering firm and attending law school at night.

    Also still have one issue left to resolve. Car is eating oil badly. Mine seems to be the only one doing it. Did a compression test and leak down and numbers came out fine. Put in the RB PCV valve, but haven't driven it enough to confirm if it fixed the problem. If it doesn't the only thing I can think of is to pull the turbo off, which I REALLY don't want to do as it will take 1-2 days to assemble reassemble.
    For starters get an OCC installed on the car. I can't believe FFTEC doesn't include one. At the boost levels you guys run oil has to be flying out of crankcase.
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  21. #21
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    Click here to enlarge Originally Posted by Carl Morris Click here to enlarge
    I don't think it has anything to do with a problem in the actual electrical sensing. My theory is that in these cases the flywheel travel was maxed out through the torque peak and somewhere around 6200rpm as the torque fell off it finally began to move away from the travel limit and perhaps there was odd behavior at that time as it started to vibrate against the travel limit.
    Now that makes sense
    Click here to enlarge
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    Click here to enlarge Originally Posted by Sered Click here to enlarge
    Isn't the DMFW a classic insulator surrounded by conductors? At high rpm and high load, it's effectively a capacitor spinning around another stationary piece of metal; possibly inducing a current? Might cause any magnetic-based sensors to go haywire if they aren't filtered properly.

    I haven't played in the hardware game in a while, but I do know from my high-freq PCB design and electromechanical classes that spinning metals paired with insulators can do all kinds of weird things.
    nah it's not two separately spinning mass, the two masses are joined by springs, so they dampen vibration even better (and shock more importantly), but they both spin at the same rate and position once up to speed.

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    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    nah it's not two separately spinning mass, the two masses are joined by springs, so they dampen vibration even better (and shock more importantly), but they both spin at the same rate and position once up to speed.
    You're misunderstanding what I'm saying; I'm quite aware that its a single spinning mass. It is still two masses separated by an insulator (that's called a capacitor) spinning over a stationary mass (the engine block).

    And the two masses are joined by springs? Not sure I follow you.

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    Click here to enlarge Originally Posted by Flinchy Click here to enlarge
    nah it's not two separately spinning mass, the two masses are joined by springs, so they dampen vibration even better (and shock more importantly), but they both spin at the same rate and position once up to speed.
    Yes with all the associated issues of resonances of coupled spring-mass system, driven by a forcing function with lots of harmonics at firing rate, and then on top of that limited travel of the masses and them maybe bouncing off of each other at max min limits of travel. It is not surprising to me at least that you push HP/TQ more than double stock that such a system begins to get too noisy. Think of 6 hammers pounding twice as hard on a rotating shaft @ 6500 rpm and those poor little coupled dual masses bouncing around, it's going to start getting confusing trying to pull a reliable CPS signal off of it. Also there is a guibo further down the line and it has elastic torsional resonances too. Lot of wiggling going on.

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    I am pretty sure its just the flywheel "bottoming out" at a specific frequency the ECU determines to be a misfire. If you have stock DMFW and 16+ psi of boost with high timing below 3500 you will hear a pretty loud drone at WOT in gears 4-6. I believe this is the DMFW transmitting noise and vibration as its springs are being compressed and decompressed against the excursion limit. Once this limit is hit the two pieces of metal are essentially banging against each other which is then read as a misfire at some rpms. With stock turbos its very rare you will carry that much torque to 5500+ where this happens. On SMF this noise no longer exists since there are no springs to compress (besides the disc). That is my best guess anyway.

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