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Thread: Light flywheels for S54

  1. #1
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    Light flywheels for S54

    I have just finished freshening an S54 that will live in a 2001 E46 Touring. The gearbox will be a ZF320. There are a lot of choices of light flywheels from 10-16 pounds. For non-track use, will 10-11 pound flywheels be too light? I have done these in E36 M3s, one with an M5 clutch kit, and one with a E36 M3 Sachs clutch kit. Both were fine once idle was raised a bit.

    Thoughts?

  2. #2
    Join Date
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    I've daily'd cars with super light flywheels for many many years now. There are no downsides. My current 93 325is has the UUC 8.5lb aluminum flywheel in it with the M5 clutch disc/pressure plate. No issues of any kind, as long as you understand that if you're not competent at driving manual it'll stall at the drop of a hat!

  3. #3
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    Uhh -- I can drive a stick.

  4. #4
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    Wasn't there a discussion years ago that ltw flywheels on S54 were causing premature wear issues? Like even more rod bearing wear, front vibration damper failure, oil pump nut failure etc?

  5. #5
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    Quote Originally Posted by snaponbob View Post
    Uhh -- I can drive a stick.
    That comment wasn't directed at you, but at all the haters that were going to jump in to say light flywheels make the car undrivable in stop and go/daily driving traffic.

  6. #6
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    Quote Originally Posted by jakermac View Post
    That comment wasn't directed at you, but at all the haters that were going to jump in to say light flywheels make the car undrivable in stop and go/daily driving traffic.
    Fair enough. I am running a 97 M3 in SCCA Solo STR, WAS running a 97 328 coupe in STX, and love rowing gears. That said --

    I have had light flywheels in smaller engines, and it was AWFUL !!! Th S54 has a BUNCH of rotating mass, and the pressure plates for these conversions are 2-3 pounds heavier than stock E36 M3, so it should all be good.

  7. #7
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    To me the disadvanteges of light weight flywheel outweight advantage of having one. The most memorable from UUC on s50 that I had was the added noise of the gear box. Rougher running/idling engine. Constant need to make sure you either slam the gears before RMPs drop between shifts or additional revving between shifts...

    And the real world added bonus of ltw flywheel? Miniscule.
    Last edited by bimerok; 11-23-2017 at 01:19 AM.
    - 96 328is 6.0L. (LS1 to LS2 build thread: http://forums.bimmerforums.com/forum...ad.php?2098938)
    - 96 328is 5.7L. (LS1 build thread: http://forums.bimmerforums.com/forum....php?t=1289987)
    - 95 ///M3 6.0L. (LS2 build thread: http://forums.bimmerforums.com/forum....php?t=1619249)

    - 97 ///M3. (e46 Fender Flares/track car build thread: http://forums.bimmerforums.com/forum....php?t=1727098)
    - 96 328is (Dual Fuel Pump to Surge Tank thread: http://www.bimmerforums.com/forum/sh...ad.php?1964025)

  8. #8
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    Quote Originally Posted by bimerok View Post
    To me the disadvanteges of light weight flywheel outweight advantage of having one. The most memorable from UUC on s50 that I had was the added noise of the gear box. Rougher running/idling engine. Constant need to make sure you either slam the gears before RMPs drop between shifts or additional revving between shifts...

    And the real world added bonus of ltw flywheel? Miniscule.
    All that is understood. As it is, the light flywheel PLUS the added weight of the clutch / pressure plate assembly sort of offset each other. I have had M54s apart, and now this S54. NOT the same engines !!! The crankshaft is clearly bigger and therefore heavier, and that adds rotating mass. All that aside, I have installed UUC and JB Racing light flywheels on E36 M3s, and YES, the gearboxes rattled. The fix? Raise the idle speed to 850-900 rpm. Since I will be reflashing the M Touring, the idle will be raised as well.

  9. #9
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    S54/E36,18 Sierra Denali
    I have a uuc 8.5 w/ M5 clutch kit on my S54 E36. Its loud at idle after the car is warm...but the spal and the exhaust aren’t civil either. Car revs fast as shit.

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