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  • Track car flywheel choice

    Looking at fitting 0A3 gearbox on track car soon and was thinking about flywheels.
    Car currently has 034 Aluminum flywheel which is around 4.5kg.
    I suspect it maybe the culprit to a stalling issue I have and was thinking to fit a 7A this time round as I have one on the shelf.
    If I was to go 7A is it worthwhile getting skimmed and lightened as I believe its heavier that 3b flywheel?
    Any BTDT

    Thanks
    Steve

  • #2
    Trim the casted bits sticking out on the back of the 7A flywheel, same side as timing pin.
    Especially if you are using a standalone ECU to avoid trigger faults.
    Audi S2 -1994 | 480 Hp 650 Nm | FlexFuel | MaxxECU | 3" Stainless | Porsche GT3 Front Brakes
    http://www.garaget.org/?car=52877

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    • #3
      Nice that should trim a bit of weight off as well, sounds like a good plan.

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      • #4
        I have an o34 billet flywheel in my ur and it also occasionally stalls when slowing down/ braking to standstill. I have a 7a that I've sent to AndyP to get the timing pin welded on and some extra weight machined off
        I was wondering whether the centre could be machined out so that it become like an rr flywheel, has anyone tried this as the needle bearing is in the crank on an ur

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        • #5
          Originally posted by sal_s2 View Post
          I have an o34 billet flywheel in my ur and it also occasionally stalls when slowing down/ braking to standstill.
          Stalling issue is a pain, went through changing ISV, throttle settings and checking vacuum booster trying to find an issue?
          Then remembered I was using 7A flywheel before and suspected the flywheel.

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          • #6
            I’ve machined a few 7A flywheels down, you can take a good chunk off the back which takes them down to the same as a 3B flywheel, which is a nice weight. You can also profile the perimeter around the clutch cover bolts to take a bit more off, but I wouldn’t want to take much more meat out of it really, it’s only cast iron at the end of the day. Also some thermal mass helps on a road driven car where the clutch is slipped
            Panthero Coupé quattro 20vt
            Indigo ABY coupé
            Imola B6 S4 Avant

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            • #7
              What does a 3B flywheel weigh?
              sigpic
              1991 Audi S2 3B - 2.5 Stroker engine
              1997 A6 2.5TDi quattro avant - C4
              1976 RD250E / 350LC cafe racer

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              • #8
                I have around 9kg in my head but it’s been ages since I weighed one
                Panthero Coupé quattro 20vt
                Indigo ABY coupé
                Imola B6 S4 Avant

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                • #9
                  Alex, what do you reckon, can the middle be machined out to become an rr one in your expert opinion?

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                  • #10
                    Billet steel one? There have been a few over the years. 7-8kg and stronger than cast iron.
                    Cheers'en, AndyC
                    1994 ABY Coupe - Projekt Alpinweiss

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                    • #11
                      Originally posted by sal_s2 View Post
                      Alex, what do you reckon, can the middle be machined out to become an rr one in your expert opinion?



                      There is a big ring of material on the back (engine) side which you can machine off, but I don’t this it’s wise to reduce the thickness to less than that of an 3B / RR. Machine from
                      CrMo then the world is your oyster
                      As Andy says, 7-8Kg is the sweet spot for a fast road car with a road clutch you need to slip and nice manners
                      Panthero Coupé quattro 20vt
                      Indigo ABY coupé
                      Imola B6 S4 Avant

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