RE: <E36><M3> More Incremental Bang for the Buck

["KOHLBRENNER,MICHAEL (A-Andover,ex1)" <michael_kohlbrenner@xxxxxxxxxxxxxxxxxxx>]

From: "Franklin W. Nelson" <fnelson@domain.elided>

> Regarding lightened flywheels, I'd appreciate it if anyone
> reading this post who has one would give me their comments.

I had one in my old Civic Si, so no direct info in the M3
application, but I do have a few general comments that you
might find useful.  (Flames about mentioning the Civic here
will be cheerfully ignored!)

1. The influence on acceleration of reducing rotating inertia
BEFORE the transmission is greater in 1st gear and diminishes
with every upshift.  In other words, the effect is pretty
evident off the line in 1st, but don't expect a lightened
flywheel to instantly allow you to skip that downshift from
top gear when you really need to blast past someone at
highway speeds.

2. In the Civic, one of the nice parts was the improvement
in engine response while changing gears.  When doing double
clutch downshifts, the engine responded much quicker to
the throttle blip, making shifts a bit quicker.  I can't
say if this will be a significant effect on the M3...

3. Ask your flywheel vendor(s) if they have DynoJet (R) runs
that show the RW HP before and after the lightened flywheel.
Reductions in rotating inertia is one modification that the
DynoJet is perfect for measuring since they themselves are
inertia devices.  Ideally, you'd like to see curves for all
gears both before and after so you can see the decay in
improvement in the higher gears.  Tall order since most
DynoJet runs are at a single gear which is usually one of
the higher ones...

> Moving on to the LSD, I'm not expecting it to be some sort
> of "poor man's supercharger" but the physics make sense to
> me (what little I know of physics).  The higher gear ratio
> will help the car launch more quickly and accelerate more
> quickly in the low rpm ranges.

I think you are confusing two different things.  As long as
you do not break a tire loose, an LSD will make no difference
in acceleration.  What you really seem to be thinking of is
a simple change in final ratio, which may or may not be
associated with an LSD.

Doesn't the M3 already have an LSD?

Regards,
Mike Kohlbrenner
'88 535is

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