The real downside, if you are concerned about
it, is that a LTW flywheel will typically allow gear rattle inside
the trans. One of the purposes of the heavier, or twin mass, flywheel
is that its rotating inertia "absorbs" small changes
in engine RPM. This works in part to effect a change in natural
frequencies which exist in the system. It's sort of a mass damper
if you will. The other part of that is simply the mass.
Another reason is that it allows the vehicle to decelerate at
a slower rate when in a state of engine braking. The intertia
of heavier flywheel works against combustion pressure, less mass
equals more uncountered combustion pressure to slow the engine
and thus the car. A LTW flywheel, especially one with significantly
less mass, will allow the engine to slow quicker, it has less
mass momentum to work with.
For track applications especially, these are of no concern. And
the gear rattle thing will not necessarily occur in all vehicles.
In my first M3 I had the GrpN flywheel and never experienced any
gear rattle. Certainly wear in the transmission will be part of
this equation as well as tolerances of internal parts and such.
Bottom line is that it is unlikely that you will experience any
real negative effects, even an idle issue. What you may notice
initially at idle is more of a lumpiness, the ability of the rotating
inertia to absorb small RPM variations has decreased.
Do it....and if you're going to do it, buy the aluminum 8lb version.
You're in there, you might as well get the bigger change!
Bay Area ///Motorsport
29 January, 2003 12:32