QUOTE(miuk @ Dec 25 2011, 06:18 PM)
Depending on the degree of change (% lighter) compared to stock, there will be % loss in inertial weight which can be beneficial for maintaining engine rev, ie when shifting gears etc. In extreme lightened case where the flywheel and CP is already lightened, it can impact clutch release. Easiest way to put it, faster rise, faster drop.
X % lighter will reduce the moment of inertia by X * r * r %, as I = mr^2.
[I = inertia, m = mass, r = radius]
Therefore, the slight weight reduction of several hundred grams can have a great impact on the Inertia.
In another context, removing the same mass from a larger rotating object reduces the inertia even more.
Example:
removing 200g from a crank pulley (r = 10cm) reduces the inertia by 0.2*0.1*0.1 = -0.002 kgm^2
removing 200g from a flywheel (r = 20cm) reduces the inertia by 0.2*0.2*0.2 = -0.008 kgm^2 = 4 times higher
Impacting clutch release is a bit over exaggerated. All a manual driver need to do is to adapt to the new character of fast rise fast fall. Just shift (clutch-in, shift, clutch-out) faster, so to speak.
A bit tiring isn't it? No more leisure drive? Get a CVT/auto lah then.... Performance modders don't talk about driving comfort.