what does a lightened flywheel do? does it just make it rev out faster or what?

 

frees up more horse power to the wheel

just like.... if your steering wheel weighted 50lbs it'd be harder to steer.

 

rotating mass is reduced=less torque to turn it.

same idea with lighter wheels/tires

 

ok i get it know thanks man

 

Lets your engine rev more freely. You primarily see the effects when up/downshifting, because you can match engine revs much more easily (with a heavier flywheel there's more lag).

Theoretically it lets the car accelerate faster too, though not enough to notice unless you did some drag strip runs before & after. The weight of having to accelerate the whole car while under load is massively greater than the amount of weight in the OEM flywheel vs. a lightened flywheel. When when not under load, such as when rev-matching a shift, the weight of the flywheel is noticeable.

Of course, with a light flywheel, it's much more important to get your revs close when shifting, the flywheel isn't there to smooth out your shifts so the engine gets more abuse. With a heavier flywheel the engine will come to the new rev relatively slowly, whereas with a light flywheel and an idiot driver it can get instantly slammed up/down to speed.

 

and depending on the drivier, the heavier flywheel will launch the car harder (drag racing) therefore more gains than the lightness provided during acceleration.

Anything lighter that 12 lbs for drag racing on NA motor is not needed.......unless your making 250+ whp NA.