Do Lightened Flywheels Work?

Installing a lightweight flywheel doesn't decrease torque, but it does decrease inertia, meaning more torque will be needed to break traction with a clutch-kick (drifting or burning out), or to accelerate a vehicle off the line during a launch (drag racing, daily driving).

What are the benefits of a lightened flywheel?

The main advantage to a lower flywheel mass on race cars is that the reduced mass allows the engine to rev more freely. The overall weight loss to the car is really not the key thing, it's letting the engine vary RPM really quickly.

Does lightweight flywheel improve performance?

As a lower mass flywheel spins more freely, the engine will accelerate a bit quicker than normal. The difference isn't large, but the sooner you can get your engine up to the higher RPMs, the more power it can produce. People who track their vehicle will definitely notice an improvement with a lightweight flywheel.