Grimmspeed Lightweight Crank Pulley Blue - Subaru All FA/FB Engines

Your factory crank pulley is responsible for transferring energy from your crankshaft to your water pump, a/c compressor and alternator. It does this by way of a rubber belt and it does it's job well. The drawback to the factory pulley is that it's quite heavy. Reasons for this include less expensive manufacturing and using the pulley's mass to smooth out 'noise' in the accessory system (NOT to be confused with functioning as a harmonic dampener, which it does not). The GrimmSpeed Lightweight Crank Pulley reduces the rotational mass of the system, allowing your engine to accelerate and decelerate the rotating assembly more quickly.