APR's Supercharger Drive and Crank Pulley Upgrades dramatically increase horsepower and torque by increasing the rotational speed of the factory supercharger. APR's Stage II Pulley ECU Upgrade makes the necessary engine management adjustments to handle the increased supercharger speeds, and in turn allows the engine to create more power. The pulleys are sold separately, allowing for multiple levels of performance, each of which builds upon the other. Finally, when combined with APR's Ultracharger Throttle Body Upgrade in a dual pulley setup, the system is alleviated of power robbing inlet restrictions, allowing the engine to achieve exciting new levels of performance! APR's Supercharger Crank Pulley Upgrade increases the diameter of the factory pulley from ~162mm to ~187mm, which in turn spins the supercharger ~15.4% faster. This results in a larger bump in horsepower and torque across the entire RPM range, as the supercharger is spinning at an even higher rate of speed. The pulley retains the factory harmonically balanced crank pulley and bolts on top of the existing unit. It is CNC machined from light weight billet aluminum with weight saving pockets throughout. It has an anodized black finish and includes new crank pulley bolts.