APR Supercharger Drive PulleyAPR'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.