GFB 02-10 WRX/STI 2 Piece Under-Drive Pulley Kit w/ Belts (Crank & Alternator)

This Go Fast Bits underdrive pulley kit is made from a single billet of 6061-T6 aluminum, precision CNC machined to exacting tolerances. By significantly reducing the rotating mass of the crank and alternator pulleys, this kit helps your engine feel more lively and willing to rev, offering sharper throttle response and quicker acceleration. Accelerating a heavy factory pulley from 3000-7000 RPM can sap a measurable amount of torque, but GFB's lightweight pulleys reduce inertia by up to 85%, allowing more of that torque to reach the wheels.

In addition to reducing inertia, the underdrive design slows down the accessories like the alternator. This reduces the parasitic load on the engine, especially at higher RPMs, which can provide additional performance benefits. GFB has thoroughly tested these kits to ensure that this improved performance doesn't compromise the function of your driven accessories. This is a bolt-on performance advantage that doesn't require supporting modifications or tuning, and it's designed not to cause engine damage or negative effects on accessory performance.

This kit includes the crank and alternator pulleys along with the necessary belts for installation. It's a well-built component designed to give your Subaru a more responsive feel.