Dinan's lightweight billet aluminum crankshaft pulley underdrives each of the accessories by 13 percent, reducing parasitic drag on the engine for a 6 HP @ 8000 RPM and 4 lb-ft torque @ 8000 RPM gain on a stock vehicle. The Dinan underdrive pulley retains the factory harmonic crankshaft damper, eliminating vibration that might otherwise damage the crankshaft.

The kit includes all of the necessary mounting hardware, a lightweight pulley, and shorter belts. This product is backed by our industry-leading 4-year/50,000 mile warranty so you can rest assured that you are purchasing the best quality product for your BMW.

Features:

• All accessories are underdriven by 13% to decrease drag on the engine.
• Lightweight billet aluminum crankshaft pulley, black anodized and engraved.
• Includes mounting hardware and shorter belts.

For replacement accessory belts, please see the following part numbers:

• Alternator/Water Pump Belt - D561-0006 - ES4715161
• Power Steering/Air Conditioner - D561-0005 - ES4715163