Underdrive Pulley Kit

This kit slows the rotation of the water pump, power steering pump, and alternator, with the goal of returning unused energy to the engine for improved vehicle performance. Constructed from T-6061 aluminum and finished with a durable black hard anodize, these pulleys are built to be stronger and lighter than stock components. The alternator pulley, for example, is less than half the weight of the original steel part, offering superior durability over stock plastic pulleys. The design aims for a subtle, 'stealth' aesthetic that complements the factory look while enhancing performance. Installation is straightforward, typically taking about 1.5 hours with basic hand tools, and requires removal of the fan for access. A new, longer drive belt is included with the kit. Turner Motorsport recommends replacing the separate A/C belt, belt tensioners, and guide/deflection pulleys concurrently for optimal performance and longevity. The kit offers options for the alternator pulley, as BMW vehicles may be equipped with either Bosch or Valeo alternators; the correct pulley must be selected for proper fitment. If unsure, both pulleys can be ordered, with a refund issued for the unused pulley upon its return. For vehicles with significant stereo systems or other battery-draining modifications, a 2-pulley kit option is available that omits the alternator pulley. This kit has been tested for compatibility with factory premium stereo systems. For all stock systems, the 3-pulley set is recommended to maximize power gains and benefit from the lighter alternator pulley. The kit is designed for the 2001-2006 E46 BMW 325i, 325ci, 325xi, 330i, 330ci, and 330xi models with the M54 engine.