Alternator

Ensure the correct voltage is being sent to/from the alternator, keep you electrical system safe from excessive voltage peaks that could cause damage to sensitive electronics and blow out fuses. Bosch's high quality unit will give you peace of mind knowing the electrical system will be safe and the voltage will remain steady. OEM replacement for BMW part # 12317559183 and 12317501752.

Cars that have oval or D shaped connector use BMW part # 12317515319

Bosch is one of the largest OEM producers of Genuine BMW and aftermarket parts in the world, providing parts for almost every major automotive manufacturer. Bosch has likely supplied many of the original electrical (and mechanical) parts for your BMW. Thanks to their quality, high durability, and reliability, you should expect a long service life from Bosch products.

As a leading source of high performance BMW parts and accessories since 1993, we at Turner Motorsport are honored to be the go-to supplier for tens of thousands of enthusiasts the world over. With over two decades of parts, service, and racing experience under our belt, we provide only quality performance and replacement parts.  All of our performance parts are those we would (and do!) install and run on our own cars, as well as replacement parts that are Genuine BMW or from OEM manufacturers. We only offer parts we know you can trust to perform!

If you own an M57-equipped BMW, you already know this twin-turbo diesel powerplant is an absolute torque monster. What you might also know is that all that low-end grunt and high-compression diesel vibration wreaks absolute havoc on your accessory drive system.

From the factory, both the E90 335d and E70 X5 35d utilize a rigid alternator pulley. With each cylinder's fire, the crankshaft experiences a violent micro-acceleration. Because the alternator has a heavy internal rotor spinning at high speeds, it wants to keep spinning at a constant rate. When the engine suddenly slows down (even minutely between firing cycles), the alternator fights the belt. This constant tug-of-war results in extreme stress on your engine's belt-driven components. At best, it’s an annoying, unrefined chirp at idle; at worst, it’s a ticking time bomb for your expensive harmonic balancer.

To solve this issue, many enthusiasts choose to run a clutched alternator pulley (also called an overrunning alternator pulley). A clutched pulley allows the alternator to "freewheel" or coast when the engine slows down, completely isolating its rotational inertia from the belt drive to prevent component wear. While the N52's clutched pulley (12317560483) is a straight bolt-on, the offset is incorrect for the E90 335d's accessory drive. Thankfully, our engineers designed this zinc-coated spacer to provide the precise amount of spacing needed to perfectly align the new pulley with existing belt drive components.