Alternator

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.

The alternator in your vehicle keeps the battery at full charge when your engine is running. Because all of your electronic systems run off of this small piece, it's important that it is operational. If your lights are dim while driving or your battery dies within minutes of starting your car, it's time for a new alternator.

This is a NEW alternator from the OEM manufacturer, Valeo. No core charge applies.

The alternator in your vehicle keeps the battery at full charge when your engine is running. Because all of your electronic systems run off of this small piece, it's important that it is operational. If your lights are dim while driving or your battery dies within minutes of starting your car, it's time for a new alternator.

This is a NEW alternator from the OEM manufacturer, Valeo. No core charge applies. Valeo is an OEM manufacturer for many BMW alternators - save money by buying the same alternator in a different box!

The alternator in your vehicle keeps the battery at full charge when your engine is running. Because all of your electronic systems run off of this small piece, it's important that it is operational. If your lights are dim while driving or your battery dies within minutes of starting your car, it's time for a new alternator.

This is a NEW alternator from the OEM manufacturer, Valeo. No core charge applies. Valeo is an OEM manufacturer for many BMW alternators - save money by buying the same alternator in a different box!

The alternator in your vehicle keeps the battery at full charge when your engine is running. Because all of your electronic systems run off of this small piece, it's important that it is operational. If your lights are dim while driving or your battery dies within minutes of starting your car, it's time for a new alternator.

This is a NEW alternator from the OEM manufacturer, Valeo. No core charge applies. Valeo is an OEM manufacturer for many BMW alternators - save money by buying the same alternator in a different box!