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1JZ & 2JZ 6 Rib 10% Underdrive Alternator Pulley
Spinning your alternator passed the factory limit often leads to failure. Extend your alternator’s life by reducing its maximum RPM while maintaining sufficient charge at idle.
Our underdrive alternator pulley will help keep the rpms within a more reasonable range when spinning past the factory limiter. Our pulleys are CNC machined from billet 6061 aluminum and are hard black anodized for a durable finish.
The alternator rotor RPM is not necessarily the same as engine RPM. To calculate the actual alternator RPM, determine the ratio between the two pulley diameters.
Ratio = Crankshaft Pulley Diameter/ Alternator Pulley Diameter
Now that we know the ratio, we can now determine the rotor speed:
Rotor RPM = Pulley Ratio x Engine Speed(example; 2.1 x 870 = 1827 Rotor RPM)
Tech TipGenerally, For drag racing, the alternator should be overdriven by a ratio of 1.75:1 or more. This will allow charging on the return slip and in staging. For street use, we recommend 3:1.