If you have an Evo 7-8-9 reving past 7000 RPM you are over spinning the factory alternator. Drag racing, or AutoX/track racing that’s going to hurt the alternator and eventually they begin to fail. This alternator pulley is properly designed and underdriven to allow enough alternator RPM to charge at idle and also slow down the alternator at higher RPM greatly prolonging its life span when spinning a 4G63 engine up to 10,500 RPM. Our underdrive alternator pulley will also include a new custom titanium mounting nut.
OEM alternator pulley 7.6 ounce
EvoSpec UD alternator pulley 5.8 ounce
Ti nut .45 ounce
OEM nut .91 ounce
Total ROTATIONAL weight saved 2.26 ounces