Installed an underdrive crank pulley awhile back. Am wondering if I would get better alternator output with an Overdrive Alternator pulley? Trying to make it better for the battery. I have heard that A4 cars really need it, but have not heard much about this on M6 cars. Thanks.

 

I have an SLP Underdrive Pulley on my 2002 M6. Never had an undercharging problem.
Remember, the manual tranny cars are set to idle higher than the A4 cars.

Word on the street has it that you don't have to worry about undercharging unless you are stuck in traffic on a summer night with the A/C, lights, wipers, and a powered subwolfer.