I have a 1994 mustang gt. I want to put underdrive pulleys on my 5.0 witch includes a alternator underdrive pulley. Will havinga 200amp alternator power my car better withthe underdrive pulley than the 130 amporwill the 200amp alternator overCHARGE my battery. if a 200 amp is too much power, what amp alternator will best suet my application

 

an alternator will only charge as much as it needs to so no you wont overcharge. However there is no reason for a 200 amp alternator unless you really need it. Also if your worried about the alternator not charging with UDP im sure somone on here will chime in that has them and make you aware of any problems. I have some on my taurus sho, i had problems with 25% reduction pullies but got a set of 15% and they are great.

 

I curse the day i put u/d pullies on.
Nothing but trouble for VERY little return, maybe 2-3hp

I'm about to swap back to standard pullies.

I have a 200amp alternator and it still drops down too
low at idle, just cause its spinng soooo slow

your car will only ask from the alternator what it needs
i have a 150amp fuse on my 200amp alternator cause I know
it will never pull more than that. The difference is in "idle" amps.

stock 75amp makes like 45amps at idle
130amp makes like 65-70amps at idle
200amp makes 100-105 amps at idle
a 130-160amp is more than the car needs..