I found an alternator in my garage today that I think I purchased to fit on my first 96V4. It's rated at 70A. I'm now planning to fit it to my 96 project as it will give me more power output should I need it, plus it will simplify the wiring. I think I took this off a Saab 900. My question is, the alternator is Bosch 0120 489 310 311 K1 -14V28 /70A It is fitted with a twin pulley which has a slightly smaller diameter than the original pulley. Should I swap the pulley for the original larger diameter one, or will this give me a reduced output. Or as I assume the 900 would rev even faster can I safely leave it the same diameter. I don't want it to be over revved. Has anyone else here done this conversion?
The idle speed is going to be about the same between a 900 and a 96, but the key dynamic is the ratios between the crank pulley and the other pulleys on the system. You need to keep the ratios about the same as they were on the original car to keep the output at idle right, this is where alternators have the hardest time (I can see the revs dip on my 9-3 when the AC fan kicks in).
If the ratios are kept similar, both cars have similar rev ranges so everything else should work.