I just put a march underdrive pulley set on my car, and the belts are real tight, I mean REAL tight, but something is still making a real LOUD hissing anoying Squeaking sound. I put belt dressing on my 2 belts( ac and smog gone) and the noise is sitll there, Its there at low speeds and some idel, REAL LOUD,,i opened my hood and seems to be coming right from my alternatoter it self, should i take the pulley off and try to torque it down or what could it be,
Aj?

 

thats why underdrive pullies are a con game, a little more power at the expense of your accesories.

If the noise from the alt is that loud, it may just plain need replaced. How does the voltage hold up?

 

Its a good alternator i know that. almost new...I dont know whats going on
Aj

 

Bingo! The alternator is an electromechanical load, not a purely mechanical load like the water pump. If the alternator is not spinning fast enough to generate adequately, the regulator will just saturate the field windings more to compensate. And guess what - the crank sheave will see the SAME theoretical load from the alternator - actually a bit more from inefficiencies. Big DUH!

Worse yet, the alternator will be working harder at a lower RPM, which not only means the field will use more current and run hotter, but the cooling fan on the front of the alternator will be turning more slowly so it doesn't cool as effectively. On top of that, the output of the alternator will be more choppy, and less "pure" DC with more voltage spikes. This doesn't help out any of the electronics at all. Didn't anyone ever wonder why the factory designed the belt/sheave ratios to overdrive the alternator in the first place? I don't. More speed actually means less load, since the inefficiencies of the alternator are worst at low RPMs. Hell, the factory went so far as to size down the oil pump gears to minimize load at idle and get the maximum efficiency and fuel mileage. Don't you think they would have taken the same route with the alternator is there was a savings to be realized? They did, by speeding up the alternator, not slowing it down. They also put a larger sheave on the PS pump to load it less. Hello!? Is anyone there?

The best underdrive for a street driven car is a larger water pump sheave, not a smaller crankshaft sheave. The aluminum underdrives should be saved for the track, especially since they wear out so quickly. Then again, if you're that serious, you aren't using belt drives anyway, 'cept for the roots blower....

 

Wow thanks for the input
Aj