How much Horespower is gained by using Aluminum pulleys? Plus how much weight is saved? Has anyone tested the HP gains by reducing rotating mass on an engine dyno? I love the look of the billet pulleys. Just curious.
Yes, they are lighter.... But the HP increase is from the fact they change the diameter of the pulleys vs the stock. They reduced the crank ( or drive) diameter and increased the diameter of the driven pulleys. It slows down your belt speed and driven device speeds, so they don't use as much HP from the engine, giving you a net gain. Does that make sense?o No: That's why they call them under drive pulleys.:bglasses:
if they just weight less, you wont see a h/p gain, but if they are under drive you can see a some h/p gain, they are not worth it to me, because with the waterpump, fan ,and the alternator turning less, you will run hotter and will get less amps out of your alternator, when i tried them my moter ran 20 degrees hotter. in my opion they might give you a better time at the track as long as you still were staying between 170- 190 , thats when a BBB makes the most power. so if you were heating up with the pullys then you would be lossing more power then you gained. i guess they would be good for a race car but not a street car, and if everthing was just right you might get a .05 better E.T. with a moter that was turning over 5000. just my 2 cents Kelly
I found an article somewhere trying out underdrive pulleys and the gains were almost negligible. Maybe on the order of 0.5 or 1 HP. Probably not worth it other than for a cosmetic reason.
A local board member used them on his GS. They would no longer allow the water pump to cool under all conditions so he removed them.
To add to what Jim said, I think there's a posting on here about underdrives only being good if you're running a higher idle or consistent higher RPM's.
