Hey fellas, there is almost NO talk about underdrive pulleys on the whole site. Whats with that?
Are there simply none available? I got this from a 3000GT forum in the US.


UNDER DRIVE PULLEY: This is good for about 8-10Hp at the crank. This has been discussed at length on a lot of different forums. You can listen to people who say its going to break your engine, or you can take a look at others who use them on every car they own. I have yet to hear about anyone spinning a bearing due to the harmonic vibrations. So I always recommend it. Prices range between $50 and $210 depending on your needs.

Any idea if they are the same as the magnas?

are these the same things your refering to ??

http://www.aussiemagna.com/forums/showthread.php?t=41842

not really, thats just standard size but light weight.

im sure underdrive pulleys are a different size altogether, perhaps someone can explain this better?

EDIT: i just confirmed that underdrive pulleys are significantly smaller requiring smaller belts as well.

well did a quick search on the net.

very experience we have with underdriving engine accessories shows that yes underdrive pulleys do deliver more horse power by freeing up power lost to parasitic drag. The amount you will realize depends on your car and the accessories you are driving, a car with alternator, water pump, power steering, A/C and a smog pump will see a larger HP gain then a car with alternator and water pump only.

basically giving less power to the other stuff on your engine ?

well did a quick search on the net.

very experience we have with underdriving engine accessories shows that yes underdrive pulleys do deliver more horse power by freeing up power lost to parasitic drag. The amount you will realize depends on your car and the accessories you are driving, a car with alternator, water pump, power steering, A/C and a smog pump will see a larger HP gain then a car with alternator and water pump only.

basically giving less power to the other stuff on your engine ?


thats correct, i have also found that using an ultra lightweight pulley will do pretty much the same thing without losing power to your accessories.

There is a good write up here and with links to good info.
http://www.3si.org/forum/showthread.php?t=365902&highlight=underdrive+pulleys

They're popular on BA falcons atm, and do provide a tangible gain on those cars (4L na). Wouldn't the motor need to be balanced, yes? I think I'd rather the light weight version - keeps belts and parts easier to remember.