Underdrive pullies

[the_weber]

What is an underdrive pulley? and is a lightweight crank pulley worth it?

[sleepyalero]

An Underdrive pulley refers to an aftermarket crankshaft or accessory pulley (such as an alternator pulley) that is designed to drive a vehicle's accessories at a slower rate than stock. Underdrive in general means the input rate of rotation in a system is greater than the output rate of rotation. However, an underdrive pulley is considered to be an accessory pulley that is larger than the stock pulley, or a crankshaft pulley that is smaller than the stock crankshaft pulley, even though the accessory may not necessarily be underdriven with respect to the crankshaft pulley.

[the_weber]

Originally Posted by sleepyalero

An Underdrive pulley refers to an aftermarket crankshaft or accessory pulley (such as an alternator pulley) that is designed to drive a vehicle's accessories at a slower rate than stock. Underdrive in general means the input rate of rotation in a system is greater than the output rate of rotation. However, an underdrive pulley is considered to be an accessory pulley that is larger than the stock pulley, or a crankshaft pulley that is smaller than the stock crankshaft pulley, even though the accessory may not necessarily be underdriven with respect to the crankshaft pulley.

Had to read that twice to understand it. So an Underdrive light weight pulley that weighs 14 oz. is going to add around 10 HP vs the 4+ lb stock pulley? so worth the $60? yes or am I missing something.

So pull the old pully off put the new one on and bam 10 hp?

[2fst4u]

i have a lightweight underdrive pulley and matching alternator pulley if you'd be interested. throw me a price and i'll let you know. it uses the stock belt. with my supercharger, i don't need it anymore. Let me know

[sleepyalero]

yes its worth it.

[XanderWiFi]

any how to's anywhere to put one of these on?

[Redog]

Lightweight pulleys do not add horsepower, they free up horsepower.

A larger pulley on the alternator is not worth it. It frees up some power, maybe, MAYBE 1 hp, but since is spins the alternator slower, it reduces the amout of charge sent back to the battery and will kill the battery sooner. I had one, and it did just that. For the alternator, I would suggest a lighter pulley. It will free up about 1 maybe 2 hp and will spin the alternator at the same rate.

A lighter crank pulley isn't really worth it IMHO. I had one on my LA1 V6 and it was fine for a few years. Then I must had hit road debis or siomething because it bent, very slightly. Also the aftermarket pulley did not have the crank trigger ring that is required on the V6 motor. The ring was pulled off the old pulley and placed in the new one. I don't know how, this was done back before I did my own work.

Not only was that pulley bent, but the ring was damaged too. The ring ripped my 24x crank sensor in half and I could not drive the car faster than 2000 RPM's without it misfiring. That was about 61 MPH and totally sucked and was dangerous on the PA Turnpike. The speed limit may be 65, but people are going 80.

Now I have a stock crank pulley on and I really don't notice a difference in hp gains or losses. The car is still turning 14's in the 1/4 mile. Maybe about .1 of a second slower, but that's not enough for me to worry about.

I would suggest the lightened alternator pulley. I bought mine from PFYC.com about 5 years ago. They should still have it. It's not in the car right now, but it will go back in one day. it's just not a top proity right now.

If you do decied to do the crank pulley, remove the right front wheel, remove the fender liner, and the crank pulley is right there. Use an impact gun to remove the bolt (don't know the size) then use a "jaw" type tool to remove the pulley from the crank. To reinstall, put the pulley on the crank. put a 2x4 over the pulley, and hit with a hammer until you can start the bolt in the crank snout again, then use the impact to push the pulley on

[the_weber]

Originally Posted by Redog

Lightweight pulleys do not add horsepower, they free up horsepower.

A larger pulley on the alternator is not worth it. It frees up some power, maybe, MAYBE 1 hp, but since is spins the alternator slower, it reduces the amout of charge sent back to the battery and will kill the battery sooner. I had one, and it did just that. For the alternator, I would suggest a lighter pulley. It will free up about 1 maybe 2 hp and will spin the alternator at the same rate.

A lighter crank pulley isn't really worth it IMHO. I had one on my LA1 V6 and it was fine for a few years. Then I must had hit road debis or siomething because it bent, very slightly. Also the aftermarket pulley did not have the crank trigger ring that is required on the V6 motor. The ring was pulled off the old pulley and placed in the new one. I don't know how, this was done back before I did my own work.

Not only was that pulley bent, but the ring was damaged too. The ring ripped my 24x crank sensor in half and I could not drive the car faster than 2000 RPM's without it misfiring. That was about 61 MPH and totally sucked and was dangerous on the PA Turnpike. The speed limit may be 65, but people are going 80.

Now I have a stock crank pulley on and I really don't notice a difference in hp gains or losses. The car is still turning 14's in the 1/4 mile. Maybe about .1 of a second slower, but that's not enough for me to worry about.

I would suggest the lightened alternator pulley. I bought mine from PFYC.com about 5 years ago. They should still have it. It's not in the car right now, but it will go back in one day. it's just not a top proity right now.

If you do decied to do the crank pulley, remove the right front wheel, remove the fender liner, and the crank pulley is right there. Use an impact gun to remove the bolt (don't know the size) then use a "jaw" type tool to remove the pulley from the crank. To reinstall, put the pulley on the crank. put a 2x4 over the pulley, and hit with a hammer until you can start the bolt in the crank snout again, then use the impact to push the pulley on

UI'd be interested in both then. But The site is claiming 2.7 HP freed up for every pound off the crank. If 4 pounds is taken off does it really produce those results or is it

[Redog]

I think that's a bit much, but you should see about 5 to 7

Does it say 10 hp or "up to" 10 hp?

[Oldsman]

i have been running the unorthdox crank pulley for god........years. is it worth it????? by it's self = no. with other mods = yes.

i did a how to for the 2.4 shit years ago and it should still be on here.

[the_weber]

Originally Posted by Redog

I think that's a bit much, but you should see about 5 to 7

Does it say 10 hp or "up to" 10 hp?

just says frees up 2.7 per pound off.