Underdrive Pulley?

Carfreak18 · #1 02-10-2005, 06:55 PM

What exactly is an underdrive pulley?.....Does it have something to do with the belt on the engine?....Sorry if it sounds stupid to most of you.

PoorLuder · #2 02-10-2005, 07:39 PM

Quote:

Originally Posted by Carfreak18

What exactly is an underdrive pulley?.....Does it have something to do with the belt on the engine?....Sorry if it sounds stupid to most of you.

The pulley is what your timing belt (or the serpentine, not certain) runs off of. By lightening the pulley, you recieve gains at the wheels (5-12hp on n/a engines) since it does not take as much effort to move the belts. Underdrive pulleys are smaller than your normal stock pulley. I don't know the specifics but this results in less power to the accesories that your car has (a/c, alternator, and ultimately the battery). For this reason, most people stay away from underdrive pulleys especially if they are running a high powered audio system. Hope that helps. You may want to look into the 3sx lightweight pulley as an alternative to an underdrive pulley. The 3sx one is the same size as the stock one which means that you do not lose charging power and still get decent gains. You can find it at 3sxperformance.com under engine external bolt-ons.

Igovert500 · #3 02-10-2005, 07:55 PM

http://www.pacarsearch.com/stealth/udp.htm

Thourun · #4 02-10-2005, 07:56 PM

I'm pretty shure the light weight does not help with peak horsepower, just with geting the engine moving.

PoorLuder · #5 02-10-2005, 08:08 PM

I read that article but was wondering if what applies to ud pulleys would also apply to the 3sx lightened pulleys? The diagram that was shown made no sense to me (not a mechanic by any stretch of the imagination). Is the harmonic balancer on the pulley itself or something that stabilizes the pulley? Is the size of the udp's the problem or is it a problem since it is not OEM equipment?

Igovert500 · #6 02-10-2005, 08:29 PM

Quote:

Originally Posted by PoorLuder

I read that article but was wondering if what applies to ud pulleys would also apply to the 3sx lightened pulleys? The diagram that was shown made no sense to me (not a mechanic by any stretch of the imagination). Is the harmonic balancer on the pulley itself or something that stabilizes the pulley? Is the size of the udp's the problem or is it a problem since it is not OEM equipment?

The problem is the lack of rubber dampening inserts...which I'm 99% sure (judging by the pics on 3sx) the 3sx pulley lacks just like the UO underdrive pulley. This is just one of those debates that you have to make your own decision. I mean the way I see it, there were 2 major problems with the UO underdrive pulley, it's size and lack of damper...and IMO 3sx did well solving one, but didn't solve the other.

Now it is a debate because nothing has been proven to make one side of the argument more factual than another...so this is a mod you really have to decide on yourself. Personally, I know plenty of people that have run them, even the Underdrive pulleys, and had no problems after 10s of thousands of miles. I also know people that refuse to ever put them on their cars...I prefer to err towards the safe side, as there are plenty of other ways to extract power from a vr4, but to each his own.

PoorLuder · #7 02-10-2005, 08:43 PM

Quote:

Originally Posted by Igovert500

The problem is the lack of rubber dampening inserts...which I'm 99% sure (judging by the pics on 3sx) the 3sx pulley lacks just like the UO underdrive pulley. This is just one of those debates that you have to make your own decision. I mean the way I see it, there were 2 major problems with the UO underdrive pulley, it's size and lack of damper...and IMO 3sx did well solving one, but didn't solve the other.

I guess I will just stick to i/h/e upgrades then... Also, if I had a VR4/TT I would not even concern myself with generating more power. That thing would be enough of a beast for me if it was bone stock. Thanks for clearing everything up.

Stealthee · #8 02-11-2005, 09:52 AM

Honestly a few horror stories scared some people away from ud and lw pulleys. I have many many many more postive results out of having one then people saying they spun a bearing because of one. A friend of mine didnt even know his vr4 had a ud pulley on it till Nov 04. He has owned the car since 02 and put over 15k of abusive miles on it with no problems. The harmonic balancer is does nothing more really than keep the belts quiet. It doesnt have much to do with balancing the internals.

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