UR Underdrive Pulley

Post by **jpalm** » Wed Nov 13, 2002 2:59 pm

Before I fork out $200 in a Group Buy for this pulley on a Spec V I wanted to get some feedback on whether there is any drawback to this. I know that it gives something in the range of 7HP due to reducing parisitic loss but does it effect anything negatively (ie. running accessories...my stereo is the RF stock system).

I'm kinda new to tuning (at 31!) but I want to keep this car as a project tuner.

Also is this basically a easy installation? I believe that I have all the tools necessary.

Thanks for your input!

Post by **johnsharpe** » Wed Nov 13, 2002 2:59 pm

Friends have done this on various Mustangs and the only negative that I can remember is the the accessories (alternator, A/C, p/s, etc) run slower.

You may also have to get different belts, but other than that, it's a easy swap (at least on a 'stang).

Good luck,John

YouTube · Post by **EZcheese15** » Wed Nov 13, 2002 2:59 pm

I think the stock drive belt will work because you have only one serpentine belt and it has a spring loaded tensioner. Also, since you are only changing the crank pulley, it's not *that* big of difference I wouldn't think to require a different size belt.

But then again, who knows, I don't have one so I can't say

Post by **QuinGarcia** » Wed Nov 13, 2002 2:59 pm

The person to ask is the manufacturer, call their tech support before you buy. I would think that they would engineer it so that it would work fine on street cars. I'm assuming that they realize that your car is by no means a race car and will be driven on the street and must maintain street manners. I've heard of other people doing this and no one's had a problem. But, like he other fella, I have never heard of it on your specific car.However, I can imagine that your alternator's output at idle will be slightly reduced. If your alt. is only borderline now for your huge stereo system, maybe it could cause a problem

YouTube · Post by **EZcheese15** » Wed Nov 13, 2002 2:59 pm

QuinGarcia wrote:The person to ask is the manufacturer, call their tech support before you buy. I would think that they would engineer it so that it would work fine on street cars. I'm assuming that they realize that your car is by no means a race car and will be driven on the street and must maintain street manners. I've heard of other people doing this and no one's had a problem. But, like he other fella, I have never heard of it on your specific car.However, I can imagine that your alternator's output at idle will be slightly reduced. If your alt. is only borderline now for your huge stereo system, maybe it could cause a problem

The alternator on the Spec V's looks to be a pretty massive unit. I doubt it's borderline. The stereo is *only* 300 watts, not that crazy.

Also, my brother has a PS2, tv, amp, 10 disc changer, and extra battery in his spec V. He has no problems running it all.

Post by **Mayhem_J30** » Wed Nov 13, 2002 2:59 pm

i would suspect that a different belt size is needed...other wise it wouldn't be an "under drive" pulley. The tensioner might be able to handle it for a while until it stretches out..but that's a gamble you'll have to make. I have one installed on a completely different motor, but I got VERY good response out of it. If I can install it on mine you can do anything. Unorthodox racing should give you a list of recommended belt sizes for your vehicle on their website, along with some installation instructions.I wouldn't worry about under powering the alt or anything, just the shortened life expectancy of your motor due to the additional wear of no harmonic balancer on the UDP. Is the quoted 7hp worth that to you? It was for me but my gains were in the 15+hp range..so you be the judge.

YouTube · Post by **EZcheese15** » Wed Nov 13, 2002 2:59 pm

Mayhem_J30 wrote:i would suspect that a different belt size is needed...other wise it wouldn't be an "under drive" pulley. The tensioner might be able to handle it for a while until it stretches out..but that's a gamble you'll have to make. I have one installed on a completely different motor, but I got VERY good response out of it. If I can install it on mine you can do anything. Unorthodox racing should give you a list of recommended belt sizes for your vehicle on their website, along with some installation instructions.I wouldn't worry about under powering the alt or anything, just the shortened life expectancy of your motor due to the additional wear of no harmonic balancer on the UDP. Is the quoted 7hp worth that to you? It was for me but my gains were in the 15+hp range..so you be the judge.

I don't think we have a harmonic balancer built into the crank pulley on the QR25DE, do we? I really don't know for sure, but you do know some engines don't have harmonic balancers built in to the pulley. Also, Unorthodox usually is pretty good about making a pulley to balance out harmonics if so needed.

Like I said, take what I say with a grain of salt, it's really just speculation. But I wouldn't think it would be any harm.

Post by **djtodd** » Wed Nov 13, 2002 2:59 pm

If you need belts most of the time they have them listed here..

http://www.unorthodoxracing.com/belts.html

UR Underdrive Pulley

UR Underdrive Pulley

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