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The Right And The Wrong Ones To Use
Current information contributed by Team3S members.
Article by Cody Graham
Special thanks to Jack Tertadian, Roger Gerl, Matt Jannusch, & Matt Monett
This discussion comes up several times a year on our Team3S owners' list. Please search our archives for numerous past conversations on this topic. Start at: www.Team3S.com/Search.htm. Enter a search term like "Underdrive Pulley" (duh), "UDP", or (one spirited thread was), "Unorthodox Pulley Is Bad For Engine". It has been hashed and rehashed a million times over, but here's my summary, followed by a number of comments from Team3S members.
May be extremely dangerous to your engine. The underdrive pulleys that Unorthodox Racing sells are not harmonic balancers. Meaning, your engine may do things its not supposed to. Such as..., spin crank bearings.
Will spin all your accessories slower. If they were meant to be spun slower, don't you think they woulda done it from the factory that way!?!
Will give you on the order of 5 HP - yes..., I said 5.
Are illegal for use in drag racing applications.
Our engines are designed with harmonic balancers.
"I would not get one. Though they are a PULLEY, they are not any longer
HARMONIC DAMPENERS. The original purpose of that heavy disc on the
front of all car engines is as a harmonic dampener; Mitsu just added a
serpentine belt pulley on its outside aspect as a space-saving effort,
so it does 2 functions at once. The original and more important
function is still dampening crankshaft harmonics.
--- Jack Tertadian
"I once played with such pulley on the Camaro and some of us really saw a gain ... It was around 2-5hp. This is within any tolerances on the dyno and of a few degrees on the ambient. The drawback is now a much harder steering for daily driving, dimming lights during idling, and slowing down fans at idle as well.".
--- Roger Gerl
"The Buschur pulleys contain a torsional damper assembly (essentially a section of rubber connecting the two halves of the pulley). This allows the pulley to act as a damper against the harmonic vibrations in the crankshaft caused by the cylinders firing. It is very important to keep the harmonics damped in some fashion to prevent bearing damage. Of course, the Unorthodox folks will say that the car's accessories provide this damping, which is completely false, as a counterweight is required to perform the damping action. The counterweight is supplied by the rubber section allowing the pulley to twist and let the inertia of the outer pulley ring counteract the torsional flex of the crank.".
--- Matt Jannusch
"My car (93 RT TT) has had a Unorthodox Underdrive Pulley on it for about 2 1/2 yrs & 30,000 miles now, and my car spends A LOT of time at 6000+rpm, in facked, my car held 6700rpm in 5th gear for over 40 miles strait! My partner (92 RT TT) also has had his pulley on for about the same time and miles with NO problems! To add to it we have sold 100's of these with not even 1 complaint! Every1 that I have talked to after they installed the pulley has told me about the same thing 'it does feel to have a little more kick' or something along those lines. Every bad thing I have ever herd about these pulleys is from some1 that has never tried it, nor have I ever even herd of a bottom end failure that can be linked to 1 of these pulleys. But like anything make up your own mined, but I can tell you the pulleys work and I know of know problems related to them.".
Anyway... just search the archives - you will find some positive quotes as well on the underdrive pulley, but I would stay away from them, especially for 5 HP, maybe 10... It's just not worth it. NOS is easier on an engine than an UDP without an harmonic balancer... Caveat Emptor.
--- Cody Graham
For the SCIENCE of UNdampened UD pulleys, this is about the best article
I've seen, by Steve Dinan. Read it - understand it - THEN decide for
yourself, and if you THEN get a UD pulley you can honestly ADMIT it IS
damaging but you have accepted that level of engine unhappiness.
--- Jack Tertadian
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