Gentlemen, care to comment on these comments?:


A crank is a long, rigid metal shape; if you tap with a hammer it "rings" (especially forged cranks; cast cranks have some internal dampening). So what? Well, a hammer hitting it is only ONE way to cause the crank to RESONATE and exhibit harmonic VIBRATIONS. Another way is to RUN the engine! The engine is a vibration factory (as we all know)...and if left undamped, crank harmonics can build up at certain (harmonic) rpms and these vibrations DON'T just disappear, they have to be DISSIPATED! The best way to dissipate them is via the SPECIFICALLY-DESIGNED-TO-DO-THIS "Harmonic Dampener" hanging off the front of the crank. It has an elastomeric (rubber) isolator between the hub and the HEAVY outer ring, and is as a unit, designed to damp harmonics at the critical frequencies seen by the crank.

The heavier the outer ring, the better it damps, and the higher its efficiency at damping. NASCAR LONGtrack engines use HEAVY dampeners, to allow the bearings to live the long race length; the shorter the race, the more often the bearings get changed (after EVERY RACE), the LIGHTER a dampener can be used because lighter is a little faster to accelerate the engine due to lower rotational inertia. You are trading bearing/crank life for speed. Where do YOU want to go on this? Are you lucky?

The OTHER way to damp harmonic energy (which MUST GO SOMEWHERE) is through the main bearings, into the main bearing saddles on the BLOCK. This can cause premature wear/fatigue/flaking of main bearings, and cracks in the main bearing saddles on the block. This is a poor tradeoff for "an underdrive pulley".

Does this ALWAYS happen? No. Some people may not push their cars very hard very often; some may not do longtrack racing; some may not keep their cars long enough to discover the bearing wear, or to crack anything; the underlying design may be robust enough to cover over this MISTAKE in parts selection. There is a pretty big industry in harmonic dampeners, different TECHNIQUES for dampening (Fluidampr, ATI, BHJ, "The Rattler", etc) but they ALL DAMPEN HARMONICS because it is important. There may be some FREQUENTLY REBUILT race engines (?CART) that are not using dampeners but IF you think their ENGINEERS have not taken crank harmonics into account in their multi-multimillion dollar engine design, THEN there are worthless bridges to be sold to you...and foolish pennywise-pound foolish _NON DAMPENING_ "PULLEYS" to be sold.

As a person who comes to the hobby from an enginebuilder's standpoint (not sales/driver/etc) this misinformation about "you don't need a dampener" or when that fails "our unorthodox pulley does the same thing" is sad. It gets down to this. Do ya feel lucky? Well, do ya...? [Clint would say "punk" but that isn't my direction, just a good line ] This is an insult to your engine's health. It MAY take it in stride; but it is an offense. I respect my hardworking engine too much to burden it with the sometimes insane levels of harmonics that can occur without harmonic dampener protection. Where else are you going to cut corners? What other basic enginebuilding good practices is one going to spit on, and which will be the straw that breaks the camel's back...eventually?

This is a hotbutton issue with me. I never thought having a harmonic dampener would be considered "conservative enginebuilding" by some...geez.

PS: If anyone is interested in a REAL HARMONIC DAMPENER with underdrive for our cars, I am looking into having some made, because NHRA rules require an SFI-approved harmonic balancer for cars going into the 11's. With all the IDRA etc drag groups out there using NHRA tracks, better to be legal BEFORE someone challenges it/you and disqualifies you...".



--- Jack Tertadian


"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.".



--- Matt Monett (Dynamic Racing)








Final Comments:


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.
http://www.dinanbmw.com/html/danger_...er_pulleys.htm



--- Jack Tertadian



So it seems like damage will most likely occur, however its probably minute enough that you could get away with it before you sell your car.
I would liken it to smoking. Start at 17, then look at your lungs when your 65.

 

That is a lot of great info. None of them specifically discuss V6 engines. I wonder how different some of the physics are behind the big pushrod V8s and even the I6 the Dinan article talks about. I assume theoretically all types of engines will experience these stresses, but it would be helpful if there were specified info.

 

anything that has revolving mass I suppose. the rx-7 info is really null as it doesnt have a crankshaft, it has an eccentric shaft which is really not susceptable to the vibrations in a piston engine.
But the same holds true for v-8/v12/i4 engine configurations. i would suppose that the longer the crankshaft, the more delicate it is and in need of dampening. a v6 is probably not as susceptable as a v-16 (Cadillac v-16).

The main challange to creating the v-16 was all in the crank shaft.

 

i dont know if you missed this...

the RT TT referred to would be a Dodge Stealth RT TT, it carries a twin turbo 3.0 liter V6. And that guy Matt Monett owns the fastest one on the planet. So if you were wondering about performance of the UDP on a V6, there ya go. I must mention however that Matt Monett owns Dynamic Racing and is constantly tuning and modifying his car. so i dont know if his experiences would match up to those of the everyday guy. just a FYI.

 

That first post is right inline with everything I have ever heard about any engine. I have heard of plenty of Honda motors and GM motors blowing up while using aftermarket pulleys with no dampner built in. Spinning bearings and other odd engine failures you would expect from vibrations. They can't be directly proven to be the cause most of the time like a nitrous explosion can be blamed for a bent rod, but the evidence is there if you dig around a bit. I personally will not ever remove a dampner without replacing it with something equal or better.

 

This worries me just a tad bit as I have just ordered the UR SS kit hehehe

 

I was going to order but decided not to, after really researching the concept, the physics behind rotating masses, crank dynamics, counterbalancers, harmonics, dampeners.. it goes way beyond just cutting 4lbs off the crank pulley, it. I heard stories, theories and after all of it, I hav deducted its really not worth the negligeable hp you may get. Better bet is to go with the nismo flywheel on the other end of the engine.. this will be a better mod by far.

 

Wll FWIW, I took mine off and agree with the engineering apects of the original message as well as the result Vs. damage aspect of the never ending argument.

ASP pulley's are dampened just like stock just smaller and lighter and they are not called UDP's on LS1's they are called Harmonic Dampners.

So the UDP to me is car specific. My car runs fine with the stock ones, I didn't gain much so took them off.

Everyone should form their own onclusions though because thousands of people use them succefully as a good mod.

I wouldn't spray with them that's for sure though.

 

I have numerous friends that have been running them for years. I've been running them for years. I've NEVER heard of crank failure due to UD Pulley.

 

On the ASP's there are many stories of stalls in reverse, them coming loose etc.

It's hard to believe that not one person has ever had a problem with a balancer or pulley on an import when better designed ones have numerous documented problems.

Having said that people still run em and they can barely keep them in stock!

Even I had ASP on my LS1's!

 

The problem with the pullies on the LS1's is that the bolt holding them on cannot be re-used. Even if you buy a new bolt you have to tighten the thing to something like 125 ft lb's of torque or something pretty insane. With most hand tools you can't get it that tight. One time on a buddies formula I got all the cheater pipes I could find, put the car into 6th gear, put the ebrake on, and was still rotating the tires around before I could get it close to tight enough

The ASP pullies are pretty good because they have some kind of dampner built in. I would install a Fluid Damper, or something like that if they ever come out with one... and it proves to actually give some power. Most of the time you are lucky to get 2 horsepower -- which is within the margin of error from pull to pull on a dyno.

Personally, I'll just keep saving for cams and turbos

 

Exactly, very accurate info. This is why they come loose.

But like I said they can't keep then in stock!