Contour Enthusiasts Group Archives Forums Modifications Duratec Performance what's the scoop on underdrive pully's???

hey all,

I have seen posts for the pro's and con's on underdive pully's, so what's the deal? Are they harmful? does the difference in weight make that big of a difference? thanks
Moose

Without dampening, the crank harmonics will damage the bearings and the crank itself. That's the theory anyway.

Several, like myself, have had UDP's on for over two years without ill effects. Doesn't mean it won't happen, but it just hasn't.

Personally, I plan on putting the DMD (dual mode dampener) on this fall, as I'm sick of the vibrations at higher RPM's and vaguely fear a blown bottom end.

-Lance

Originally posted by lkinley:

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vaguely fear a blown bottom end.

-Lance

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Did you get that on tape?

i just blew mine because of the crank was badly scored! however i had it warrentied, brand new block at 22500!

So how about the crank underdrive pulley AND the DMD? I'm thinking about these things while my car is down. Seems to me that the DMD would make up for lack of dampening from the underdrive pulley. Does that make sense? Anyone know for sure?

Originally posted by shotwell:

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So how about the crank underdrive pulley AND the DMD? I'm thinking about these things while my car is down. Seems to me that the DMD would make up for lack of dampening from the underdrive pulley. Does that make sense? Anyone know for sure?

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They do the same thing/Mount in the same place.

The DMD is a dual dampened crank pulley.

Trying to piggy-back and run both would be fruitless. You'd end up with a heavy UDP and still loose out on the dual dampening since the pulley orientation, location, and geometry would be all wrong for proper frequency dampening.

Skip the UDP crank pulley & use the DMD.

Not to mention that the larger DMD doesn't clear the frame rail when mounted to a UDP...

As for this...

Originally posted by lkinley:

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vaguely fear a blown bottom end.

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, I run a UDP and pray for a blown bottom end so that I can more easily justify stage two on my personal 3 liter project to my boss, uh, girlfriend.

How many of us are in the same boat, waiting for it to die to justify the cost of a new engine

With David Z. 30 minutes away I could have a nice new 3.0 put in for a couple-few grand. Although, with 68,000 miles the engine still runs fine, except for developing a few small oil leaks.....

Seriously, I'd be upset if it did blow right now, luckily there are no signs of impending doom "yet".

Originally posted by ScottK97SEMTX:

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Seriously, I'd be upset if it did blow right now, luckily there are no signs of impending doom "yet".

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You and Brad be sure to chip those redlines to 8K RPM...speed the crank whip process along a bit...

I'm sure it's been discussed before - but is there data that says the RPM operating range of the DMD is greater than the stock unit?

It is a tuned elastomer pulley which IIRC has a pretty narrow damping range (from tech tid bits from Terry and Judge), designed for cars that redline at about 7000 rpm. I would guess it is tuned for that range. Obvioulsy it has better "dual damping" for smooth operation, but is there proof that it'll be sufficient/better at 8000 rpm?

I would think you'd need a fluid damper or a high rpm tuned pulley for that??? If you look in the 2001 (or 2002) FMS catalog you'll see "race" dampers with cautins that they are not to be used over 8200 rpm, and thats a race damper.

Admittedly, I stopped reading alot of the DMD threads for a while, so I apologize if I'm rehashing old questions.