Destroying the dogma: lightweight crankpulleys

[DrkZide]

What about a TT LS1? Drop that sucker on a Corvette drive train and you're gold. No more insufficient aftermarket woes

[mb7050]

lol not going to argue with you, I'm sure driving 150 MPH constantly had nothing to do with engine failure on a 10+ year old car.

no need to argue about anything . actually that car was 9 years old back then and 70k miles on the clock (2004) not that it matters anyway I´m still not saying UDP pulley caused it .

[hotGTO]

Why would a manufacturer waste the money and sacrifice the hp on a part like that if it made zero difference. There is no explanation except that it is needed to serve it's purpose. Why would they still be using them in new motors today if they are not needed?

[Chris@Rvengeperformance]

who said they make no difference?

To me personally, for the power output I'm shooting for, the risk of the stock pulley seperating outweighs any risk of an UDP causing an issue. I've seen plenty of engines wiped out by the stock pulley seperating and so far no concrete failures caused by a solid pulley.

If you want to replace the stock pulley every 5 years or so then go right ahead, meanwhile I'll be thousands of miles down the road still running my original solid like I have been forever.

Just don't pretend like your engine is going to magically going to fall apart using a part that has been proven to work for over a decade and scare all of these guys with UDPs to run to the nearest mechanic to get them replaced. Some of the biggest names in our market have used them extremely successfully for YEARS.

[mb7050]

this
I Dont´t want oem pulley for my engine
I Don't want an underdrive pulley
I Don't want a pulley w/o a harmonic damper
I Don't care if the pulley is heavier or lighter.
I want superior damping for my engine !

I am not going to hit autobahn with the undampened pulley that I currently have.

[Hammer]

well, thats to say if the 6g72 had a better option we could. as it is the OE damper only neutralizes a very small range anyway, and after a change of internals its range of operation is even smaller.

What do you know about the "modified" Evo engine?? was it rebalanced after the internals were changed?

I can add in aircraft harmonic dampners are considered too heavy and not used. What they do instead is placard a warning "Do not operate this engine in this range usually like 1,800-1,900 RPM for any length of time." That would be identified as the specific range where damage can be done to the engine. Now it is possible that some of the people that never have had a problem using underdrive light weight pullys have just by luck managed to stay outside of the danger zone for our engine. It would be nice to know what RPM range is considered dangerous to operate in. Of course like has already been said it will be different if you change out some of the rotating parts. But for the stock engine with stock parts we should be able to find out the dangerous RPM zone of operation. Because most engines use these and in auto world are considered needed then I would guess the dnagerous RPM zone is probably one that we use quite frequently. Maybe like cruising at 65 MPH in high gear on the highway. Just guessing out loud.

[J. Fast]

No one is denying the fact that all multicylinder cars experience low torque vibration and high torque vibration (one at low RPM and one at high RPM). Quite plainly you can almost hear the difference in the engine putt's when you approach harmonic problem areas. If you want to conduct a little test you can drive towards a 2% grade hill and approach it doing 50mph in the highest gear (5th or 6th depending on your model). Without changing gears floor it about 100ft into the climb. There will be a specific speed and rpm range where your car starts to resonate sound and vibrate. It will start to vibrate the rearview mirror like crazy and will even change the tone of the exhaust and maybe make a few things rattle. Well, if you hear that sound... that's what your dampener is designed for absorbing. If you drive your car like that without switching gears... you need a harmonic dampener (and a driving lesson). I personally drive my vehicle in the heart of my gears and don't go storming up steep grades doing 65mph in 6th gear or 65mph in 2nd gear. Again, roll thru the gears.

Jeremy

[DrkZide]

I have solid motor mounts so that vibration is pretty apparent. It was the same when I had the stock dampener vs the UDP. I also get that vibration in first when I start driving the car.

[i3igpete]

Without changing gears floor it about 100ft into the climb. There will be a specific speed and rpm range where your car starts to resonate sound and vibrate. It will start to vibrate the rearview mirror like crazy and will even change the tone of the exhaust and maybe make a few things rattle. Well, if you hear that sound... that's what your dampener is designed for absorbing

Incorrect, that low rpm vibration is NOT crankshaft torsionals. It's the natural frequency of your engine/transmission and the mounting system. This is tuned separately and the paper in the OP mentions it briefly on page 6. These are typically in the frequency region if you can feel a rumbling sensation - you can't feel vibration of the crank twisting because it is too high of a frequency.

I also deal with engine mount dynamics in my work. Here is a typical analysis of mounting system natural vibration.

[J. Fast]

I'm assuming those are graphs of 360 degree crank rototations (60 degree each maybe)?

i3igpete

...low rpm vibration is NOT crankshaft torsionals. It's the natural frequency of your engine/transmission and the mounting system.

Out of curiosity, how many natural frequencies are there in an engine?

Jeremy