"Crank up your boost for more power, and leave the stock crank pully for maximum engine life, aftermarket pullies have no dampner ring in them.
Not thats its that bad, bad for longevity on a daily driven car, completly differant scenario for a racing setup, becouse of the low milage a race setup would get.
You might be fine for years, hard to say, but crankshaft harmonics will in time, snap the crank.
And look at it this way, why would the engineers spend so much time developing that engine and put a harmonic balancer on it in the first place?
I always have a hard time recomending pullies, for street setups, but they do make HP. Good for power, does not make a product "good" When you snap the snout off your crankshaft, you'll get a better understanding."

and

"ok i heard bad for some cars... in particular the 3000gt twin turbo, but the power gain was good.

"The other benefit of aftermarket pulleys is to reduce rotating mass. Here the simple aluminum crank pulley has a big advantage over the heavy stock pulley, but there's a reason it's so much lighter: It's missing the harmonic dampener. The reduction in rotating mass may be worth a couple of horsepower. But removing the dampener seems like a bad idea to us.

The factory crank pulley has a built-in harmonic dampener, in the form of a split design, with a thick rubber pad sandwiched between two steel sheels. The dampener is designed to absorb torsional and vertical vibrations from the crank. MOST underdrive crank pulleys (with the exception of the Buschur Racing model) do not have a harmonic dampener at all.

Torsional vibration is a twisting vibration caused by the pulses of each combustion event. The force of the piston causes the crank to deflect ever so slightly in the direction of the force, and when that force goes away the crank ever-so-slightly springs back. At certain frequencies the crank can resonate, making the vibration much worse. This is where the harmonic dampener comes into play."

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so apperantly because the LightWeight Pullies don't have Harmonic Dampeners... they are bad for the engine and can result in "snap the snout off your crankshaft"

can anybody at to it or...?

worried....

-ilon.

 

here we go again....

I have this funny feeling any and all performance mod I've put on my car has decreased engine life.

 

Yep. This topic has LONG been debated over & over again. I think you're better off asking who actually "snap the snout off your crankshaft" from installing an aftermarket pulley. BTW...any aftermarket part you install will decrease your engine life.

 

This may not directly apply to Vq's but on the JDM Subaru Sti motors the pulley has a rubber damper, on the usdm motors it doesnt. The JDM motors rev to 8250 stock, and are have a very smooth and balanced feel, while the usdm rev to 6800 and feel like crap.

I am not a fan of pulley's, but i dont think they are going to do any definite harm either. I just feel the damper is there for a reason.

Dave-

 

I agree, somethings are better left alone and the harmonic balencer demper pully is one of them. Yes it`s a simple and easy mod to gain a few ponies but IMO it`s going to cost you down the road. There are other ways to make up the difference on horse power I for exsample would like to get a set of 17 x 8.0 lighter wheels that look great and I know it wont hurt my ingine. Just my 2 cents...

 

I think snapping off the snout is a little extreme. The biggest issue I think is increased bearing wear in the number 1 journal of the crankshaft.

 

Some of us who have sustained high rpm usage especially to 7200, dont like them. For as hard as I push the car it just is not worth it. I think for most it would not be troublesome.

 

The non usdm STi's still use the 2.0 liter engine, far smoother than the beefy 2.5 we get.

 

hehe i know. Import JDM sti's for a living. I have had 3 JDM swapped subies

believe me i know all there is to know about JDM cars..

 

I think the harmonic balance is only an issue with the underdrive pulleys. Search for the KJR pulley . It is the same size as the stock, just lighter. This makes it so that you can also use the stock belts.

 

Who is this quoted authority? If I look, I can probably find another qualified engineer that will say the lightened pulleys are safe. I have examined crank bearings that can come from VQ's with a lightened crank pulley....after 15,000 miles on the motor, they were nearly perfect. This theory has gone back and forth so many times. I say they are safe...but that is my opinion.

 

It almost looks like part of the write-up that somebody posted a link to from the Dinan BMW site (http://dinancars.com/whitepapersFile.asp?ID=5). Apparently he doesn't like them. IIRC, it also pointed out that the BMW has a real harmonic balancer as opposed to a rubber damped pulley like the Z has.

 

i think people who are modding their cars a lot will have bigger problems to worry about than what the pulley might cause. There's been a few people who have run them for over 60k miles and no issues yet.

 

why doesnt someone make a lightweight pulley with some rubber in it?

 

so everybody says they're the worst mod you can have for the enigne but noone has actually had a problem with them yet right?

Considering my car is FI, I don't think I can do anything worse to it! LOL

 

I push my car to 7200 nearly 3 times a day with UR crank pulley... haven't got any problem yet after 6K km since the engine was rebuilt... and my engine builder (ex-head engineer of Gybson motorsports in Australia who built GTR engines for racing in early '90s) did not say anything about the light weight crank pulley that I am using either.

cheers,

richie

 

there is no dampener on the stock pulley...period. There is an isolator, and Dave is right, it is there for a reason.....to reduce noise from the accessory belts...that is it - for aboslutely NO other reason

this thread needs to die....it's insane how many times we go over the same things on this site.

Anything you hang on the crank of this motor needs to balanced. Believe me when I tell you the UR pulley is balanced perfectly....much better than the stamped stock pulley is (check for yourself if you don't believe me)

45k on my car, pulley since the second night I had the car, car has redlined at 7100 since the car was 2 months old....never an issue on this, nor on ANY other car I have ever used an UR pulley on.

Some cars are not designed to bolt on a pulley - the Nissan V6, be it a VG or a VQ series is NOT one of them - I have customers with 200k + on their 300 ZX twin turbo's without an issue (VG series 3,0 liter V6 - the predecessor to the VQ).

 

64000 miles... no problems... and I also have a light weight flywheel...

stock pulley doesnt have a damper on it either, and is probably not as well ballanced as the CNC'ed UR pulley's...

 

Awesome info...

Someone needs to make thread to get sticky'd that tells common misconception about certain mods on our cars. This would probably be at the top of the list.

 

hmmm... sounds like you need to practice what you preach.