There was/ is (always will be?) an ongoing debate to whether the main crank pulley (sometimes referred to as a dampner) is specifically balanced against the cranks in our motors-

OR to put it another way: whether or not a lighter, smaller UR Pulley will damage our motors over time due to an imbalance.

I have an 03.5 sedan and had my UR installed early in 2004. My car has lost a little bit of its jump- but I associate that to needing my MAF cleaned.

I've had zero trouble w/ the pulley thus far until recently- Now I'm hearing a slight squeaking, kind of griding/wearing sound coming from the front of my block. I'm not sure what it could be- and it could be nothing. (it's only slight)


Either way, everyone with Pulleys; CHECK IN. Any issues?

 

Check out this post from Z1:

http://my350z.com/forum/showpost.php...0&postcount=10

 

Thanks Trey for the article. I don't doubt the info at all (hence I installed the UR pulley..)

- I'm not (believe me here..) trying to start THAT debate again.. just trying to acknowledge it and then hopefully get updates from others that have installed pulleys. Anyway- I do feel better regardless.

 

Do you guys prefer one brand over the other. How many brands are there?

 

I get the squeek too sometimes when I start the car. Especially if it's cold. The belts need to be tightened. I've been a little lazy in getting it done, it's just a little annoying.

 

After 2.5 years with the UR set, no problems. The stories of broken cranks and scored bearings were mainly on BMW inline 6. The length of that motor could create some serious twist and snapback resonance along the crank. If not damped, see ya. Remember the film of the Tacoma narrows bridge twisting and then coming apart? Now speed up the film 1000X, that's what it looks like in a motor.

 

I always thought the pulley debate was funny.....People bash a pulley but have no problems putting a light flywheel on the other end of the crank.......

 

honestly I never looked past UR.. and I will reiterate that I LOVE this mod- the RPM's spin up so quick-- big difference. (I only did the crank though as I didn't want to underdrive my alternator at all in case I was going to do some audio work.)

I had stillen put mine on.

 

Is the one you put on the stock size then?

 

I completely disagree with that guys post and it's totally wrong. He knows absolutely nothing concerning this subject. People need to understand that "balanced" reciprocating assemblies have NOTHING to do torsional vibration placed on a crank during combustion. Sure, if you could spin that the assembly without pistons firing, then yes, it's balanced. But when you throw in timed explosions pushing down on pistons and twisting a crank, things change dramatically. During combustion and at various rpms, the crank has to deal with all kinds of orders of vibration.

The stock pulley is indeed a crank damper and the pulley is balanced. The pulley is both balanced for weight distribution and various order vibrations sent through the crank. if you don't believe me, look at the back of your stock pulley and you'll see 3 to 5 dimples. That is shaved weight from the pulley so that it is balanced to the crank. The stock pulley is a two piece unit connected by a sandwiched elastomer ring. This ring is the damper. It's not there to "quiet accessories" as some tell you.

Why doesn't the other end of the crank need a damper? Because the 35-40lbs flywheel or torque converter act as a damper thanks to their weight and diameter.

As for damage caused by a lightweight undampened crank pulley on VQ35, I don't think it will happen. The VQ is a stout motor with a short forged crank, 4 bolt mains, and girdle.

As for gains from the UDP, I don't think so. Removing 5lbs of rotating weight from a 6" pulley connected directed to the crank won't make a lick of difference. For one, the diameter is extremely small. Accelerating a 6" pulley is far easier to acclerate than a 12" pulley. Finally, since the pulley is connected to crank, there is very little power needed to spin the pulley. The further away the rotating device is from the crank, the harder it is to accelerate.

Finally:

https://g35driver.com/forums/showthr...highlight=dyno

 

And you do? LOL

 

My cat's breath smells like cat food.

 

Also, if the UDP was such a great thing, then why don't race-spec VQ's run UDPs? If you've ever seen one, you'd see that they either run the stock pulley or they run 3lb+ heavier aftermarket crank fluid dampers. This goes for every other race-spec motor out there.

The whole notion that UDPs gain power stems from the Mustang crowd. UDPs on a 5.0 are good for 8-10whp, BUT the pulleys significantly underdrive the water pump and that's where nearly all the gains come from. The VQ water pump is driven by the timing chain therefore having a UDP does nothing to the water pump.

 

Don't forget about the charge on the alternator as well. You sometimes have to give a rev or 2 at a stop b/c things start to dim and the voltage drops.
But it was good for about 8whp on my GT.
The mustang crowd strikes again!

 

The UDP made a difference on my maxima Dave. It did indeed rev up a bit faster. Which the VE needed badly.

I can't see the oem pulley being a dampener. IMHO, the rubber ring is much too thin to do anything. Maybe to soften the accessory shock but that's it. Again IMHO.

The oem pulley is balanced but so are the aftermarket units. Only if the oem unit was balanced with the crank and flywheel (if installed) would it "might" make a diff. But I highly doubt Nissan really balances them out that much.

And Russ, don't talk **** unless you got something to add. I'm watching this thread for info (for and against). Take the pee-pee waving somewhere else.