D'oh

I completely agree that it is extremely unlikey for UR to have done that type of testing. I'm guessing that they worked hard to minimize the rotational inertia of the pulley (since that it what saps the engine power) while maintaining its strength to prevent it from cracking or deflecting too much.

The only thing I'm not sure of, is whether the lack of damping will have any effect on the Z's engine during normal running. At least if the Z's engine breaks we won't go falling out of the sky! I guess a few people will doing the testing for the rest of us.

Good Luck Suckers!!

(just kidding - hopefully everything will be fine)

-D'oh!

elektrik_juggernaut

I'm sure it will be fine, somebody correct me if i'm wrong, but i understand that honda engines didn't have dampers on them until the prelude.......and love 'em or hate 'em, hondas are pretty damned reliable

I've had the UR crank pulley on my MR2 for a long, long time.....and at 240K miles, the thing still runs great

dnguyen

I can see how the crank is generating torsional vibrations because of the torque generated for a certain duration by each cylinder and applied to different points along the crank's axis, but I am wondering why the crank pulley, which is "attached" to the rubber belt which is in turn "attached" to the other accessories, do not dissipate those vibrations through the whole belt "system". Maybe the surface of UR pulley that makes contact with the belt is too smooth, so the pulley just slips back and forth along the belt when vibration at that high of a frequency? The only thing that throws a wrench into this theory is that v-belts are design to expand into the groove of the pulley when bent thus increasing the frictional force...

N74DV

belts do not provide proper damping effect. They do not stretch with enough elasticity. They are very strong in tension.

Diesel350

iTrader: (6)

BUMP

Z Monster

Lightened flywheels would have a different harmonic frequency as well secondary to lessened weight. So, that makes them just as dangerous according to your theory since it mounts on the other side of the crankshaft and would not be weight balanced for the stock crank pulley. Does NISMO make a lightened flywheel? Methinks the sky is not falling on those of us running a lightened crank pulley.

http://www.courtesyparts.com/Merchan...=12310-RSZ30US

hfm

iTrader: (1)

You just had to do that. LOL!

I think I'm going to take the risk and add them despite the potential risk. They seem to produce serious NA hp. But, here is something to read:

http://dinancars.com/html/danger_of_power_pulleys.htm

hfm

iTrader: (1)

Does anyone have any information from older Nissans with the VQ engine, such as in the Maximas, to see if they've had any problems with lightweight pullies.

all_bark

iTrader: (5)

does anyone know of ANYONE beside max that has UR pullies on a Z and has snapped the crank?

anyone?

anyone at all?

maybe a brother of an old girlfriend?

anyone.....?

I did not think so....

all_bark

iTrader: (5)

and one more thing....

what would prevent someone who had an engine problem to, how should I say,

REMOVE THE UR PULLEY, PUT THE STOCK ONE BACK ON AND THEN TAKE IT IN FOR SERVICE?

How would nissan ever know?

Maybe you would get a brand new engine!

MY350Z.COM

iTrader: (2)

that's why i got the black pulleys.........looks stock

AFAIK none of the maxima guys have had any problems with the UR pulleys. And they've had it on for much longer than we have.

Victor

all_bark

iTrader: (5)

what is AFAIK?

MY350Z.COM

iTrader: (2)

as far as i know

PoWeRtRiP

oh man why did you have to bring this thread back. The "harmonic balancer" debate was pretty vicious a few months back. Had my UR pulleys on since june not a single probnlem. My favorite mod

N74DV

I gave up on this long ago..... I have my beliefs and for now am sticking to them. I know enough about harmonics to know that I feel much better leaving the stock pulley in place.... it ain't worth the risk for a measly 5-8 hp.

BriGuyMax

iTrader: (4)

Then stick to your "beliefs", but don't try to sway other people away from this mod simply because you did some math and read about a auto motor that somebody put a prop on...

You can do the math and speculate ALL DAY LONG...but in the end all you end up with is a headache.

I ran a UR crank pully on my VQ30DE motor in my 97 Maxima for 80,000 miles with NO ill effects at all. I freed up a good bit of low end to mid range torque and added 2mph to my 1/4 mile traps.

That to me is MUCH more proof that Lightened Underdriven crank pullies are no more damaging to my motor than an intake is.

frenzee

iTrader: (1)

I guess I missed thie "heated discussion" a few months back and am too lazy to dig that far back, but I just read N74DV's first post and although I agree with everything he says, I would like to add my $.02:

- The theory of stress on the crankshaft due to harmonic resonance is absolutely correct but in an automotive application an engine’s RPM and torque load, which determine the harmonic, vary constantly and considerably. The effect would be much more pronounced in the example of an airplane which he cites, where you don’t have a throttle pedal, but a lever which in level flight you set at a constant rate and leave it there for minutes or hours and if that setting happens to be where the crank starts to resonate then yes, you're in trouble. But in a car, you are much more likely to cross the range of resonance frequency only briefly as you rev up or down the RPM range, and that RPM where things start to resonate isn't a fixed range either, as the torque load on the engine will push that number up or down as well. Assuming you do reach the harmonic frequency, just a couple hundred RPMs more or less (or a few lb./ft. of torque more or less load) and the harmonic will dissipate. IMHO, manufacturers put the harmonic balancer is there primarily to make the engine rev more smoothly and also to reduce the fatigue on the main bearings and journals. Will you sacrifice some engine life for a little (extremely little in my opinion BTW) extra power? Absolutely, no question, but snapping the crankshaft in half due to UR pulleys alone would be a very unlikely event, IMO.

N74DV

lay off dickwad..... that's what these forums are for.... for all of us to offer our own opinions.

BriGuyMax

iTrader: (4)

Yes they are...BUT you have no PROOF that pullies hurt our motor.

Read frenzee's post...the application you cited was much more stressful to the motor than our application.

Wow...I just realized how old this thread is...

November four seven delta victor.....hot car...like the rims

Sorry if I came off a little harsh the first time...I just hate it when people knock mods and then tell individuals whom use those mods that they are going to break their motor.

I tend to come off harsh to pilots anyway sometime...comes with the job

FairladyZ

n74dv,

Your right bro. I had an LS1 b4 my Z, and the pulley on the LS1 was a harmonic balancer. Originally no one paid much attention to it until LS1 edit and dynos came around. They found out that the original aftermarket pulley would cause our motors to detinate (sp), etc. So on the dyno there would be a spikes on the graph which came up as losses or the dynos would be real jagged meaning bad running motors.

So everyone chunked the old pulley. Eventully a company called ASP made the pulley for the LS1 right. They could never keep the pulley in stock. Not sure about now though. I got one for my WS6.

So the question is, is the crank pulley for the Z a hamonic balancer of some sort. If so I will not purchase the pulley.