neffster

iTrader: (2)

The following post is from an Infiniti Technician in CA. He claims to have worked on Infiniti's for 13 years... He tells a story of 2 VQ35 engine failures as a DIRECT RESULT OF THE UR Underdrive Crank Pulley.

I am hoping to start an intelligent conversation, and potentially weed out a few technical guru's and get their inputs.

His message from G35driver.com (technical and mod forum) states...

InfinitiTech (Registered)
05/03/04 08:07 PM

Okay guys,
I could lose my job over this. Here is the information for whatever it is worth.

Case 1:
2003 G35 with 32,566 miles on it, exhaust system, intake manifold and tube, crank pulley. Customer complains of engine knock noise. Isolated it to main bearings making noise. We had the regional engineer come out with his digital stethoscope and that is how we isolated it to the bearings. He used a tool we have called electronic ears, which can actually get a hertz signal from the anything that vibrates. We took the aftermarket pulley off the vehicle and installed it on a similiar 2003, and measured the readings before and after. There was significant difference between the stock pulley and the aftermarket. The motor is balanced internally but balanced with the stock pulley on the motor, maybe the weight difference caused it, who knows. So the engineer boiled it down to the pulley as being the cause of the excessive vibration causing premature wear on the front main bearing.

Case 2:
2003 G35 with 38,334 miles on it. Similiar noise but this vehicle had the stock pulley on it. I myself inspected and worked on this vehicle. But as you all know to the trained eye, I could tell someone had removed the stock pulley. As one of the bolts was almost completely stripped. So logic would tell me, after seeing the usual modifications the engine, intake,intake tube, hi flow cats, exhaust, brakes, etc...One would assume he had the aftermarket pulley on and removed it because he still had warranty on it. I turned a blind eye to the matter and warrantied his motor, and had a little conversation on the side with the customer. He came back later with a case of wine for me and said he deeply appreciated the effort I had done.
There you have it, you guys can decide for yourself after reading that. I am not a referee here, just relaying information to fellow G35 drivers. Maybe it is a fluke this happened to these cars, maybe not. I came to my own conclusion about it. Take it or leave it. Oh yeah the engineer who knows more about the design of these cars agreed as well. By the way, they other guys insurance company bought him a long block, was not covered under warranty.
I am not discouraged by Six foot guy, or at what he was saying. I am on all your sides, and that is why I am here.

Infiniti Gearhead

Thanks for reading,
Neffster

ypwpat

this seems mostly happen on G35 owner. Any case with 350Z owner yet? I just installed mine today too

zillinois

iTrader: (6)

Thanks for sharing the info.

Jetpilot718

Could make sense, but I just dont see how changing the rotational mass of something (not the diameter) could effect balancing. But then again, its stuff like this that makes me wanna stay stock...

AndyB

Although this information is interesting, I am not sure if it proves anything yet. Correlation and causation are two different things.

I would not be suprised if a lighter pulley made a certain harmonic louder in the stethoscope. The heavier stock pulley probably works to dampen vibration to some degree. That would explain the sounds they heard. However, that does not mean that the lighter pulley caused the failure.

I am not saying the pulley could not have caused it either. I am just saying that it is too early to draw conclusions in my opinion.

But this IS interesting information. (and an interesting diagnostic technique. Sounds like a good technician)

VandyZ

iTrader: (2)

I know of one 350Z that has suffered due to pulley. When I say suffered I mean SUFFERED.

ypwpat

like what?

jckolnturn

iTrader: (1)

How can you narrow it down to just the pulley when there are numerous other owners of Z's and G's that are running with the pulley with no problems.

FairladyZ

so you think.....How many miles you have on your car? No info from the Z guys because Z techs dont come on this website like they do on g35. Thanks for the info, I am glad I didnt get a pulley.

Dissolved

Yep. That's why I dont have one. Thanks for the info

westpak

iTrader: (19)

Would that mean that a light flywheel would have a similar effect?

jesseenglish

I think it's less because of the weight, and more because the UR pulleys don't have the rubber harmonic damper on them. It's pretty hard to narrow it down to a pulley although the circumstances are suspicious. Engine failing at ~30,000 miles from main bearing failure would definitely point towards excessive vibration in the crank.

mcduck

If this turns out to be true, I doubt a lightweight flywheel would do the same thing. According to the post above, the engine is balanced with the crank pulley on it. I'm willing to bet the flywheel is bolted up after balancing. Just a guess, tho... anyone have a way to verify this.

For the record, I had the UR Crank pulley on my car for 5000 miles with no problems that I am aware of. Would have kept it, but the Vortech SC required me to go back to the stock crank pulley.

jckolnturn

iTrader: (1)

pulley thread
https://my350z.com/forum/showthread....8&goto=newpost

jckolnturn

iTrader: (1)

It has nothing do with balancing, the engine is balanced internally. The claim against the pulley's invloves damping vibrations, read the above thread for the full heated argument and more than you would care to know about vibrations and damping.

jesseenglish

The engine is internally balanced. I would hope that any aftermarket flywheel is balanced itself. I come from the old school of aircooled VW's and it's unthinkable to me to put an aftermarket flywheel on it without first checking it's balance because they don't come that way from the factory. I always assumed that the new flywheels nowadays are balanced as part of the manufacturing process. That should be the question that's asked.

jpc350z

Agreed that changing rotating mass would not in itself cause an unbalance as long as the mass is dynamically balanced about its spin axis..Any unbalance results in an offset load on whatever it is attached to..Bearings see a uneven load and wear out quicker..

PoWeRtRiP

though this seems very convincing im the check your sources kind of guy and this all seems to shady to be concrete evidence. id like to see some real facts not just a guy that heard about it from a tech who was letting him in on it. if this is true then we might need to rethink this mod. but can you guys show me one z owner who had this problem? and we all know that infiniti is much stiffer on mods than nissan is.

FairladyZ

I think the "tech" posted this on a forum. A link to the post would be very nice.

all_bark

iTrader: (5)

makes me reconsider my pulley install.

should I remove it?!?!?!?!?!?!