Pulley Size/Fitment: Z34 vs. R35
 

Alas...all this talk of torsional vibration has shaken me timid (pun indeed intended). I'll be going boosted very soon, and am looking for a replacement to the OEM crankshaft pulley. I've had the OEM size Stillen lightweight pulley installed for about 3000km with no discernible negative repercussions--that being said, I don't want to take any chances with the volatile mistress that is Forced Induction.

My internet detective skills have failed to yield any technical data on the stock R35 crankshaft pulley. Vital information such as diameter, serpentine ridge height (where the ridges start in relation to where the base of the pulley will sit), or even compatible belt width.

Using my eyeball deduction method, the R35 pulley and ours look very much similar in size--save the more robust extension downwards from the ridge, where our pulley just stops. From what I can tell, the "key" to the crankshaft it self is also the same.

What I would REALLY like, though I accept the unlikely hood of this request being answered, is a side by side picture comparison between the Z34 and R35 pulley. If they do indeed match, I will most likely purchase the Boost Logic GTR Crank Pulley, which is using an OEM size, and ATI's dampening technology.

Thank you all for your help, and have a greatastic day--supercalifragilisticexpialidocious, even.

I'm sure we have someone here who would be able to answer this.. But.. Have you tried contacting a gtr certified dealer on this? They should definitely be able to get that info for you since they always have a Z & gtr on hand.

I tried contacting my dealer, but they didn't have any GT-R pulleys sitting around...

Anybody here know anyone that manufactures the lightweight pulleys for our car and the GTR? I believe AMS makes one for both, but I'm inclined to think they will not reply my messages if I'm not buying their product lol.

In other words, BUMP =).

So just so we understand, you want to put a GT-R pulley, on a Z crankshaft?

:icon08:

Two different engines having different harmonics. Not recommended.

Just go with the OEM pulley for the Z34.

If you want something custom made that includes a damper, google Fluidampr.

But that shouldn't matter if I'm buying a harmonic damper--besides, considering similar bore, stroke, and overall similar construction of the two engines, I'm willing to bet a damper made for the GTR will still out dampen a stock 370Z pulley.

Fluidampr and ATI don't make pulleys for the 370Z yet. I've contacted both companies, and apparently "something is in the works." But considering that our engine uses the SAME pulley as on the HR 350Z engines, which have been out forever now...I'm not holding my breath.

Thats like saying this orange tastes better then that orange because it came from a bigger Tree... :ugh2:


6 to one, half a dozen to another br0. You're gonna waste a lot of $$ for no real gain... :ugh2:

Well, a DAMPENED GT-R pulley on a TURBO CHARGED 370Z. I was being pretty straightforward, no lines to read between.

I'm not trying to get a dampened pulley for gains...did you even ready my post? This is a preventative mod, for torsional vibration, which will be amplified by going boosted.

Isn't the Z Internally dampened... :ugh2:

NO. It is internally BALANCED. Torsional vibration will happen at the ends of a rotating shaft. That's where a damper comes in.

Ah, thought those were being used interchangeably, my bad. :tiphat:

Our stock pulleys actually do have SOME dampening characteristics. If you've ever seen a stock pulley, it has a rubber ring running the circumference of the bottom of the pulley. This ring will essentially absorb energies at a specific wavelength, lessening the effects of torsional vibration--however, as discussed many times before, some feel this little rubber ring is not sufficient for true dampening. IF IT WERE, companies like Fluidampr and ATI wouldn't exist...

Firing order, stroke, bore, crank length, combustion and most used operating Rpm ( many more im sure) determine how the engineers create these dampners. IF NOT those companies like ati and fluidampr could just make one end all be all dampner.

Hmm... I thought they'd custom make dampers if special ordered.

I think the stock part is probably desirable then -- the torsional vibrations associated with the GT-R motor may be different, so the dampening may be greater or lesser than needed for your application. In any case, lots of boosted Z34's are running the OEM damper without incident, so it should be fine.

Yeah...I mean...yes and no, right? Torsional vibration isn't magic. It's not like there are different TYPES of torsional vibration. The focus of the silicon/rubber is to absorb vibrational energies. The vibration is created by the turning of a weighted shaft between the two pivots. Assuming that the GT-R and 370Z have a similar weighted/length crankshaft, the vibrations would be similar at similar RPMs.

Torsional vibration isn't magic.

I forgot to mention magic...

I was being sarcastic, but you see where I'm coming from. Combustion would have NOTHING to do with torsional vibration. Why mention it?

PLUS, we've already established that the bore and stroke are VERY similar. I'm pretty sure the crankshaft itself is also almost identical in length. Weight would be the only factor--and EVEN THEN. Torsional vibration isn't magic lol.

seriously if there was no combustion we wouldn't need a dampner the rotating assembly would only need balanced. If you think it will be better then do it... no one is gonna pull any data to prove you otherwise. Actually you should call fluidampr or somebody and ask them questions about it.

There are already not a lot of boosted 370Z's out there. Of those that are, a few have have had problems. Torsional vibration will rear its head in the failure of other components (the oil pump, apparently, a common one). If I can spend $600.00, and simply reduce the chances of my vehicle running out of lubrication when driving, that's $600.00 well spent.

I do thank you all for your opinions and advice. I'm just going a route no one's gone before. Could work. Could not. Trying to use my limited understanding of physics, and some logic to figure things out.

I don't point things out just to be an ***; keep that in mind before judging me for my next comment.

If you are going to attempt to prove/disprove something, 7419, please use logic, and relevant information. YES, if there were no combustion, we wouldn't have this conversation. YES, if the glove didn't fit, Mr. OJ would have had a difficult time getting his hands in the glove. WHAT THE **** DOES IT MATTER to the question at hand?

Very similar means they still have slight differences, and slight differences at 7,500rpm become much bigger differences.

I don't understand theses moot arguments. Are people running around with lightweight pulleys that have NO dampening? Yes. Are there people running their boosted 370Z's with the OEM pulley? Yes. I do not have a sophiscated understanding of the complete mechanics behind torsional vibration; do you? I will assume no. With that being said, my understanding of torsional vibration leads me to believe that dampening this kind of vibration will be fairly straightforward--you take something that will absorbe the energy, like a fluid or a "spring" type solid like rubber, and stick it on the thing you want to dampen. Do you have any logical reason to suggest otherwise? If not, stop posting. I'm not saying I have proof, but most of us understands how vibrations and dampening works, I hope.

There is NO WAY our OEM pulley will have better dampening characteristics than the ATI dampner, even if it's made for a GT-R. Have you seen the little rubber ring? Lol

Please, guys, if you're not here to help with the original question, and are going to attack my reasoning, at least come with facts and logic.

Ill try to help one last time. Every engine has a different frequency that the dampners is designed for. You need to figure out which one your trying. For instance if a race dampners was designed for 10000 rpm it probably wouldn't be good for your car. A daily driver one would obviously dampen at lower frequencies. Basically what if our engines need dampening at 3000 and redline and the dampners you chose didn't do that extreme vibrations could damage your engine especially the more power you have.

Which...is the same RPM range as the GT-R...

No one's attacking you, we are offering our view points. But since you seem to have your mind made up, go ahead and do it. Maybe it'll work, maybe it won't. No one's tried it so why don't you be a first?

RPMs and the internal balancing from rotational mass, all the internals and so on are two different things. An F1 engine can do 7,000 rpm, just like a Honda Accord or Ferrari 458. They can both hit the same RPMs, but are entirely different engines.

I apologize if I'm a bit aggressive with my counterpoints. I deal with "factless" arguments a lot, so I get annoyed with them easily.

NOW, with that being said, I admit that my presumptions are rather baseless as well. I am going into this dampening business with two basic premises:

1) That overall, the GT-R and 370Z share a similar engine configuration
-I base this on the apparent similar fitting of the crankshaft pulley, size of shortblock (similar bore, stroke, and intake manifold fitting/size), and of course, an eyeball estimation of width to height ratio of the two engines.
2) That these similarities will mean similar crankshaft vibrations at similar RPM's.
-I base this on...well, nothing. It just makes sense to me that if 1 were true, there is no reason 2 wouldn't be.

Lastly, unless the harmonics of the engine were COMPLETELY off, I still believe that an engineered dampened pulley, at any RPM range within it's designed specifications (which is the same for the 370Z and GT-R), will out dampen the OEM 370Z pulley--which is practically undampened--save the little rubber ring. The added weight of the ATI pulley will also serve to dampen the vibrations by adding additional inertia.

I really don't mind people challenging me, or my ideas. I just don't like it when they make a comment w/o any support. It's like your grade 12 mathematics teacher always said, "show your work." ;)

BTW, I've already touched upon this. In reality, the only thing that should affect the harmonic characteristics of the two crankshafts would be the mass of the crankshafts themselves, but considering the breadth of variables considered (which I admit, I lack knowledge on), I've included some other engine specifications/estimations. Besides, if we're considering other variables, wouldn't you assume that a boosted VQ37VHR engine would behave more similarly to a VR38DETT? (I'm not saying the VQ will behave more like a VR than a VQ, just that a boosted VQ will behave more like VR than an NA VQ.)

The engine is already internally balanced, so there should be no "balancing" act needed for the pulley.

I've probably been a bit of an ******* to 7419sundat, so for that, once again, I apologize. Thanks for everyone's input, though! Still no answer...tried contact AMS, and no response, as I predicted.

That ******* was "butt-hole". ;)

Wow
 

You guys gave me a head ache but nice thread. I was curious about the Z's dampening. I've ordered an NST Pulley kit and I see your logic with a boosted engine. I had no idea the stock pulley had a rubber ring around it. Now I'm second guessing my NST. Will go SC next year, so I will keep my stock pulley around.

Subscribed, will fallow the thread to see if a supplier is found.. Thanks fellas.