phunk

iTrader: (21)

i think that quote is some sales BS. Building that harmonic dampener is easily more expensive then an aluminum pulley. They could simply use heavy gauge stamped steel for it if they wanted it cheap and light, and they dont.

hfm

iTrader: (1)

Well I've spoken with my tech contact who is "in the know." Please don't ask me to post names, I simply wont. Suffice it to say that I know I can trust his opinion and would stake my car on that belief.

He says that regarding the UR pullies, there is no reliable evidence for the Z33. He's followed Z32 for years. For Z32, it's okay. However, recognize that it's a totally different engine, cast iron block, not aluminum. Unorthodox racing produces quality products but he says, lets face it, they do not do any durability testing anymore so than anyone else. There is a small risk. If horsepower that important, go for it. If something goes wrong, do a reinstall of the stock pully and belt before taking it back to the dealership for any warranty work.

As for the last comment, I do not recommend any misleading or fraudulent action. And, it's personally something I would not do.

So, I'm settled on this issue. Who has the cheapest price? I understand the crank pully can be had for about $220 with an additional 15% discount.

SoFl_G

iTrader: (1)

Not to add fuel to this Fire, not having looked closely at my G's crank pully and hub. I have one question to those that have. Does the pully bolt directly to the crank hub itself, or to the outer ring that is supported by rubber. If it is bolted to the central hub only and the outer rubber suspended ring is not connected then it is undoubtly a harmonic dampener. If the main pully is however bolted to the outer rubber suspended ring then we are talkng NVH dampining. The outer ring on a harmonic dampener can get quite active with vibration and the engineers would not wish to subject the accesories and belts to this kind of possible intense vibration. The design of the stock hub should tell us a lot about what was intended.
Also just as an aside, the longer the crank, the more necessary the harmonic dampener is. The v-6 configuration is the shortest crankshaft design currently used in production vehicles. Inline 4's and V-8's have the next longest. That is why you will find harmonic dampeners on v-8's and why the LS-1 folks found a dampener necessary. I don't even want to go into inline 6's. I suspect you WILL find a dampener on every I-6 ever built.

Z1 Performance

iTrader: (564)

SoFI_G - thansk for your intelligent post! I will post a picture of my stock hub tomorrow (just did the UR pulley this afternoon since it was quiet at the shop - very noticeable difference in pull from about 4k onwards).

we've used the on flat 4's time and time again and have not once had a motor let go......

N74DV

here's some good reading...

http://www.epi-eng.com/ET-TorsAbsrbrs.htm

they even mention the older Z engine.

Z1 Performance

iTrader: (564)

Thing is though, you do not need sch a dampener at all on an I-6 motor, provided the bottom end is balanced with your intended pulley on it to begin with.

As I said, some cars can use these very effectively (the VQ motor, Subaru, and others are perfect examples), some motor cannot (BMW for example, which have notoriously wimpy bottom ends due largely to the cheesy bearings they use)

jcv

Here's a good reference on this from a knowledgeable automotive source that explains it pretty well if you're interested.
look under white papers for pulleys
http://dinancars.com/default.htm

And I take some exception to the BMW's cheesy bottom ends- seem to hold up pretty good on the track and put out plenty of hp from those wimpy straight sixes. Been doing it for years.

zillinois

iTrader: (6)

You had a prop from an airplane attached to your z motor and it blew a rod from lack of harmonic balancer. You are a funny man!

Z1 Performance

iTrader: (564)

jcv - have you seen the bottom end of the BMW straight 6? Ever build one? Ever race one? I have - our shop owns and races 2 as a matter of fact (both race cars, and E30 and E36) - they are among the most underengineered bottom ends out there...mostnotably due to sheer lack of adequate bearings. Hvaing taken the motors apart, I can tell you that a solid buildup of a BMW bottom end is worth its weight in gold. By comparison, the bottom end of my 280ZX (even in original NA guise) is incredibly strong from the factory . very stout main bearings, and just generally good components used throughout. The BMW on the other hand was clearly a cost cutting measure both in the E30 and E36. Granted they are still great cars to race, but some care needs to be taken when running one competitively.

I agree 150% with Mr. Dinnans case for NOT using a pulley on an otherwise standard BMW motor - the motor is simply not engineered well enough to compensate for the pulley, due to the reasons I described above. However, if you are building a BMW block (or any block) from the ground up, you most certainly can use a pulley with such a dampener, as you will simply be balancing everything at once during the buildup.

Again, the VQ motor has been out for a long time now, with many examples running well over 200k...its a stout design, and will easily be able to handle a properly designed lightwight pulley.


Adam

vfr350

Can anyone post a picture of the backside of the stock crank pulley or confirm that the stock crank pulley is a multiple part unit that vulcanized ring on it??

zillinois

iTrader: (6)

Here is a pic. The second ring in from the center is rubberized. Not in the hub area but the outer ring area.

Z Monster

I'll do the Chicken Littles a favor and post a pic of the stock crank pulley hub so this thread can die with dignity. Viola, no rubber on the stock crank hub.

vfr350

Thanks zillinios for the pic. I least now I know that it actually is a dampener or is intended to reduce some harmonic type vibration.

Z Monster

Side by side with the UR pulley. Notice the outer diameter of the UR pulley vs. the rubberized O ring pressed into the stock pulley (as the 'O ring' does not go all the way through the stock pulley{front to back}). Perhaps, the mass difference from the O Ring out needs resonance dampering. The lower mass/lower rotational inertia UR pulley may be exempt.

reen

N74DV makes many good points and is consistently spot on, technically. It's good to see. I know this is an ancient thread recently resurrected, but I have been doing a bit of pulley research lately and find some very valid points here on both sides of the issue.

First, I must say the following:

DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING DAMPING

The word is DAMPING.

To damp: To decrease the amplitude of (an oscillating system).

To dampen: To make damp or moist; to make slightly wet.

It is a Harmonic Damper, not a Harmonic Dampener.

Sorry, I am a mechanical engineer who designs structures and mechanisms for a living and that always bugs the crap out of me. Anyone who wants to have technical credibility, take notice. You know who you are.

Z Monster

What about "dampering", like in my post. Does that drive you nuts, too?

reen

Oh yeah, I had a point at one time...

The big wrapup for this whole thread is as follows:

(disclaimer: this is my opinion. It is a technically experienced and educated opinion, but just one man's opinion nonetheless)

A) All of the theory of harmonics and the potential for damage to an engine presented here is correct, and this can be a serious problem for certain engines under certain conditions.

B) I don't think it's worth worrying about with most engines such as ours under most operating conditions. Automakers must make certain provisions for redundant factors of safety to accommodate the greatest variety of users under the greatest variety of conditions possible. Perhaps there's an increased risk associated with circumventing some of these provisions, but in reality it's more likely you'll total your car for some other reason than it is you'll blow your engine due to a pulley swap.

zillinois

iTrader: (6)

Monster, you have 2 holes in your pulley and I have 4 what's up with that I wonder. Automatic or manual trans maybe?

I've been reading about this issue for a 6 months now. If anyone cares, my belief is this; Harmonic resonance in our cranks is temporal. I mean it only takes place at certain rpm levels and for determined periods of time. Those time periods are determined by our driving habits. Everytime I drive, my motor passes through the resonant rpm level at some point. That is all though. You pass through it. Once you accelerate or decelerate out of the resonant rpm level it stops because a new frequency is acting on the crank. Well these short periods of time without proper dampening are probably putting added wear on our engines.

It sounds like the the guy with the airplane propeller was running the motor at a certain rpm level that was right at or near the harmonic resonance level. The rpms did not vary enough. Think of driving your car at 3400 rpms for 5 hours. Not suprising it dropped a rod. Obviously, I am not an aeronautical engineer, but I have flown in commecial aircraft before and with the exception of take off and landing a plane can drone on the same note for hours.

Another thing mentioned before is that by reducing the weight on the crankshaft, with say a lighter pulley, stress will very likely be reduced when not in the harmonic frequency.

Lastly, I have no scientific measurements too prove this idea but it seems very likely that the accessory belts can dissipate and even dampen vibration at the crank pulley.

Everybody has to make up their own mind about it. I personally sleep pretty good at night even with an underdrive pulley on my car.

Just my .02 cents.

reen

zillinois, that's what I was trying to get across.

Good "real-world" asessment of the situation.

The holes you're seeing (2 vs 4) are there for balancing the assembly. Look at your flywheel (or any rotating part for that matter) and you'll see similar features. Everyone's will be a little different.

infidsg35

iTrader: (2)

So UR doesnt have any R&D??? I dont like that 1 bit if its true.. Im not sure if thats a fact or someone just saying it. But if its not true then while in R&D wouldnt they know or have the knowladge that if it was sooo important that would of added Harmonic Damper for safety? Im sure it wouldnt of added that much weight or increased the width that much..

Bahhh after all this im still more confused then ever..