Did you read the wikipedia quote above as well? They claim that while harmonic balancers are necessary for integrity reasons on larger V-8s, that newer, smaller-displacement engines (like our 3.7L V6, I would assume) only include damper-like rings to reduce noise, not to protect from failure.

I understand the basic theory going on here: since an ICE is acted on by the pistons in a pulsing pattern at odd angles, there will always be vibrations along the crankshaft, and that at certain RPMs these vibrations might be in tune with the natural harmonic frequency of the crankshaft itself, which would amplify the vibrations, potentially desctructively. I think the question is, in what configurations are those harmonics potentially dangerous? The wikipedia quote seems to indicate that smaller engines aren't susceptible to destroying themselves via harmonics.

i'd hesitate to look at a picture of the crank pulley to decide if it is a harmonic damper.

the presence of elastomer or rubber on the pulley does not necessarily mean that it is required for torsional damping. it is common to have such on the crank pulley just for n/v/h.

to be a torsional damper, the pulley would have to have two rings whose movements are somehow isolated from each other, either by material or by springs. another format could be a viscous fluid in a circumferential cavity within the pulley.

stillen has looked at the pulley, and has said the configuration is not that of a damper. if there is doubt as to his expertise, then the only thing to do is to take one off and examine it in cross section.

Well, I've got my stock pulley sitting in my garage off the car, but I don't think I'm willing to slice it just to settle this. It's actually hard for me to tell the exact composition of the pulley and damper from the outside. There's definitely a very stiff rubber ring on the outer backside of the pulley, but it's molded right onto it in a seamless fashion, so it's kinda hard to tell where metal starts or rubber ends without, again, destructively investigating it.

do you have a multitester? if one side doesn't conduct with the other, one might assume that the rubber layer, separating the two rings completely, may act as a harmonic damper. if they do conduct, i'd bet that the internal composition of the pulley is solid, and thus the rubber would be for nvh.

i'm really just guessing. where are the automotive engineer members of this board?
:confused:

Good point. Using the sharp multimeter probes made it easy to tell which parts were rubber and which were metal too, I think I understand the piece now. It wasn't built like I though it was at first. First, here's some pics from my cellphone:

Front view:
http://www.the370z.com/members/wstar...lley-front.jpg

Side view:
http://www.the370z.com/members/wstar...ulley-side.jpg

Rear view:
http://www.the370z.com/members/wstar...ulley-rear.jpg

The pulley is constructed from two separate pieces of metal which are not electrically connected, but it's not a ring on the back like you would think. The inner part of the pulley (the hub and spokes) is separated from the outer part of the pulley (the outer ring with the grooves for the belt). The circular groove you see in the front and rear views is the layer of (very stiff) rubber between the two parts, as highlighted in red here:

http://www.the370z.com/members/wstar...ley-rubber.jpg

I still don't know if that helps draw any independent conclusion. It's not like the design of V8 harmonic balancers I've seen in the past. Those are generally a solid complete pulley, with a ring (picture like a very large washer with a very large opening) mounted on the backside of the outer diameter, separate from the pulley by a layer of rubber. This could still easily be either a real torsional damper or just an NVH-reduction device to me, given how little I really know about the subject.

You two get a room :)

This is the exact same construction used in Ford V-8 applications. Its a injection molded rubber that is bonded between the inner hub and the outer inertia ring. I deal with the O.E. supplier for Ford's dampeners. That is indeed a harmonic balancer and should only be replaced with a pulley that also is a harmonic dampener, period.

There's a logic error here... just because it's constructed the same as a balancer on a Ford V-8, does not mean that it's necessary to prevent actual engine problems on a Nissan V-6 (as opposed to NVH).

Is there any way we can magically summon a nissan engine designer into this thread and settle this?

i dont know about a nissan engine designer, but RCZ should have this puppy on soon, so time will tell if the mythcial harmonic balancer (or lack thereof) will rape this motor or not.

Say it were necessary to have the dampener. How long before the engine suffers from the lack of one?

someone getting cold feet

Nope, Im still doing it.

Mine's been on for about 3.5 days so far, the underdrive version (hence me having pics of the stock one off the car).

wheres your review wstar, how is it.. whats the butt dyno say? notice any difference in PS, or anything?

My info on the pulley install starts here in my journal: http://www.the370z.com/members-370z-...html#post59072

My apologies.. time has gotten away from me. I have some info that will clarify the OEM pulley and the illustrious rubber center section.. but if you'll give me until tomorrow so I can get with my techs to get everything 100%..

Confirmed my suspicions, and should yours.. I just want to make sure I have the wording right.. didn't mean to ignore a response..

This is a harmonic dampener of sorts, on that point you're exactly right. But it's not to balance the engine, it's to balance the pulley ITSELF.

http://www.stillen.com/misc/stockpulley1.jpg

The factory pulley is NOT balanced, and the dampening employed on the pulley is to protect the engine from the outside influences going inward.

http://www.stillen.com/misc/stockpulley2.jpg

The factory pulley is a rough casting, done this way for cost reasons. To cut the entire pulley out of 6061 billet aluminum and balanced is an expensive proposition. They chose to cast the pulley, and add a rubber insulator to act as a dampener. Some other things can assist in dampening, the rubber belts and tensioners in the serpentine belt can help with NVH, and suitable when using a balanced pulley.

You can see the differences in the quality of the part...

400370 - Underdrive Pulley

http://www.stillen.com/misc/400370_s...70z_pulley.jpg


400338 - Standard Lightweight Pulley

http://www.stillen.com/misc/400338_s...ulley_370Z.jpg

Good info, good to know, glad I have one.

Not to the level that they would run it without adding the extra security of the rubber ring.. yes

I really want to see some dyno results for the lightweight crank pulley. I'm almost certain I'll be getting one after I get my exhaust.

Hey Skorch, where you having all your work done ? DIY ? planning to track it ? would love to see another 370 at the next NASA event !! :)

So far I've installed the CAI myself and the HFCs with the help of my buddy. He used to be a mechanic at Lexus and has a very nice selection of tools, so I have him help me with the more difficult installs.

As far as tracking, I've never done it before so I wouldn't even know where to start. I've only taken my previous cars to the drag strip but never to an actual race track. I figure it would be fun to do though.

You're in for a treat ! First timers get lots of coaching and support - it's real easy to get in to... all you have to do is sign up for the next NASA event at PIR (phoenix international raceway, where nascar was a couple weeks ago) and show up... You would be in HPDE1 which is a student run group... there is almost no passing allowed... instructor at all times... very safe... you just need a helmet, but can borrow one if needed

here's an email about the next even from our regional nasa director in az

there are other clubs too of course - like pca, bmwcca, etc, but this one is the best to start with if you're in a nissan

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Anyone have dyno numbers before and after for the Stillen crank pulley, yet?

I'm still skeptical and don't want to buy any unproven parts because my funds are limited and I'm saving my money for an electric supercharger. ;-)

It makes sense why the underdrive pulley increases dyno numbers, but not the lightened stock diameter pulley. My logic is that if SRM can blip the throttle from 3,000 rpm to 6,000 rpm in under a second, then a 6" pulley with a moderately lower moment of inertia shouldn't significantly alter the ability of the engine to rev from 3,000 rpm to redline over the course of a 25 second, fifth gear dyno pull.

No offense intended, but this sounds like you guys made up this logic to sell your product.

The post starts by saying it IS a harmonic damper. But... Goes on to say that the rubber is put in this 6" cast pulley to protect the engine from vibration caused by the pulley. If that were REALLY the case, every pulley on the engine would need a similar damper. Small vibrations going in to finely balanced power steering pump would be way more damaging than small vibrations going into a 300 pound engine that has explosions going on inside that apply thousands of pounds of asymmetric load on the crankshaft. The bottom line is that the stock pulley is a harmonic damper and the Stillen unit is not. The vq37 is known for it's poor vibration/harshness qualities at high rpm and the stock damper is there to damp the vibration and harmonic frequencies. It may be true that the engine will survive to it's normal life expectancy without damping those harmonic frequencies, but the engine will be subjectively harsher.

No offense taken. The stock crank pulley is NOT a harmonic balancer for the engine. It does have the ring in it to help with NVH from itself to not go back into the engine (and is the only pulley directly connected to the engine), which is internally balanced. The STILLEN pulley is balanced and extremely precision cut.

There are hundreds of pulleys on VQ37's with no problems, and thousands more on VQ35's.

It's been suggested (and referenced to other makes and models with horror stories) that these are "dangerous" to the motor, but in their application, and due to the precise process that these are developed, these problems just don't exist.

Let me chime in and tell you I've had the pulley on for over a month. It's fantastic. I feel a difference in my throttle response and I can't feel any loss in power from my air conditioner. I drive my car daily and drive it on the track weekly. It's an inexpensive mod that you will be able to enjoy the results.

Also, the engine is a lot less harsh at the higher RPMS since I added my stillen exhaust and intake.

You and I have the UD pulley though. Phimosis' skepticism is directed at the lightweight pulley from Stillen that's stock diameter, not the one we have.

Something is fishy here. The picture of the crank pulley that Wstar and the picture of the crank pulley that Josh at Stillen posted both have holes drilled on the back side of the inertia ring of the damper, but the holes are at different positions. This indicates the pulley IS balanced. It is a common technique to spin the object, then drill holes to remove metal, drilling the holes deeper to remove more metal as needed, to balance the rotating object.

For a better explanation of whether this is, or is not a damper, read the article by Steve Dinan, of Dinan racing:

http://www.dinancars.com/bmw/technia...armonic-damper


Also, the response from Stillen didn't adress my primary arguement, that if the pulley needs to be damped to prevent the pulley from damaging the engine, then every other pulley needs to be damped to prevent damage to the water pump, alternator, AC pump and power steering pump, but they are also cast units that do not have rubber dampers. I swear you guys rationalized your logic after you built the part. Show me some evidence that your argument is correct. Maybe some whitepapers from Nissan?

You're absolutely correct.. I should have been more clear.

The stock pulley is balanced via the removal of material, but is not a harmonic balancer.. please forgive my mistake. But no where near as precise as a billet cut CNC'd piece, hence the NVH ring in the center. You couldn't have it be just the pure cast piece with slag hanging off different areas.

so to simplify all this stuff for newbs like me. if i get the lightweight one, WILL IT HURT ANYTHING?

PS.... The reason I am taking such a critical eye on this issue is that I really want to put a lightweight pulley on my Z..... I'll do just about anything to make it faster and it already has a plethora of Stillen parts on it. I just want to make sure I understand the risk/benefit ratio on each piece before I take the plunge.

Curious on why lightweight vs. U/D for you Phimosis?

(and thank you for your orders.. you're practically a rolling STILLEN billboard!) :D

Maybe he's planning to SC in the future?

I kinda am too, long term, but given the cost and complexity of the SC install, it's not like it would be a big deal to swap the pulley at the same time.

I still havent installed mine, I may swap it with a UD one.

LOL..... I'm waiting for that damn supercharger!

So am I! You have no idea. I get to see the progress and can't talk about it.. :D

Aw...sure you can, Josh. We'll be discreet, won't we guys? :rolleyes:

I'm not saying that some lucky owners that came by picking up product and got the tour haven't seen our progress.. but they signed a release to give up their car if they spoke about it to the forums..