STILLEN lightweight crank pulley

BlueR32

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?

wstar

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:


Side view:


Rear view:


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:



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.

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370ZDreamer

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.

wstar

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?

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Josh@STILLEN

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.



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



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




400338 - Standard Lightweight Pulley

Phimosis

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.

Josh@STILLEN

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.

Phimosis

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?