jtgli

iTrader: (13)

I havent really searched but I would like to know about the lightened crank pully for the Z. Does anyone know if Nissan harmonically balances the crank pully with the crankshaft? Does anyone have a crank pully and had it for some time? Have their ever been any probs with rod bearing or any other failure due to the crank pully? All help would be appreciated. Lastly would there be any noticable gains with the pully on the Z? Thanks

Triji

iTrader: (2)

I wouldn't really reccomend it... Not worth the risk and yes, the stock is harmonically balanced to the crank.

PULLEY



KEY





Here is a good link to read up on... Only aftermarket pulley I would even consider now is the Fluidampr...

http://g35driver.com/forums/showthread.php?t=112603

MustGoFastR

iTrader: (13)

Start there.

Cannysage

iTrader: (29)

I have about 5k on mine and it's perfect.. no sqeaks, no prob. There are no harmonic balancer on the z, or new import cars in general..

JhayRCruz

iTrader: (5)

ive also had my crank pulley for 8 months and its runs perfect!

Machupo

iTrader: (6)

the stock pulley is not included in the harmonic balancing therefore you will not throw anything off with an aftermarket pulley... i have over 25k of hard driving on mine with no issues whatsoever...

Zincognito

iTrader: (2)

so what pulley is the one pictured?

SpeedRcr

iTrader: (5)

Looks like a UR pulley...the VQ is internally balanced. There has been debate still about the stock pulley absorbing some lash back...ive put on 30k miles on my pulley with no issues belts are as good as when the car was new, still the first set of belts at 61,500 miles

davidv

iTrader: (2)

I believe you.

davidf

iTrader: (18)

Is fluidamper considered a light weight pulley?

Resolute

iTrader: (2)

Yeah this debate will continue on forever I'm sure. As I've posted before, and has been discussed before, there is no such thing as a harmonic balancer. There is such a thing as a harmonic damper. That is what lightweight pullies are lacking. Everyone seems to interchange the term damper and balancer. Of course the crankshaft is "internally" balanced. Big deal. Older engines used to have a mass on the end that was to help balance the rotation of the crank to compensate for poorly machined cranks. Ours is machined well enough, as any modern crank is, that it spins on its own axis without wobble -as it should. So, it's "balanced". If all the damn thing had to do was spin without anything acting on it then it would be fine. However, it has to take the torsional stress of pistons pushing it around. The pistons do so in a set frequency. That term frequency is important. Our 60 degree V6 has a frequency of a power stroke occuring once every 120 degrees rotation to complete the entire firing sequence over the course of two full rotations (since it's a four cycle engine). Besides the frequency of the power strokes applying torque about that spinning axis, there is the issue of inertial loading also applying torque about the axis. These are the only two forces acting on the crank. Since we are dealing with a four cycle engine, there are half order as well as full order frequencies involved. The damper on the end of the crank is designed to disrupt those frequencies by, get this, dampening them. The little rubber piece prevents the frequencies from reaching the natural harmonic frequency of the block, the crank, etc.. and causing things to break. Imagine if your car had no dampers and the springs just occilated up and down. If the front and rear springs hit the same frequency and do so in harmony with each other, the car would buck like crazy. The same phenom happened with "Galloping Girdie" the Tacoma Narrows bridge in Washington. The wind caught the natural frequency of the bridge cables and they snapped. The same thing happens when an opera singer belts out a tone and breaks glass. The frequency of the glass is the same as the singer's, and the molecules are broken apart at stress points in the glass when their movement is amplified by the harmonic. The same can happen, and has happened, to crankshafts. This is why you don't see professional teams running lightweight pullies that lack a harmonic damper. Hell, there are pictures of the VQ35 used in the GT300 class as well as the VQ30 in the GT500 class on this forum, do a search. Neither one will have a lightened pulley on them. The crank and pulley may be balanced, but engine harmonics refers to the frequency of force acting on the crank, including the oft neglected but far more devastating imaginary forces of inertia, and their relation to the natural frequency of the material they act upon. This is pretty simplified for what I had a whole semester on in college, but if you really want to blow your hair back on just how deep this rabbit hole goes, check out a widely available book by Den Hartog, MIT prof., called "Mechanical Vibrations" for further review.
Will

Resolute

iTrader: (2)

No, it's heavier than stock.

Machupo

iTrader: (6)

Ok, so what's the magical frequency that will break my engine? I'll remember not to cruise at it for hours...

intoxicatedpete

iTrader: (11)

How much heavier is the Fluidampr than the stock? I tried searching but was unable to find it. I know the KJR pulley weighs at 2.04 lbs.

EDIT: So the Fluidampr is 7.22 lbs (http://www.fluidampr.com/NISSAN.htm).
I contined my search and found that the stock pulley is 6.5 lbs (https://my350z.com/forum/showthread....+pulley+weight)

Can anyone confirm the stock pulley weight?

caucasiancoupe

I had my stock pulley actually do that. Ill post a pic tommorrow.It did not do any damage. Thank goodness.

caucasiancoupe

My crack in the pulley is very little compaired to the other posted pic. But dam that thing wobbled.

bofa

iTrader: (23)

Is that a no?

Resolute

iTrader: (2)

Not really.
The crank is obviouisly "balanced" as everyone says. But balanced does not mean there are no other forces acting on the crank that cause vibrations. This is obvious just looking at an idle engine vibrating in the engine bay, or with your hand on the shifter you can feel the vibrations. Vibrations are just a type of periodic motion. The pistons pushing on the crank and inertia pulling on the crank form the most obvious periodic motions. In other words, these are motions that occur in a repeated pattern. Some periodic motions want to cause the engine to buck on a lateral plane, others act on a vertical plane. All these periodic motions are seen as vibrations, and some are called harmonics. They occur over the entire rpm range. Harmonics are just the simplest form of periodic motions. With every engine, some harmonics are automatically cancelled out by each other, so that the net force produced is zero. Some engine designs are better at this than others, which is why straight six engines tend to feel "smoother" than V6's. In any engine though, most harmonics are not cancelled out and are transferred through the crank. The harmonic damper is that elastomer ring in the pullley designed to help eliminate some of the more devastating harmonics that transfer to the crank by cancelling them out. Lighter underdrive pullies that lack this elastomerr ring will not cancel out these harmonic frequencies. People that say otherwise are wrong.
Now, that doesn't mean that your engine will destruct in a vibrating blaze of glory if the damper is removed. The fact is, your engine also damps these periodic motions through the dual mass flywheel and output shaft on the manual transmission cars. The auto cars fare even better as the torque converter is a massive fluid type damper in and of itself. The purpose of the elastomer ring and steel pulley is because with some calculation, an engineer can determine the specific "best" frequencies to dampen, not all of them mind you, just the most critical frequencies, and construct the damper accordingly. This is a good bit of protection for the bearings, engine mounts, etc over the course of the engine's life. Makes sense for the manufacturer to place it on the engine. Removing it will most likely lead to extra wear over the long run, but nothing too disasterous in and of itself. Combined with a lightened flywheel, these harmonic frequencies can get worse, placing more wear on the engine. Also, those people making really big power or revving higher have increased the intensity of the two forces acting on the crank: torque from compression and inertia. The greater these two forces, the greater the harmonic amplitudes can be, and the more neccessary damping them becomes. Hence, the use on racing engines with high revs and big power. Some professional drag shops have even seen power gains with a slightly heavier damper over lightened crank pullies, because at some point the power freed by the reduction in rotating inertia is lost by the force needed by the crank to overcome the periodic motions its fighting against. In other words, big power and big revs mean there are big forces the crank has to fight against, and damping them out rather than letting them amplify is good for power.
Having said all that, obviously this is not the case for stock engines, or most modified. I don't like lightened crank pullies as I don't see the marginal gains worth it, but those making big power or revving high should think long and hard about removing the stock damper. Better yet, place a fluid damper on instead because fluid dampers can cover a broader range of harmonics. Sorry for the long wind response, hope there is something salvageable in this for people,
Will

rotaryrocket7

That's good info above, right on the money.

rlwjr1

iTrader: (3)

Maybe this helps explain