Lightweight crank pully

[rush0]

Is it not worth it? I got one, but now im scared to install it because im afraid it will underdrive the oil pump, but I hear its good for boost. I have a fidanza flywheel and I love it.

[WDRacing]

I've never heard of oiling problems, just balance problems...

[:: orion ::]

...and I think the balance problems are all speculative. No hard evidence of any real issue...just a bunch of "I heard" and "my buddy said" and "my dad swears that"...

But as for underdriving the oil pump...NO.

Oil pump is driven internally, NOT by the belts.

- Brian

[Def]

It's not a balance problem - it's a harmonic vibration problem and it does exist. I say that with complete certainty as an engineer.

Your crankshaft has a natural frequency just like a tuning fork, and the stock crank pulley has a rubber bonded section which twists back and forth to cancel this vibration. Going to a solid pulley basically lets these vibrations go unabated, and can potentially cause engine problems.

You can actually hear the crankshaft "ring" at a certain RPM in long crank BMW inline 6 engines with a solid pulley(I had one on my M3). That said, it doesn't underdrive the oil pump, but can cause damage to it over time due to the vibrations.

My take is if you're going for big power NA then it's worth the risk since power is so expensive and hard to come by. If you're FI, then don't bother with a solid crank pulley since more power is just another psi away.

[UncleBen]

I was thinking about getting one, but I can see what you are talking about Def....if I want more power, just more boost....hmmm

Definately getting a lightened flywheel though.

[sil80drifter]

Balance EVERYTHING together. The best thing for rebuildign an enginee, is to get the lightened pulley set, lightened flywheel, and whatever else parts you get, like pistons and rods, and then balance the whole assembly. Then there will be no harmonic issues and you'll get the lightweight assembly which is better than a similar heavier one, if balanced.

sil80

[Nismo_Freak]

Balance EVERYTHING together. The best thing for rebuildign an enginee, is to get the lightened pulley set, lightened flywheel, and whatever else parts you get, like pistons and rods, and then balance the whole assembly. Then there will be no harmonic issues and you'll get the lightweight assembly which is better than a similar heavier one, if balanced.

sil80

Not quite, you have two forms of harmonics. One is the centrifical ocillations caused by RPM, the other is the flex the crank undergoes during the power stroke. It is that flex that is absorbed to some degree by the crank pulley.

However you want to take it... at least in the SR20 community they have been used for years in racing engines that last a full year with no problems running lightweight flywheels and crank pulleys at around 8500 RPM.

[sil80drifter]

yeah when I said no issues, i meant less issues, since balancign the whole assembly reduces individual part flaws. of course harmincs are still there, but they are no longer as damaging, since they have been balanced at/beyond the max rpm you'll ever go to.

A flywheel will go a much longer way than a pulley set to make your car rev quicker (even if the weight reduction amount is stil same, the flywheel has it distributed over a larger area, so any reducations of a weight on a large circle, will be mroe effective than those on a small circles(i.e. pulley)).But, from what I've seen and heard, unles you have serious HP losses, lightening the assembly in any way will result in driveability issues, as your engien revvs down very wuickly (and up it revvs wuickly also), and you'll have stalls and jerks and unwanted wheel spinns, as you have to closely control/match the RPMs when you take off, shift, etc.

sil80

[rush0]

Thanks guys, I think im just gonna sell this thing, since you all scared the hair off my balls =p. j/k Im more than happy with the gains from the flywheel, ill limit my lightening to that alone.

[D-UNIT]

But the stock pulley is undamped too. It has a rubber collar yes and I'm sure it helps "some" , but it is not a damper. Don't forget about the underdrive capability of the lightweight unit there is a 3-12 hp gain right there. Also If your really crazy about damping , Fliudampr makes a real one for our app. "I think".

[Fulcrum]

That little bit of rubber on there does more than you think. Take a tuning fork and wrap the smallest rubber band you can find around the end of it. Even that little piece of rubber will keep it from making sound.

I've seen several D16Y8's and D16Z6's that were running 1-piece lightweight pulleys for more than a few thousand miles. Every one had oil pump and #1 bearing damage. I didnt run one on my D16Y8 and I could still see the factory crosshatch on the bearings. Honda crank pulley's are the same as Nissan; just a little strip of rubber.

The gains you can get from lightening a crank pulley are minimal because of it's small diameter. You can achieve the same gains by shaving less weight off of the flywheel. To underdrive accessories just run underdrive accessory pulleys.

Keep the crank pulley stock or just dump the accessories (except alternator) and have a machine shop mill off the extra grooves for P/S and A/C. Get the pulley rebalanced and you're gtg.

For an FI car I wouldnt even bother unless I was in an all out quest to squeeze the last drop of power. For me, the potential downside is just too big. The money could be better spent on port work, extrude honing the manifold, better tires, etc.

PS I know this is a Nissan forum but the concepts are the same. So no flaming cause I said the "H" word.

[HolyShiznit]

I really dont' understand what the big hype is. There are so many KA's/KA-T's/SR's running aftermarket crank pulleys with no negative side affects. Big one, on this board too, is Orion. He has had his ASP pulley since day one. His car has been running for at least 2 years with it if I can remember right. No problems. And forgive me for saying so but the engines are entirely different, those jokes of automotive mobility (Honda) and specifically their SOHC motors can absolutely in no way can be compared to a Nissan. I have seen those things shatter to pieces if you look at them weird. Adding boost to the picture makes them fly apart at the seams. *shrug*