Solid crank pulley

[wilbo666]

do the cars with damped flywheels also have damped pulleys? or solid?

JZA80 2JZGTE with 6spd / dampened flywheels uses the same crank pulley (dampened) as other 2JZ...



Most cars that come with damped flywheels would have an auto as well as manual option however, so they would need a damped crank pulley for the auto version anyway one would think...


Cheers
Wilbo

[clubagreenie]

For the record, the turning point in fitting the UZ was finding the balancer outer pulley sheared off the rubber dampner section. Although it had been like that for a while. Just sounded like belt squeal. There were no markings on the front of the engine if it moved back and it didn't move fwd enough to fall off.

[oldcorollas]

some good info guys keep it coming!
i think the next step is to speak to an engine balancer and ask if the dynamic balance will get rid of these crank breaking harmonics. from what i have read this seems to be the #1 issue with an undampened pullley

balance =/ harmonics.

[AdrianS]

balance =/ harmonics.

+1 what he said

Consider a single cylinder 4-stroke.
On compression, the flywheel is pushing the piston up,therefore the crank is slightly twisted in one direction by the torque required to overcome compression.
On the combustion stroke, the piston is now driving the flywheel, so the crank is twisted in the opposite direction. On the exhaust and inlet strokes, the flywheel drives the piston again, but with less force required. This twist/untwist occurs on every revolution. If the frequency of twist/untwist (RPM) matches the natural (torsional) frequency of the crank, the crank will resonate in time with the twisting/untwisting forces, which can amplify those forces to the point the crank breaks. Think of pushing a swing and it rising higher each time. This can happen to a perfectly dynamically balanced crank.
Resonant frequency depends on mass, geometry and stiffness of the crank/flywheel/pulley assembly, and is impossible to eliminate. All you can do is move the resonant frequency around in the rev range. If you can design the crank with a resonant frequency above the redline, all is sweet.
The harmonic damper is tuned to match the resonant frequency, and absorb enough energy (at that frequency) to avoid a build-up of torsional vibrations.
ps I've simplified things slightly, by only considering first-order harmonics and a single cylinder. As far as I know, the Merlin v12 of ww2 fame had a lot of issues with torsional harmonics and broken cranks in the design phase.

Here is an brief write-up on the subject http://www.epi-eng.com/piston_engine...on_engines.htm,with a discussion of harmonic damper types here http://www.epi-eng.com/piston_engine..._absorbers.htm

[Q-Authority]

I think many people mistake 'harmonic balancers' and modern day crank pulleys, which have vibration isolation layers built into them, as being one and the same thing. I've done a bit of research on this, as it tends to come up often, usually by those repeating horror stories that their friends, or friends of friends, have had at some point. If solid crank pulleys, and such, were really anywhere near this bad for a motor I really doubt that they would sell as well as they do.

The following, I think, explains the differences fairly well, and is copied from the FAQ, at motorexonline.com:

"4) "Is my crank pulley a harmonic/torsional/vibration damper or a harmonic balancer?"

People are getting their crank pulleys confused with the harmonic dampers found on some V6 / V8 engines. "Harmonic Balancer" is a term that is used loosely in the automotive industry. Technically, this type of device does not exist. The "balancer" part comes from engines that are externally balanced and have a counterweight cast into the damper, hence the merging of the two terms.

The pulleys on most of the new import and smaller JDM engines have an elastomer (rubber ring) incorporated into the pulley that looks similar to a harmonic damper. The elastomer in the OEM pulley serves as an isolator, which is there to suppress natural vibration and noise from the engine itself, the A/C compressor, P/S pump, and alternator. This is what the manufacturers call NVH (Noise Vibration & Harshness) when referring to noticeable noise and vibration in the passenger compartment. It is important to note that in these applications, this elastomer is somewhat inadequate in size, as well as life span, to act as an effective torsional damper. If you look at the pulleys on some of the imports there is no rubber to be found at all. NVH is variable and unique to every car. NVH will increase with the installation of an aftermarket intake and/or exhaust, for example. Think of OEM intake systems in newer cars, they use baffles and resonators in the intake to quiet all the intake noise. Aftermarket intakes eliminate these resonators and create dramatic increases in engine noise from the throttle opening and closing. So to most tuners, certain types of NVH can make the driving experience more enjoyable.

The purpose of a traditional harmonic damper is to protect against crank failure from torsional movement. This is not necessary in most modern engines because of the many advances in engine design and materials. Factors such as stroke, displacement, inline, V configurations, power output, etc., do determine when and how these harmonics and torsional movements occur.

Again, there is a lot of internet hearsay about the pulleys. When engine problems occur, too often people are quick to blame the pulley first, rather than taking the time to look logically into why there was a problem."

If one has had a serious issue with their crank, or such, when using a solid pulley, I would suggest they look more closely at the overall quality of the pulley that they used. They should have absolutely no play in the pulley to crank fitting and none in the keyway fitting as well. Even marginal play in these areas can be extremely dangerous over time. Also, if in doubt, have the new pulley balanced before installing it, though a well made cnc pulley probably should not need it. And finally, buy a pulley that has been made of the strongest material suitable. I would be quite suspect of any manufatcurer that didn't list the material their pulleys were made from. Oh, and don't forget to properly torque the crank pulley bolt.

[timbosaurus]

Something I was thinking, is if having a solid pully is bad, why is a solid flywheel completely OK?

[clubagreenie]

Maybe because the pulley has side loading from the belts but the fly is just sandwiched in the clutch assy.

[Sam_Q]

If solid crank pulleys, and such, were really anywhere near this bad for a motor I really doubt that they would sell as well as they do.

tell that to people selling "rear strut braces" for ae86's, or electric superchargers, twirly air things, power up resistors, etc..

not that I disagree with your other points though.

[Q-Authority]

tell that to people selling "rear strut braces" for ae86's, or electric superchargers, twirly air things, power up resistors, etc..

not that I disagree with your other points though.

Ha, ha! There's a difference between bad products, and BAD products!

Buy a solid pulley for the right reason. A solid oversize pulley for a supercharger app can be a great thing, if it is a well made pulley. A solid pulley, as just a lightweight pulley, probably isn't going to produce dramatic results. But these things add up. Reduce a bit of weight here, and a little bit more there, and you start to have something. Buy a solid pulley as an underdrive device, and unless you're offsetting something like an oversized crank pulley, I feel they start falling into the electric supercharger category, etc.

[Sam_Q]

hhahaha, just messing with you

I wish there where some certain answers in this but realistically there is no way for any of us to know for sure is there?

[clubagreenie]

Or front braces on JZA80's with double withbones where the SHOCK TOWER sees little if any (and none I believe would be relevant) side loading

[andrew_mx83]

IMO strut braces are nothing more than something for the ignorant to wank over.

some interesting info there q-authority, cheers


i have now spoken with a number of engine balancers and it seems that all they can do is reduce the harmonic, not eliminate it.

given everything i think i will stick with a factory item. i now have the 5m crank in the 7m block with the timing case on and the difference is under 15mm if i use the 5m-e pulley (which i wanted to use anyway, waaayyy lighter than the 7m once





will machine up a custom crank bolt for it instead to make up the difference. may make it out of chromoly or similar so its nice and strong.




thanks again to all for the help/info. was a good learning curve either way and now i understand a lot more about what goes on in the engine everytime it fires

[Billzilla]

IMO strut braces are nothing more than something for the ignorant to wank over.

On car with a stiff chassis, yes.
But for older types they most certainly help - It's just that not many people build them correctly to get the most benefit from them.
The best way is to have a bar going laterally between the strut tops and another two bars coming from the strut tops, back to the centre of the firewall and they join each other there.

[clubagreenie]

But even an old car with wishbones (Renault 8/10) where there's no loading it's a fruitless addition of weight unless you want to stiffen the shock mounts.

[WDE_BDY]

IMO strut braces are nothing more than something for the ignorant to wank over.

That depends entirely on the car you put them on.

Callum