Engine balancing and the flywheel/pressure plate assembly

[1SickZ]

Balancing is great, but it doesn't keep the flywheel bolted to the Crank...

Does everyone forget about the factory flywheel bolts on there 400+hp set-ups?

[Jason84NA2T]

1SickZ wrote: Balancing is great, but it doesn't keep the flywheel bolted to the Crank...

Does everyone forget about the factory flywheel bolts on there 400+hp set-ups?

Have not forgotten, just always used new OEM myself. I've not heard of an issue relating to flywheel bolt failure, nor have I had any issues. I closely inspected the flywheel I just pulled off which has been on the car making about 500bhp for the last year or so. It looked just like when I put it on. I checked the bolts for bend and stretch, of which there was neither. Should I have a reason to be worried about their strength?

[floridaZ]

[quote]Jason84NA2T wrote:

Balancing is great, but it doesn't keep the flywheel bolted to the Crank...

Does everyone forget about the factory flywheel bolts on there 400+hp set-ups?
*snip Should I have a reason to be worried about their strength?

No, the bolts should be able to hold more than the engine itself, before you factor in heat and vibration. But from my experience with engines (mainly 350 Chevys) the heat and vibration shouldn't even have that big of an effect on the bolts. Unless somebody really stupid sold you bolts designed for a different (read: cooler) heat range it should be good.

Now there is a chance that the bolts could shear. If you have ever seen somebody lose a non-hubcentric wheel, you would know how this happens. And if this should occur, I think a bolt shearing will be your smallest problem, considering how a properly functioning tranny/clutch/flywheel shouldn't move in a way that would cause shear.

[got boost?]

Just to clarify, maybe "harmonic balancer" should be referred to as harmonic damper because using the term "balancer" apparently confuses many people as to the function of this component. Think of it this way, a normal coil spring on a car has to have a damper (called a "shock absorber") not only to make the ride more comfortable, but also to ensure that the spring itself never experiences its resonant frequency where catastrophic failure would likely occur. The crank shaft is a torsion spring which is excited by the forces of the individual connecting rods. In order to prevent damage to (catastrophic failure of) the crankshaft (either over time due to fatigue, or suddenly, due to exciting the crankshaft at its resonant frequency) a harmonic damper is used. This typically has an outer (circumferential) weight isolated from hub by a flexible layer of rubber. This allows the hub (which is attached to the end of the crankshaft) to move slightly relative to the outer weight. People who remove the damper to use the UR pulley really are making a mistake if they think there is no serious tradeoff for doing so. In fact, judging from the wrong information on the UR website, the company who sells these pulleys does not have any understanding of the function of a harmonic damper (or they are intentionally trying to mislead their customers).

http://en.wikipedia.org/wiki/Harmonic_balancer
http://en.wikipedia.org/wiki/Harmonic_oscillator
http://en.wikipedia.org/wiki/Mechanical_resonance
http://en.wikipedia.org/wiki/Resonance

[G-E]

perhaps you would understand that the harmonic balancer balances the pulleys attached to it, not the crank or anything else

the silly thing is you can remove the weight ring from the balancer and you will be out of balance a maximum of 2 grams at very close to the center of the crank, meaning even moderate imbalance on the pulleys wouldn't lead to premature engine wear or destruction.... we know the average clutch is out more than that with a much larger radius amplifying the wobble

[got boost?]

G-E wrote: perhaps you would understand that the harmonic balancer balances the pulleys attached to it, not the crank or anything else

the silly thing is you can remove the weight ring from the balancer and you will be out of balance a maximum of 2 grams at very close to the center of the crank, meaning even moderate imbalance on the pulleys wouldn't lead to premature engine wear or destruction.... we know the average clutch is out more than that with a much larger radius amplifying the wobble

This post makes no sense (and is wrong anyway), re-read what I posted because you still don't understand. The harmonic balancer/harmonic damper/torsional damper/vibration damper/etc. does nothing but dampen torsional vibration.

[G-E]

yes ok I meant that it only affects the pulleys, the belts and pulleys do tend to wobble and jiggle a bit and the "free weight" will oppose that like a gyroscope.... maybe damper is a better word, but we are balancing it in a way to mitigate the vibrations

[SATAN]

G-E wrote: yes ok I meant that it only affects the pulleys, the belts and pulleys do tend to wobble and jiggle a bit and the "free weight" will oppose that like a gyroscope.... maybe damper is a better word, but we are balancing it in a way to mitigate the vibrations

WHAT???????

Wait, you are saying the only reason a harmonic balancer was invented is to offset the "wobble" of the other pullies on the engine?

G-E it appears as though you STILL dont understand what a harmonic balancer does. I refuse to believe this however for the simple fact that it has been brought up MANY times and all the times I remember it being brought up, you posted in those topics as well. However, you seemed to disagree in those topics too.

Three things that should be known to all about harmonic balancer's ARE...

A harmonic balancer is NOT designed for taking up "wobble" in a series of pullies.
A harmonic balancer is NOT designed to externaly balance a rotating assembley.
A harmonic balancer IS designed to balance the engine harmonics (torsional vibration) created by the power stroke of each cylinder.
http://en.wikipedia.org/wiki/Torsional_vibration

[SATAN]

got boost? wrote: Just to clarify, maybe "harmonic balancer" should be referred to as harmonic damper because using the term "balancer" apparently confuses many people as to the function of this component. Think of it this way, a normal coil spring on a car has to have a damper (called a "shock absorber") not only to make the ride more comfortable, but also to ensure that the spring itself never experiences its resonant frequency where catastrophic failure would likely occur. The crank shaft is a torsion spring which is excited by the forces of the individual connecting rods. In order to prevent damage to (catastrophic failure of) the crankshaft (either over time due to fatigue, or suddenly, due to exciting the crankshaft at its resonant frequency) a harmonic damper is used. This typically has an outer (circumferential) weight isolated from hub by a flexible layer of rubber. This allows the hub (which is attached to the end of the crankshaft) to move slightly relative to the outer weight. People who remove the damper to use the UR pulley really are making a mistake if they think there is no serious tradeoff for doing so. In fact, judging from the wrong information on the UR website, the company who sells these pulleys does not have any understanding of the function of a harmonic damper (or they are intentionally trying to mislead their customers).

http://en.wikipedia.org/wiki/Harmonic_balancer
http://en.wikipedia.org/wiki/Harmonic_oscillator
http://en.wikipedia.org/wiki/Mechanical_resonance
http://en.wikipedia.org/wiki/Resonance

I'm sure that they know exactly what they are selling. I am sure they dont care either. I am also sure that there are hundreds if not thousands of people out there who have emailed, called or whatever telling them the mistake in doing this. The fact remains that... People will do what somone who "know what they are talking about" says to do. IE unorthodox.

Its just like all the old hotrod guys I talk to. They all think they know everything cause they have been "doing this since before I was in diapers". When the reality of the situation is that their arrogance blinds them.

And now its rant time again...


The other day, I had shut my car off from lunch break. It was off for a few moments when the old hotrod guy (friend of my companies owner) come to look at my car. So I open the hood and exlaimed "wow, the turbo is still spinning like a minute later!" He tells me " Oh yeah those turbos will spin for 5 minutes after you shut a vehicle off. I say "Well mine is still spinning because it is a ball bearing turbo and the journal bearing turbos that I am used to dont spin as long." He says well one day when you're ready to start playing with the BIG BOYS those turbo's spin REALLY REALLY fast! Thats why you have to let them cool down for 5 minutes before you shut off the vehicle"

I just say "ok" and close my hood. What gets me is that he is saying this while he is looking at a 1000hp turbo in my engine bay and he is saying "when you start to play with the big boys". Dude! Its a 42R they dont get a whole lot bigger. That and everyone knows that the bigger the turbo is, the less RPM's it is capable of spinning, due to the fact that the tip of the blades should not go super sonic. Other wise lots of extra heat is produced. That and bigger turbos dont require longer cool down sessions because of the fact that they spin faster. GOD DAMMIT PEOPLE PISS ME OFF!

Bah, rant over.

[G-E]

satan we aren't disagreeing, it's just semantics.... if you are damping the power pulses or the random banging/wobbling of stuff on the engine, you are doing the same thing, but as it is always spinning. part of any lateral vibration transforms into torsional vibration/movement as well.... the reason for doing it might be different between applications but the mechanics ar ethe same, it's just a slightly compliant flywheel