Originally Posted by kompressed55

A crank harmonic damper doesn't have dampening "transitional forces between the crankshaft and the SC" on its mission list. That's simply a wrong statement. A far better explanation of the function of a crank harmonic damper can be found at the Fluidampr website:

"Each time the air/fuel mixture inside a cylinder is ignited, the combustion that occurs creates a torque spike that is applied to the crankshaft through the piston and rod. This torque spike is so severe that it not only turns the crankshaft, it actually twists the crankshaft ahead of its normal rotation and then the crankshaft rebounds. This twisting action is known as torsional vibration. When these torque spikes and forces get into phase with the natural frequency, critical torsional harmonic vibrations occur and can be seriously destructive to the bearings and the crankshaft. Dampers are designed to control those destructive vibrations.

Critical harmonic vibrations occur numerous times in a engine’s operating range. Stock rubber and elastomer-type dampers are frequency sensitive “tuned absorbers”, and work at only one critical frequency. In the case of a stock rubber damper, it is tuned for a factory engine’s critical harmonic vibrations. If you change the mass of pistons, rods, or the crankshaft, you change the natural frequency of the crankshaft assembly; therefore, the stock damper is no longer tuned to the new frequency of vibration, and you may be headed for early failure of expensive engine components."

Since the vast majority of us are not modifying the mass of our engines' internals (i.e., pistons, rods, crank), I would assume that the factory damper, and larger pullies based on the factory damper are correctly frequency tuned for our engines (any experts to refute this?). The supercharger happens to be a belt driven accessory which function has nothing to do with the intended function of the crank damper.

Perhaps some tuners not relying on the factory crank damper somehow measured the frequency of the SC belt tensioner damper (didn't know it had one) and determined it could function as the damper for the crank as well. Personally, I would rather have a tuned crank damper (e.g. factory) responsible for controlling harmonic vibration of my engine block, and replace it as needed when the rubber shows signs of deterioration. That's my take on it; maybe others with more expertise can chime in.

Originally Posted by kompressed55

A crank harmonic damper doesn't have dampening "transitional forces between the crankshaft and the SC" on its mission list. That's simply a wrong statement.

Originally Posted by machz990

They see excess weight or rotating mass, can't understand why it's there, and yank it off. What they don't realize is they have removed overall mass from the crankshaft and changed the range of the harmonic vibration to another rpm range. Engine manufacturers have to deal with harmonics when designing motors. They sometimes add mass to the crankshaft to move the harmonic vibration to an area of engine operation that is transitory, in other words you are probably accelerating or decelerating through this rpm but never continuously operate there. Changing the mass of the crankshaft may move the harmonic vibration to a range where the motor frequently operates for extended periods. In a car that might be at 65 mph in final gear.

Originally Posted by jangy

Great post. They also have lots of info on why NOT to use the rubber setups in our OEM ones, but hey..

Originally Posted by jangy

I get what you were saying and am learning, but I don't get why my statement was so simply wrong? I can see that the crankshaft is going to have that vibration, but so what? I ask that because we were talking about the PURPOSE of the dampner. Are you saying that the dampner steadies the crankshaft? If so, then I was off because i doubt that is the case. I nstead, I think the dampner is to help absorb the vibration coming from the crankshaft and send steadier power to turn the SC. Is that not the same as dampening "transitional forces between the crankshaft and the SC"?

Originally Posted by E55 PWR

To get a perfectly balanced pulley you have to start from scratch and CNC machine one.

Originally Posted by kompressed55

Not true. You simply have to balance the pulley assembly as the final step of the manufacturing process. Remember, balanced is balanced - it either is in balance or it isn't.

Originally Posted by Marcus Frost

Balanced is balanced as long as there are no variables.

Originally Posted by kompressed55

Where's the disagreement? I said balanced is balanced. It's foolish to suggest that a CNC based damper is not subject to so-called "variables" over time. I think there's already been at least one post regarding issues with a CNC based pulley. It can corrode too, elastomers can fail, bolts can loosen, etc. Maybe it occurs at a slower rate, maybe it doesn't. Let's be honest here and say that no pulley design is a panacea. Basically, you pick the price point where you want to play, and you go for it. All else being equal, so long as the pulleys in question are of comparable diameter, your engine will get the identical power increase potential.

Since I don't have a pulley on my car (yet), I have no dog in this fight. Just trying to keep things on a relatively factual basis.

Originally Posted by Exotic-metal55

True and not true. Bottom line, they all have variables. The other units have bolt on blower pulley section (6-8 variable bolts) and 40% lighter rotational mass. ASP has 20% heavier rotational mass. Where does that leave us all down the road? Is 20% heavier safer or is 40% lighter safer (My 40% is based on Jangy claiming 4 lbs lighter on his style )??? MB, ASP and others all seem to be CNC-ed in some form or shape.

Originally Posted by Exotic-metal55

Interesting.. Same method of machining as ASP but 4 small pins hold the outer ring? They look like allen head screws or also called set screws. From other pictures, they balance the same way too.


I still like welding verses pins or screws but that is my 2cents..

Originally Posted by Marcus Frost

II don't agree that balanced is balanced if it's more prone to becoming unbalanced.

Originally Posted by kompressed55

I understand your concern, but your attempting to lump two different physical characteristics or properties into one and the physics of your statement are nonsensical.

Either an item is in balance or not. Period. End of statement. Assume two pulleys, one a bolt together design, and the other, a substantially less expensive one that has some welds on it, have each been balanced as part of their respective manufacturing processes. The simple, unalterable fact is that they both are "balanced."

Your concern can actually be expressed as a pully's tendency to lose its state of balance as a result of being subjected to use, and which design style is more susceptible to losing its state of balance over a period of time. That tendency, though it may exist (no one has really documented or actually measured this in any controlled scientific manner that I've read about) has zero to do whether a pulley is in balance or not. It is either is or it isn't.

I would agree that I would be more willing to consider for purchase a pulley that had a documented characteristic of retaining its state of balance over a longer period of time versus one that was more likely not to, but there doesn't seem to be any reliable data available to assist us in analyzing how rapidly a particular pulley's state of balance will degrade. I don't think attempting to extrapolate rate of balance loss from manufacturing method used is much more than an assumption without some actual, verifiable data to support the assumption, but then I'm not an engineer either, so what do I know?

Originally Posted by kompressed55

The damper has nothing to do with the SC other than driving it, so that's why I said the post was wrong. The damper's purpose is about protecting the crank as noted in a few of the posts above. Anyway, that's my understanding of its function based on everything I've read.

Originally Posted by jangy

I disagree with the dampner being there to save the crank. That crank is the hardest metal in the car. Let's say things got jammed up, what is that dampner gonna do? Harmonic distortion, yes I can see but again I don't see that harming the crank. When spinning, the force from the crank is huge and that little bit of rubber isn't even going to save the seal in the front. A dampner or any buffer goes both ways. it is between the crank and the SC and it helps them BOTH survive. But again, if the dampner is so great (rubber or fluid) why would the EVOSport pulleys be doing so well (from a reliability point)? Also, if rubber were the way to go, especially rubber that has been through an extra round of stress, why did RennTech change its design away from an MB hybrid, eventhough they are no longer pushing that market?

Originally Posted by Marcus Frost

jangy,

I don't know if he is referring to the actual crank, or the bearings. I would suspect he is referring to the latter, in which case what he wrote would be correct.

-m

Originally Posted by jangy

But even the bearings would barely be saved by the rubber. Again, i agree with harmonic, but i just don't see how a little strip of rubber will be anything but fully stretched at WOT or even normal runs. Once the crank is spinning, the dampner is just there. it isn't like that rubber is still staying flexible. Also, don't forget that there is already a tensioner there that has lots of give (much more than any dampner) and we are running a rubber belt that is NOT linked on, so it slips. Are you kidding me that we need a piece of rubber to save the crank or its bearings?
.

Originally Posted by MRAMG1

Jangy:

EVERY car built has a Harmonic damper installed from the factory, wether it has a Supercharger, Turbo, or NA. Its SOLE purpose is to control harmonics so that you DO NOT rip up the bottom end of the engine. It has ABSOLUTELY Nothing to do with saving the Supercharger my friend. When you go have a custom engine built, ALL engine tuners will ask you for your balancer. No they do not tune it for harmonics, they simply re-balance it for your new rods, piston, or what ever elese you have added. Even race cars, that build ALL internaly balanced engines will still run a Harmonic damper on them to help save the bearings/crank. Yes, they really help that much. Talk to ANY engine builder and they will help shed some light on why they are needed so badly on ANY engine.

See yeah

PS: Even with New rods, pistons and or a crank, they ONLY re-balance the Harmonic damper. They DO NOT change its frequency/damper range. this is the ONLY reason why I could ever see using a Fluid damper IF you changed ALL of the internal engine components. There just ISN'T that much of a change in the resonant harmonics to warrent changing the frequency of the damper unless you have changed EVERYTHING.

Originally Posted by stevebez

The motor needs it regardless of the S/C drive element. If I am not mistaken the harmonic tuning is islolated from the S/C drive ring by the rubber insulation, so that the harmonics are not affected.

Originally Posted by jangy

I see your point, but again, why did RennTech swap setups and keep the size identical? I've heard much more about fluid dampner than just for race cars, but anyhow. My argument is not that the rubber doesn't dampen harmonics. It is that the rubber is getting stressed during the production of the ASP pulley. And again, I dot believe that small strip of rubber is doing much of anything at high revs, even if every race team has it. Why does the EVOSport setup work?