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Discussion Starter #1
I know everyone will hate me for opening up a new one of these but I have some questions that I would like some info on.

PLEASE PLEASE PLEASE, do not reply in here if you don't have good technical information to add. I don't want this to turn into a debate on which pulley caused your or your friends engine failure.


The main arguement I've herd for the stock pulley is that the pulley has the dampener in it used to reduce a bad frequency or harmonic in the engine. That when a cylinder fires the crank flexes a bit and the dampener is there to help control this flex or help control a bad harmonic/frequency at a certain rpm due to this flex.

I've herd that the dampener is only ment to work at certain rpm(s) and that it's tuned to these rpm's in the design of it. Is this true?

Will changing the weight of a connincting rod or piston, and or changine the compression ratio of the engine change the rpm that the bad fequency or harmonic occurs? If it does will the stock dampener then be affective in it job?

Will changing the weight or metal (steel to alumium) change the frequency/harmonic or the rpm at which it occurs?

It would stand to reason that any flex in the crankshaft would be felt by both the pulley and the flywheel side. The stock clutch disk has undampened springs, it would be my interpretation that the springs would have a effect on the flex since they are undampened. So if you went with a aftermarket clutch disk without the springs in it would this affect the crank or dampener in any way? Or is the pulley dampener there or partly there the dampen the affects of the springs on the clutch disk? If it is there to dampen or party dampen the affect the springs in the clutch disk have, will going with a solid clutch disk allow you to run a undamped pulley with out or with less affect on any potential oil pump or bearing failure?
 

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The main arguement I've herd for the stock pulley is that the pulley has the dampener in it used to reduce a bad frequency or harmonic in the engine. That when a cylinder fires the crank flexes a bit and the dampener is there to help control this flex or help control a bad harmonic/frequency at a certain rpm due to this flex.

This is true - except the elastomeric dampners, while optimized for the worst normal harmonic in an engine reduce and change ALL crank harmonics

I've herd that the dampener is only ment to work at certain rpm(s) and that it's tuned to these rpm's in the design of it. Is this true?

See above - it is optimized to have maximum effectiveness with the worst engine harmonic, but an elastomeric dampner will help ALL severe harmonics. It also change all harmonic frequencies, and even create some new ones, but they are (as a rule) very minor

Will changing the weight of a connincting rod or piston, and or changine the compression ratio of the engine change the rpm that the bad fequency or harmonic occurs? If it does will the stock dampener then be affective in it job?

It certainly can, especially in cases where you are changing the amount of torque the crankshaft is exposed to and/or pushing it beyond its normal rev range. However, as mentioned, the dampener will still help. Not as much as one optimized for the changes, but the changes will probably be minor enough that it won't be a problem.

Will changing the weight or metal (steel to alumium) change the frequency/harmonic or the rpm at which it occurs?

Meaning the metal used for the rods and pistons or the crank? The metallurgy of the rods and pistons won't affect it aside from whatever changes in mass take place. Shouls be very minor. Changing the crankshaft material (obviously not to aluminum) would of course make a HUGE difference

It would stand to reason that any flex in the crankshaft would be felt by both the pulley and the flywheel side. The stock clutch disk has undampened springs, it would be my interpretation that the springs would have a effect on the flex since they are undampened. So if you went with a aftermarket clutch disk without the springs in it would this affect the crank or dampener in any way? Or is the pulley dampener there or partly there the dampen the affects of the springs on the clutch disk? If it is there to dampen or party dampen the affect the springs in the clutch disk have, will going with a solid clutch disk allow you to run a undamped pulley with out or with less affect on any potential oil pump or bearing failure?

The clutch and pressure plate will not affect it except in terms of change in mass in the flywheel assembly. The thing about crank harmonics is that the flywheel is the constant - the side of the crank next to the flywheel really does not experience anything in the way of harmonics. If there was another flywheel mass on the front side of the crank engine harmonics would be almost nonexistant. It is the lasck of a large fixed rotating mass on the front side of the crank that allows it to have so much torsioinal vibration when combared to the flywheel which always turns at a relatively constant speed.

again - I highly reccomend reading the section on engine harmonics in Heinz Heisler's "Advanced Engine Performance" (SAE publication) - he does a much better job of explaining it than I do and you get lots of helpful illustrations and equations to fill in the blanks.
 

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Discussion Starter #4
Will changing the weight or metal (steel to alumium) change the frequency/harmonic or the rpm at which it occurs?

sorry I screwed up, I ment that as;

"Will changing the weight or metal (steel to alumium) of the flywheel change the frequency/harmonic or the rpm at which it occurs?"

and thanks for the food info Boosted2.0.
 

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WAR said:
sorry I screwed up, I ment that as;

"Will changing the weight or metal (steel to alumium) of the flywheel change the frequency/harmonic or the rpm at which it occurs?"

and thanks for the food info Boosted2.0.
Changing the mass of the flywheel will effect the harmonic - the material is irrelevant except for the extent to which the changes in density affect the overall mass.
 

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Discussion Starter #6
Re: Re: New Dampened/Undampened Pulley discussion

Boosted2.0 said:
again - I highly reccomend reading the section on engine harmonics in Heinz Heisler's "Advanced Engine Performance" (SAE publication) - he does a much better job of explaining it than I do and you get lots of helpful illustrations and equations to fill in the blanks.
I did a search on it and I found 2 books by him called "Advanced Engine Technology" by Heinz Heisler but no "Advanced Engine Performance". Do you have the ISBN or a do you know if the book is online?

Thanks
 

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I know that this is not practable but what would be the effect if you were to use a running centre on the crank pully ?
 

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Re: Re: Re: New Dampened/Undampened Pulley discussion

WAR said:
I did a search on it and I found 2 books by him called "Advanced Engine Technology" by Heinz Heisler but no "Advanced Engine Performance". Do you have the ISBN or a do you know if the book is online?

Thanks
Thats it - advanced engine technology (I have it at home not at work - sorry about the mix up)

Its out of print so it may be hard to find a new copy

anyways its this one:

http://www.amazon.com/exec/obidos/t...f=sr_1_1/102-8864514-3392921?v=glance&s=books

and $65 is a good price - I have seen it sell for over $100
 

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Re: Re: New Dampened/Undampened Pulley discussion

Boosted2.0 said:
Boosted2.0 speaks the truth! In a former life I was employed as an engineer by a couple of the big 3 and did some harmonic damper design work. Yes, they are indeed targeted at the worst harmonic experienced by the stock engine during testing. That point may change a bit due to lighter or heavier aftermarket components but the overall geometry of the system remains essentially unchanged and the crankshaft itself does not change. The crank is a major factor, the surrounding parts have lesser impact. The damper does work at other points throughout the rev range so it'll still do a great job of damping even with different parts in there.

We don't sell underdrive crank pulleys because of the total lack of damping and the corresponding increase in potential for engine damage. We don't run them on any of our cars either. I've never seen a 1zz or 2zz break because of a crank pulley but 1zz/2zz performance is still in its infantcy. I have seen firsthand two DSM cranks that broke when they shouldn't have, probably because both had undamped pulleys.

The 1zz and 2zz cranks are designed and built very well, I have no concern about either as long as the stock pulley is used. I doubt that crank torsionals have anything to do with oil pump failures- from what I've seen that seems to be more a product of oil starvation.
 

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Originally posted by Boosted2.0
The main arguement I've herd for the stock pulley is that the pulley has the dampener in it used to reduce a bad frequency or harmonic in the engine. That when a cylinder fires the crank flexes a bit and the dampener is there to help control this flex or help control a bad harmonic/frequency at a certain rpm due to this flex.

This is true - except the elastomeric dampners, while optimized for the worst normal harmonic in an engine reduce and change ALL crank harmonics

I've herd that the dampener is only ment to work at certain rpm(s) and that it's tuned to these rpm's in the design of it. Is this true?

See above - it is optimized to have maximum effectiveness with the worst engine harmonic, but an elastomeric dampner will help ALL severe harmonics. It also change all harmonic frequencies, and even create some new ones, but they are (as a rule) very minor

Will changing the weight of a connincting rod or piston, and or changine the compression ratio of the engine change the rpm that the bad fequency or harmonic occurs? If it does will the stock dampener then be affective in it job?

It certainly can, especially in cases where you are changing the amount of torque the crankshaft is exposed to and/or pushing it beyond its normal rev range. However, as mentioned, the dampener will still help. Not as much as one optimized for the changes, but the changes will probably be minor enough that it won't be a problem.

Will changing the weight or metal (steel to alumium) change the frequency/harmonic or the rpm at which it occurs?

Meaning the metal used for the rods and pistons or the crank? The metallurgy of the rods and pistons won't affect it aside from whatever changes in mass take place. Shouls be very minor. Changing the crankshaft material (obviously not to aluminum) would of course make a HUGE difference

It would stand to reason that any flex in the crankshaft would be felt by both the pulley and the flywheel side. The stock clutch disk has undampened springs, it would be my interpretation that the springs would have a effect on the flex since they are undampened. So if you went with a aftermarket clutch disk without the springs in it would this affect the crank or dampener in any way? Or is the pulley dampener there or partly there the dampen the affects of the springs on the clutch disk? If it is there to dampen or party dampen the affect the springs in the clutch disk have, will going with a solid clutch disk allow you to run a undamped pulley with out or with less affect on any potential oil pump or bearing failure?

The clutch and pressure plate will not affect it except in terms of change in mass in the flywheel assembly. The thing about crank harmonics is that the flywheel is the constant - the side of the crank next to the flywheel really does not experience anything in the way of harmonics. If there was another flywheel mass on the front side of the crank engine harmonics would be almost nonexistant. It is the lasck of a large fixed rotating mass on the front side of the crank that allows it to have so much torsioinal vibration when combared to the flywheel which always turns at a relatively constant speed.

again - I highly reccomend reading the section on engine harmonics in Heinz Heisler's "Advanced Engine Performance" (SAE publication) - he does a much better job of explaining it than I do and you get lots of helpful illustrations and equations to fill in the blanks.
See what ahppens when I'm away for a few days, Boosted gets to answer all the fun questions before I do!

Great job boosted, I agree 100%!
 

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here's my question: how do you dampen a pulley with elastomeric dampners? Or is this more involved than any of us will ever need to be?
 

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BTW, to address the flywheel question, I meant to include an example. You'll notice that the damper is the same with the manual or auto trans- they have very different masses hanging off the business end of their crankshafts but a single damper design is sufficient in both cases. I'm not aware of any car that's ever needed a different damper depending on transmission type.
 

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Originally posted by jway83
here's my question: how do you dampen a pulley with elastomeric dampners? Or is this more involved than any of us will ever need to be?

I can explain if you want, but it's something nobody here would ever do. The Vulcanization process is very difficult and better suited to a professional.

You would need to "Hot Tank" your damper to clean it and then furnace cure your damper to relax the molecules in the metal to help shrink them and bring them back to their natural state. This is what is called a "Stress Relief Cleaning".

Then your damper should be "Steel Shot" blasted, then a cleaning and stress reliefing operating again.

The rubber part takes a high pressure injection of a high temperature rated, high strength silicone and rubber elastomer. It is then platinum cured in place (Vulcanization).

The silicone elastomer is capable of with standing 450 Degrees of temperature. with 770 LBS. Per Square Inch holding power.

This process should also include a check for concentricty between the two pieces before the vulcanization process.
 

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jway83 said:
here's my question: how do you dampen a pulley with elastomeric dampners? Or is this more involved than any of us will ever need to be?
The stock pulley already has them. Basically the key is that you have a layer of an elastomer sandwiched between an outer solid mass and the center section. The outer mass being suspended from the elastomer is what actually does all the dampening - its like in the cartoons when the guy starts falling really fast and his head stays behind for a second, then accelerates, catches up to him, and overshoots him pulling him forward - same principle. The torsional vibrations in the cranckshaft caused by harmonics cause irregular acceleration or deceleration of the crank - mostly towards the dampener end of the crank. The outer mass on the dampener, however, has its own inertia and wants to keep rotating at a constant speed. As a result the elastomer deforms sligtly as the crank accelerates or decelerates, consequently dampening the torsional vibration. The act of the deformation correcting back to a normal position is what changes the charcteristics of the harmonic and moves it a few rpm and often creates a new lesser secondary harmonic. (none of which are harmful like the first harmonic was)
 

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good stuff.... how do they know where to put the elastmoer dampner in the pulley?

EDIT: i'm sure this is part of the R&D that they do. I'm wondering if anyone knows the process they go through to get it in exactly the right spot?
 

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jway83 said:
good stuff.... how do they know where to put the elastmoer dampner in the pulley?

EDIT: i'm sure this is part of the R&D that they do. I'm wondering if anyone knows the process they go through to get it in exactly the right spot?
It is a complete boundry layer between the 2 pulley halves - if you mean how far out from the hub center, that all depends on the size and mass of the pulley
 

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Originally posted by Boosted2.0
It is a complete boundry layer between the 2 pulley halves - if you mean how far out from the hub center, that all depends on the size and mass of the pulley
would it not be based on the crank? i figured tuning the pulley to the crank would play a mojor role in the exact placement of the dampner, unless the dampner goes around the cirumference of the pulley...
 

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jway83 said:
would it not be based on the crank? i figured tuning the pulley to the crank would play a mojor role in the exact placement of the dampner, unless the dampner goes around the cirumference of the pulley...
The characteristics of the crank will determine the mass of dampener and the design to some extent, but often engine packaging requirements and accessory requirements will have just as much effect on the overall shape - the engineers just have to figure out how to distribute the mass properly withing the confines required by the packaging.
 

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mainly its just there to reduce engine noise. I changed mine out and now i get a soft whine from the engine bay. Kind of anoying but was greatly reduced when I changed to a gatorback belt.
 

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fastcelicagt22 said:
mainly its just there to reduce engine noise. I changed mine out and now i get a soft whine from the engine bay. Kind of anoying but was greatly reduced when I changed to a gatorback belt.
You have no idea what you are talking about - the harmonic dampener has nothing to do with belt noise.
 
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