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I just had a machine shop take off about 20 thousands of an inch from one of my old flywheels so I could reuse it. Is that too much? I thought I heard that would be ok, but now someone told me that 5 or 10 thousands is the max. I'm not sure if I should use it or if I should buy a new flywheel. Normally I would get a new one, but I just replaced it a few weeks ago and it got ruined due to a faulty clutch install, so I'm not very eager to spend another $450.

-Paul
 

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You're taking a gamble machining the stocker at all... bt you gotta do what you gotta do... Personally I'd make the install shop pay for their mistake.
I know I back up my own work, others should too...
 
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Yeah, I'll definitely try and get them to cover everything.. but I'm not counting on it, at least without suing them first. It would be hard to prove, especially since they already went ahead and took everything part when I said not to. I bet the reason they did that is because they noticed all the pressure plate bolts were loose..
 

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So it's not a good idea to resurface the flywheel at all? It ABSOLUTELY has to be replaced? What's the worst that could happen if I took off 10 thousanths and threw it back in?
 
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Flywheel

So what happens if your clutch is just slipping due to wear, but otherwise it's normal, and you replace everything but the flywheel and you don't attempt to resurface the flywheel. In that case, would it function properly? What are the drawbacks? In the real world, can you get away with it?
 
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Discussion Starter #6 (Edited)
heh, doesnt seem like anyone really knows. I've been told that anywhere from 2 to 20 thousandths is ok. Even 20 thousandths isn't very much... I don't see what the big deal is. I've also been told that it'll start to chatter if you take off that much, but that doesn't make any sense to me whatsoever. .02" isn't can't even be 1% of its total mass.
 
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My clutch is starting to go also. I called MVP and they (forgot who i spoke with) said that resurfacing is not advised because it could damage the bearings or something like that. Only drawback would be loosing a little bit of clutch life.

Chris
 

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Allrighty then, think of the FW this way...
It's a DUAL MASS flywheel, that means there are two separate masses moving around cancelling things out. So you think taking away less than 1% of the mass by resurfacing is no big deal? Well it's not if you took that away equally from both masses, but the second mass you are never touching. That's why it could throw the dual mass effectiveness right out the window. Machining tends to take out tempering and sends alot of frequencey through the metals being cut.
Like I said you could chance it and it may work okay but the Getrags seem to be real touchy.
You might even be better off not resurfacing at all and letting the new disk seat to that not perfect surface of the existing FW, but remember that the FW sometimes wear out and stop dampening on there own already and machining it may just make that happen a little faster as well.

Just try to consider all the possibilities and include time and aggrevation costs into the equation. Once you change out the clutch once you'll probably get to the point when you want to try something else anyway down the road. It's amazing how many clutch setup choices we have for one car...
 
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Discussion Starter #9
theman said:
Allrighty then, think of the FW this way...
It's a DUAL MASS flywheel, that means there are two separate masses moving around cancelling things out. So you think taking away less than 1% of the mass by resurfacing is no big deal? Well it's not if you took that away equally from both masses, but the second mass you are never touching. That's why it could throw the dual mass effectiveness right out the window. Machining tends to take out tempering and sends alot of frequencey through the metals being cut.
Like I said you could chance it and it may work okay but the Getrags seem to be real touchy.
You might even be better off not resurfacing at all and letting the new disk seat to that not perfect surface of the existing FW, but remember that the FW sometimes wear out and stop dampening on there own already and machining it may just make that happen a little faster as well.

Just try to consider all the possibilities and include time and aggrevation costs into the equation. Once you change out the clutch once you'll probably get to the point when you want to try something else anyway down the road. It's amazing how many clutch setup choices we have for one car...
Good post theman, very informative.

Chris
 
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Dual Mass Flywheel

The total mass of the dual mass flywheel is optimized from the factory to lessen and dampen natural engine harmonics. Buy adding and subtracting mass and altering stiffness values, engineers can modify and shift and tune bending modes in a measured and concerned axis. Peaks or bending mode shapes are identified buy measuring acceleration rates. At various frequencies each part has a contribution to total stiffness and mass and are all dependant of one another in a system. The total free wheeling mass of the flywheel in a non-coupled state has not changed in total stiffness or mass. But buy coupling up the transmission, the dynamic modal stiffness values of the system + flywheel and transmission change to a completely different state. This transition state is designed from the factory to add rotational mass and stiffness at a predefined slope to help dampen rotational shock loading, offer longer life, and add good sound NVH characteristics.
On a fixed tuning fork you will always get a predefined frequency in which it resonates. If you where to take mass out and keep the stiffness value the same, the frequency would always rise and hence shift the resonating frequency mode. Mass and stiffness values along with other variables, shift modes. If you have two modes that are in phase they are considered amplifiers, and if they are out of phase of each other they are considered dampers. Since the flywheel is balanced, engineers will optimize its mass property because it’s quite obvious that the rotational shear stiffness value is dam stiff between the crank and the flywheel…as you can imagine. Because Force is equal to mass times acceleration, the system should have the same signature through out the reciprocating components rotation cycle from 0 – 360 degree’s. Force will change dynamically and is dependant of all other things…that I’m sure you can imagine. Acceleration is dynamic but is mostly repeatable and should not change from the standard OEM modal alignment.

Adding a lightweight flywheel on the factory 2jz-gte engines is not such a great idea and significantly alters the mass on a relatively long crankshaft. If you purchased a lightweight flywheel and had an OEM or aftermarket crank balanced with the flywheel to with in a half of gram…consider your self “Golden”.

Will a couple of thou off the flywheel change the mode shape?? Maybe a very small increase in frequency…but I doubt that it will cause concern in the OEM modal alignment causing a failure or amplifying another mode.

Will the metal chips get inside the flywheel and change the slope of the engagement? That depends on what type of machining is being done and has been noted on the Mkiv.com doc lists.

If you are running a high horsepower supra with a stock factory engine you will reach a point were you are breaking stock dual mass flywheels…so save your old stock flywheels and have them reground. Then simply clamp the flywheel (with a lot of force) in a big vise and weld the two disc’s together making sure the welds are symmetric.

Drag racers don’t care about shock loading and good NVH characteristics…they just don’t like spinning rod journal bearings!
;)
 

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Im still using my stock fly wheel with over 90,000 miles. Last time I changed my clutch (2 years ago) I simply left it bolted to the car and scuffed it up with a DA. Its been holding fine and I have pushed over 682RWHP with a T72, and now sport a T78. No problems whatsoever.
 
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