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Old 09-06-2013, 05:09 AM   #1
pjq
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Flywheel Clutch Install Torque and Balance

04S 3.2L 6 speed
Installing an existing Luk flywheel, new sach clutch plate and new sach pressure plate.
Following directions of Bentley or Pelican (101 projects) they do not mention the need to balance these parts prior to installation. Spoke with nearby Porsche dealership (4 hrs) and they do not balance these parts prior to installation but they did point out the centering tool must be used and the tightening sequence followed. This will leave you with a balanced unit.

Questions - (1)Tightening sequence for flywheel 1st stage is 23NM then 2nd stage is 120 degree. After tightening to 23 NM in two stages and in a crisscross fashion Then to go to 2nd stage 120degree, is this normally done with the same torque wrench or with a strong bar? Does it matter if it is done in one smooth motion or in two stages (120degree)?
(2) Balancing - I'm trying to understand this better.
Ideally if you opened up your case, before reassembly you would dynamically balance all rotating parts associated with the crank including flywheel, clutch disk and pressure plate, you then should have a nicely balanced UNIT. If after the engine is installed you have to change the flywheel and/or the clutch assembly your balanced UNIT is no more or is this when the recorded bob weights can be utilized to try and attain the original balance? Is this practically done?
Likewise if we have an existing engine assembly that is renewing its flywheel and clutch assembly how important is it to have just the flywheel/clutch assembly balanced? In this situation we don't have control of the complete rotating assembly, we don't know what the engine balance state was. So would it not be more important to use factory spec replacement parts to hope you get it as close as possible to being a balanced unit? In this situation, by just balancing the flywheel/clutch assembly what are we achieveing?

I hope i'm not overthinking this!
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Old 09-06-2013, 06:51 AM   #2
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There are more knowledgeable folks than me around that will probably weigh in eventually. But I'll put my non-expert info out quickly:

Don't use your torque wrench for the +120 as you may damage it. A breaker bar is a better tool to use.

Probably an oversimplification, but the way I look at the balancing is that if you have two things that are balanced individually, the assembly will be balanced when you bolt them together.
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Old 09-06-2013, 12:40 PM   #3
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All good questions pjq, you are thinking, not overthinking.
As Spendy said 1/2" breaker bar with a angle gauge is best. 1/2" torque wrench will work just set it on the highest value, & try for smoothest, continuous,pull.

In order to dynamically balance the flywheel & pressure plate they must be mounted & spun at simulated engine speeds using actual bolts. Easiest way to do this is with the pre balanced crankshaft. Dual mass flywheel is difficult to balance perfectly, but I believe it is the greatest source of imbalance, pressure plates can contribute also but you can't remove much material, so often weight must be added to the light side. Don't forget the front pulley, bolt & washer too. I always shoot for a 1/2oz tolerance or less. After balancing my engine I was amazed at how much smoother it is. With stock exhaust it's boringly smooth & quiet!
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