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Originally Posted by farmboy
what’s inside the dual mass flywheel or is it two separate metal places separated by a rubber adapter? what, per se, makes the flywheel on the 986 a dual-mass type?
it seems curious that i haven’t heard anyone say they eliminated the 3000 rpm vibration by exchanging in an aftermarket light flywheel. it seems such an approach would work as it’s a simpler part; but, i suppose it stands to reason that a new dual mass flywheel would actually have less vibration than a non dual mass aftermarket flywheel.
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The dual mass flywheel is just a heavier weight than a single mass. I'm not sure if there is a different composition inside. It is supposed to make the clutch engage a little slower so the car does not jerk as much and also lowers gearbox noise.
A new dual mass flywheel should have less vibration and noise than a lightweight one while the lightweight flywheel allows the engine to spin the gears more easily for quicker starts, but does not actually "add" power (hp) to the car. The lightweight flywheel is more fun to drive with until you hit traffic, then you get more jumpy starts when your foot starts to get tired and your clutching gets sloppy.
One of these days when it's time to replace the clutch I'm going to put in the lightweight flywheel and I'll report back what happens.
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Originally Posted by farmboy
initially my vibrations seemed related to rpm only - a resonance at 2000 and 3000 rpm. particularly when the engine was cold. but then i discovered that by veering left i could intensify it, and by veering right eliminate it almost entirely. maybe it's one of the side engine mounts? how do i inspect the side mounts? must they be removed for inspection?
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That sounds to me like one of the right wheel bearings or control arm bushings is wearing out. I don't believe a bad engine mount vibration should not be affected by turns. It would change with rpms, the faster the more vibration.
One thing I would like to know is if you put in a lightweight flywheel will your gas mileage increase since the engine does not have to work as hard to get the gears going?