Any fix for lightweight flywheel grind?
 

Just installed a lightweight flywheel and like many other people the deceleration grind from 2k-3k I find quite annoying.

Does anyone know what causes it or if theres anything that can be done about it?

If by "grind" you mean a rattle. Simply it will not go away. This is referred to as "chatter".

Piston powered motors do not run on a seamless power delivery. The pistons transmit power to the crankshaft, then to the transmission, drive shaft etc. in pulses. The tolerances of the connections of these parts in your drive train are not extremely tight because that adds friction. There has to be slack.

The weight of the stock flywheel allows for increased rotational inertia. It's weighted so that between pulses the rate of deceleration on the drive train is minimized. That way when the next pulse is transmitted, there isn't a drastic change in speed that was produced by the last. Pretty much it makes the power band seem "smoother", and decreases NVH at the cost of acceleration.

When you decrease the weight of the flywheel, or other parts of the drive train for that matter, the power pulses produced by the pistons can more effectively be utilized. Quicker acceleration and deceleration due to less rotational mass. But that quicker deceleration causes the opposite effect on NVH. When your engine speed drops the slack that is being taken up every time a pulse moves the parts becomes more pronounced and when it his a certain frequency, "2k-3k", you hear it.

Unfortunately, with every mod, there will be a pro and a con. The con for a lightweight flywheel is chatter.

Hope that made sense.:thumbup:

No not flywheel chatter, I know what that sounds like, grinding. Or very low tune high frequency. Its not a pulse, it almost sounds like a bearing with a heavy load.

Other mods? Transmission bushings? Engine Mounts? I know that in my car, I get all sorts of whines and noises after all the bushings and mounts have been upgraded.

That grinding noise is the chatter we speak of. I have it too and it is exactly as you describe, like grinding between 2k and 3k on deceleration. It's caused by gear backlash in the transmission. There's play between the gear teeth and when you decrease the flywheel mass the angular velocity becomes less fluid and smooth, bringing out the chatter in the gear teeth. The 'fix' for that particular problem to run a heavier flywheel unfortunately, so there's no fixing it with a lightweight.

I've heard something odd once from BMW guys mixing MTF with ATF but I highly recommend against that just based on lack of information.

I have a noise coming from my flywheel at 2600rpm almost exactly. It does it in neutral, with and without the clutch pressed, during acceleration and deceleration. Do any of you gentlemen have an idea of what it could be? This is about the closest thread on the issue I'm having. Also don't know what weight flywheel I'm running because I bought the car used and have not yet looked into it.

Check your thread start for my update ..... TOB (Throw Out Bearing) ...... seems we are having an epidemic here ..... :sigh:


humfrz

Does it only happen when decelerating in gear? Or in neutral to? Here's a vid of mine after I installed my exedy clutch https://youtu.be/J2lUuzmd2fc

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