Lightweight flywheel without the noise?
 

For those of us considering forced induction a new clutch upgrade is just around the corner. A lightweight flywheel is an obvious upgrade while you are swapping out the clutch but my main concern regarding this is noise & chatter.

The few posts I have seen from ppl that did this already report lots of noise and chatter coming from the flywheel. Does anyone have any experience on this engine with a flywheel upgrade that is quite and refined? May be not be possible due to its design but worth asking...

Probably more attributable to the upgraded clutch than the lightened flywheel.

...NOT. The chatter with a lightweight single-mass flywheel is due to vibrations in the drivetrain, formerly dampened by the OEM dual-mass flywheel. I have not witnessed how bad the chatter is on the 370Z but we know it well from the 350Z. Usually this noise stops at anything over 2200-2400 rpm.

Porsche's dont do this. Well at least not my brothers 911.

My old 1990s MR2 turbo didn't do this either. Both don't have a long drive shaft or were built with less tolerances! ;) However, magazines have noted on the Porsche GT3 RS with it's factory lightweight flywheel that it chatters noticably!

hopefully some tuner out there develops a lightweight flywheel for the VHR that is not so light it doesnt absorb drivetrain NVH but is light enough to see some increased responsiveness and reduced weight.

I would think a lighter flywheel would reduce overall torque on the engine since you are reducing the the rotational mass.

What would be the benefit of a lighter flywheel?

Absolutely not true. It would reduce parasitic losses involved in the rotating the driveline (and in the other case a heavier flywheel). Ultimately it would actually improve tq and hp readings at the flywheel.

It will decrease inertia, which is not the same as torque.

^Yes you are correct, but who can make one that doesnt rattle and shake like an old VW beetle. That is the topic of the OP.

You can have your stock flywheel lightened as well if you want a less extreme set up.

Wouldn't a lightweight flywheel, make faster pick up and revs?

I have a Spec II upgraded Clutch and Flywheel and my chatter is down low between 1000-2000 rpm's. I don't notice it unless I am under geared. If you are in the right gear , you won't notice it at all.

The problem is changing from a dual mass to single mass flywheel. It doesn't really have to do with the weight of the flywheel, it's the design.

Like Xan said, if you want a lightened flywheel but do not want to have any additional noise, I would recommend having your factory flywheel lightened.

This is purely a personal feeling when it comes to noises and what not but I always relate clutch rattle or flywheel noise or anything like that to the character of the part and the vehicle. For example, if I were to ever purchase a Ducati, the very first thing I would do is get a drilled clutch cover so I can hear that dry clutch rattle. That noise is classic sportbike/ducati and I want to hear/celebrate it. Rattley clutches, clunky two piece full floating rotors, etc...In MY opinion...That is the soul of the car coming through. I enjoy/celebrate those sounds. I'm probably just weird like that though.

I hear yeah Kyle, there is nothing sweeter then the sound of cut gears to me.

Sorry, was trying to clear up a misconception...
Regarding the original question. It is actually gear rattle/lash that is taking place.
The noise is inside the tranny from the input shaft not being dampened by the dual mass flywheel. This makes sense when you think about when the noise is actually happening.
You are starting from a dual mass flywheel and going to a lighter single mass flywheel. Dual mass flywheels are used because of its properties with inertia - while harder to change the rotational speed - the benefit is that the power pulse transitions are smoother essentially cushioning the noises that would otherwise create gear rattle. Going to a lighter single mass flywheel you lose the vibration dampening benefits from the mass you lost.

The best way to mitigate this is by using a sprung hub which should help dampen pulses and changing to a heavier weight transmission oil. Dont think it is a question of what flywheel doesn't cause gear lash (the answer would be OEM), but if there is a combo that people have used that minimizes gear lash. I've used OS-G & Exedy combos in my car in the past, no issues - but it was on an FD (apples to oranges, since power delivery is different).