Got a JWT flywheel, clutch plate, clutch disk, pilot bearing and stainless clutch line combo installed last week. I also did the concentric slave cylinder / release bearing and concentric slave cylinder tube while I was at it. This isn't a cheap upgrade - parts are almost 1K and then you've either got to install it yourself or kill the better most of a weekend doing it yourself.

Pros:
1. Flywheel and clutch disk were balanced, so all the vibration you are used to in the clutch pedal and shifter are gone. Confirms my suspicion that the stock Infinity flywheels are not balanced well.
2. Engine revs significantly faster, car is significantly more responsive, particularly in first gear.
3. Weird hesitation that occasionally happened when you hit the gas does not happen now.
4. Clutch engagement is much smoother.
5. 1st gear take off easier to do smoothly.
6. Rev. matching on downshifts much easier.

Cons:
1. A LOT of noise and vibration comes from the transmission if you load up the drive train under 2K RPM. In other words, if you are used to upshifting early to save gas, forget about it. My belief is the stock dual-mass flywheel masked this vibration by smoothing out the engine pulses. I'm really surprised how bad the vibration is with the new set up. Sounds like an old school bus going up a steep hill (lots of gear whine). Once you get past 2K RPM, it goes away. I've done light-weight flywheels on other 6 cylinder cars, and have not had this problem.
2. Clutch pedal is very stiff. You'll get very tired of using the clutch in stop and go traffic. I had put a lighter-weight spring in the clutch pedal mechanism with the stock clutch, but switched back to the stock stiff spring once the JWT clutch plate was installed. This helped, but the pedal is still very stiff. If I had to do it again, I'd stick with a new stock clutch plate and keep the lighter spring because this makes it easier to feel the beginning of the friction zone.
3. Some release bearing noise, particularly when the car is hot. Seems to be getting a little better each day. CSC is self-adusting, so perhaps this is taking up the clearance between the release bearing and the clutch fingers and reducing the chatter.

If I had more time and money than I do, I think the hot tip would be to machine mass out of the stock flywheel, get it down to 12 to 14 pounds or so, keep the dual mass set-up, get a new stock clutch plate, and balance the clutch plate and flywheel as a set. You'd have to be very careful how you did this (to avoid the hole thing from flying apart at 8,000 RPM) but I bet you'd get the best of both worlds. The problem is that the rotational compliance the dual-mass flywheel gives you to reduce the driveline pulsation at low RPM is the same rotational compliance that makes taking off in 1st gear smoothly very difficult with the stock clutch.

I'm curious if other JWT uses have had the same experience......

 

From everything I have ever heard/read, you're impressions are pretty much spot on; As nice as the responsiveness gains are, civility is hard to come by without that (stock) dual mass fly. I'd love to see a modified dual mass setup as an option. If someone could pull that off, it sounds like the best of both worlds. I'm not holding my breath though; if it was even remotely feasible, I'm sure someone would have offered it up by now.

 

I installed the same combo two days ago and echo both the pros and cons as you've listed except for maybe the stiff clutch pedal. Finding this post helped my comfort level with my experience. Everything seems to be fine.

 

I'm starting to get the whine noise at idle below 1k rpm but if I give it gas it goes away. Everything you stated is spot on!

 

Im ordering one in a few weeks and GLAD you made this review. So all in all, would any of you that already have it "do it all over again"? Is the performance gain worth all the cons? This is my daily btw. Your answers will be much appreciated

 

Why not get an exedy clutch?

 

So pretty much the pros are increased performance and the cons are just noise? I can live with that cuz mine already sounds like a concrete mixer except it slips in every gear over 4k.

 

Well, I hear you saying that, but if you've still got a dual-mass flywheel on there, then the sound you're already hearing should still be significantly better than how any non dual-mass fly would sound.

 

while the car would rev quicker with the light flywheel making you 'feel' like the car is quicker, you wont actually gain any noticeable HP, iv seen a few non-biased dynos and the gains were 0-2whp on average with some questionable gains as well around 10whp. The light flywheel does make downshift rev matching easier and a bit more fun but the sound and clutch feel is not worth it imo.

 

I have the same clutch flywheel combo, I posted regarding my stock csc in another thread, basically, the stock csc failed within a couple weeks due to the high pedal pressure/hydraulic pressure required to push the heavy pressure plate springs. Solved heavy pedal feel and reliability with zspeed HD csc. I highly recommend this piece if your going to put a heavily sprung pressure plate on, regardless of brand. the stock csc cant take the pressures involved. Good luck to all, y'all

If i was doing it again, i'd probly get a lightened flywheel and use a stock clutch, unless your going boosted to big hp.

 

I agree, if I had to do it over again, I'd probably go with the stock pressure plate and the light flywheel. I have a new, but stock CSC and so far no problems (been about 4 months). If it fails, I'll either do the Zspeed or just go back to a stock pressure plate and keep the light flywheel.

A few other comments -

Everyone always says the light flywheels are noisy or "chatter" and although I now have had the same experience, it never made sense to me. I'm 99% sure the following it what is actually going on:

<> It's not the flywheel itself making the noise - it's the fingers of the pressure plate which are acting like half-tuning forks.

<> When the clutch pedal isn't pressed in, the CSC is not touching the end of the fingers and they are free to vibrate.

<> With a relatively heavy flywheel, even at low RPM (say 700 RPM = 11.7 RPS = 35 engine fires / sec = 29 ms between fires) the engine isn't changing speed much between fires. The heavier the flywheel, the less speed variation.

<> A heavy dual-mass flywheel is even better, as it can be tuned via. spring rate and mass choice to have no speed variation on the clutch-side of the flywheel at a particular engine speed and load. Think of it as each cylinder fire compressing the springs, which slowly (relatively) release energy and ideally completely unload just as the next engine fire comes along. The engine-side of the flywheel has a changing speed, varying 3 times a revolution in the case of a V6, but the clutch-side of the flywheel is spinning at a constant rate.

<> Since the clutch-side of the flywheel is spinning nice and smooth, there is no energy present to vibrate the clutch plate fingers.

<> Switch to a light-weight flywheel, and all of this changes. The clutch side of the flywheel is now varying in speed, and this energy can go into vibrating the pressure plate fingers which can make a racket.

<> If you do something to increase the load on the engine at idle, like say turn on the AC, the speed will vary even more, and the noise will get worse.

<> Step on the clutch pedal and the CSC moves out towards the pressure plate fingers, contacting them and stopping them from vibrating, and the noise stops.

<> If you kick up the idle a bit, and get more fires/sec, you'll get less speed variation, and less noise.

<> I think the V6 configuration also makes this worse than it would be for a straight six. V6's are inherently unbalanced. If this sounds crazy there is a nice non-technical write up at http://en.wikipedia.org/wiki/.
For a really, really technical analysis you can read the last chapter of Shigley's Mechanical Engineering Design, but this get's very deep very fast.

<> The inherent V6 imbalance is not rotational, but end to end rocking, but even so this can't help the situation. I've put light flywheels in straight sixes, and had chatter, but never to the extent this car does. I'm guessing it's the V6 vs. I6 balance.

I've been really tempted to design a chatter damper for this problem, and even have a design I think would work, but who has time to rip out the transmission every time you want to test a design variation? I also think the strange-looking secondary springs in the stock pressure plate that are not present in the JWT design are just this - springs whos sole purpose is to try to damp out the noise.

I'd love to know if someone trys stock pressure plate + JWT flywheel if the chatter is better.

 

Almost forgot, as far as the HP question goes.....

You will hardly see any improvement on a dyno with the light-weight flywheel, mostly because the dyno runs are done in the 1:1 gear (typically 5th with a 6 speed) and here the flywheel won't make any difference.

Here's the deal:

In first gear, when you have a heavy flywheel, a significant amount of the energy coming out of the engine goes into just spinning up the flywheel.

I did a simulation of this once at http://my.is/forums/f93/clutch-advic...4/#post4692130

for an IS300, which mass-wise, trans-wise and flywheel-wise isn't too different from the G35 sedan.

The short story was, with the stock flywheel:
<> 28% of the energy of the engine goes into the flywheel in 1st gear.
<> 12% in 2nd gear.

With the lighter flywheel:
<> 18% in 1st gear.
<> 7% in 2nd gear.

The difference keeps going down as you go up in gear. The reason for this is something called reflected inertia, and it basically means the engine "sees" the mass of the flywheel directly, but sees the mass of the car reflected through one over the square of the combined gear ratio of the transmission and differential. So, in high gears the car looks heavier to the engine than in low, and the car mass completely dominates the mass of the flywheel (flywheel mass might only be a few percent of the total). Lighter flywheel doesn't change what the engine sees (much). In low gears, however, the car mass and flywheel mass are closer (from the engines point of view) so the lighter flywheel makes a difference in the total (flywheel mass can be as high as 30% of the total).

 

I think this might be the next thing i get. the stock clutch on the sport is alright but def need a little somthin better. good stuff johnpawlak!!!

 

I find that when I change gears at near redline, the clutch will slip on my sport. feels like it needs higher clamping force.

 

CSC? Is this the slave cylinder?