Got the JWT 14lb flywheel installed then put about 40 miles on the ride. First thing I noticed was how much easier the clutch peddle operated. The reason for this could simply be from the freshly lubricated linkages – I don’t know. There is a definite improvement in rev-response time. What didn’t change as I had hoped was the notchy entry into gates 2 and 3 (oh well, no loss there). Two things concerned me going into this mod 1) difficult launches, and 2) noise.

First off, I heard that people were having problems killing the engine because a higher rpm is required for a smooth launch. I found no problem with this simply because the engine revs up so much faster. The engine leaps to 3000 rpm so, if anything, my problem was over-revving. I also found my usual 4000 rpm shifts were happening at 5000 rpm (a little practice will take care of that). There are no hills here in south Florida, so I can’t say much about slippage except that it seemed adequate and doable without to much bitching from the trainy. One thing for sure is that it sucks when you are not first in line at the stoplight, because without even trying you are at cruising speed in about a 150 feet.

Now for the noise. This might be the one thing that kills my enthusiasm for this mod. The best way I can explain it is the trainy sounds like a somewhat subdued 2 ton delivery truck. To top that off, during acceleration I noticed a sound resonating through the cockpit that made zhit vibrate that never vibrated before. I’m one of those people that if I hear a rattle (in anyone’s car) I’m hunting for that damn thing so that I can kill it. But, as advertised, above 2200 rpm everything quiets down and the ride is comfortable. You have to keep in mind though that you go through that “uncomfortable rpm range” with every single shift. My mechanic, Mike Wade, said that after break-in he would change out the fluids to something with a little more viscosity and that will quite it down considerably (we’ll see).

As for my overall impression, the jury is still out. Its going to be a battle for me to see if the increased performance outweighs my need for creature comfort. Right now I would say for anyone building a fire-breathing dragon, “definitely go for it”, but for someone wanting to cruise the strip for chicks, “you might want to stay away from this mod.”

 

I too just had the JWT flywheel installed, along with their 1200kg clutch and a brand new engine (oil consumption). With their clutch, the pedal is a little stiffer, if you kept stock, that would be the difference.
Mine makes no unusual noises like have been reported by others, even when I lug it in 3rd gear.

 

Didn't get a new engine, but got a new transmission and a new stock clutch with my install. As far as the noise, it could be the different clutch, could also be the viscosity of the transmission fluid. My mechanic said for warranty purposes he would rather start with the recommended fluid. Then when we were sure of the new transmission go to a heavier viscosity. Your mechanic might have simply skipped this step.

I didn't say there was any "unusual noise" just "more noise".

 

Thank you for taking the time to post the review, another bookmark to my "part reviews" file has been added. Thanks again

 

What's the weight of the stock flywheel? 24 lbs?

 

i keep hearing about vibration problems consistently with ANY lightweight flywheel on the VQ35 motor.

i've used lightened flys before on other cars without ANY issues like someof you describe. slight increase in vibration is normal as the motor's vibration is no longer dampened by a heavier fly.


but it has me thinking... i know the flywheel had to have been balanced when designed and produced.

but does anyone know how nissan balances its cranks?


do they balance the crank pulley, flywheel, and crank individually then slap them together? or do they slap them together, then balance the whole unit by shaving the flywheel and/or crank pulley?


i know of motors that have been done with either technique...


but if the stock flywheel is not balanced individually, but balanced to the crank, replacing it with an individually balanced flywheel will result in vibration.



just a thought, as this problem occurs to everyone, despite different brands of flywheel. although some people may be a bit more melodramatic than others when describing the vibration and harshness.

 

Excellent questions above about the balancing. The answers can be the key to the flywheel and the UR pulley effects on engine longevity (harmonic balancing and torsional forces, etc.).

 

Stock Flywheel is 28lbs...

Stock clutch is about another 25/26 lbs (depending on 03/04 - 05

JWT Clutch = 24lbs
NISMO Clutch = 23lbs

 

Drift 350,

That is an excellent point. Got to put another 50 miles on her tonight. First thing I did was pull the Z out of the garage and let it idle while I stood outside and smoked a butt. Rattle! Rattling outside the car as well as inside. Turned of the AC (S. Florida) and the rattling stopped. Turned it back on and depressed the clutch and the rattling stopped. Not really a rattle more of a sandy rock-crinding sound that so many people describe.

Anyway on with my little trip... MAN is this thing fun. The car is so much more responsive. Takes absolutely no effort to get it to redline. Just driving normal I run out of gears in about 15 seconds. Call me crazy, but I also think the ride even sounds a little different. I know its weard but the Stillen true duals have alway been a little on the raspy side. But now the note seems to be an octave lower and maybe just a hair louder! Is it possible?

 

My experience was the same as your's. (I have the stock clutch and a JWT flywheel.) My performance and noise experience is just as you reported.

I get the same truck sound as you when giving the car gas at low rpm (lugging it), and I believe most JWT users (and most lightweight flywheel users on the Z) get the same. I usually shift at 3500 or 4000 rpm, though, so even after a shift the rpms don't really fall down into the "noisy zone." Even at low rpm, the noise isn't noticeable unless I give it gas. I also get the light rattle at idle, and it indeed goes away when you hold in the clutch. I believe all this is normal.

Changing your tranny fluid won't silence it. I changed mine after doing the install, and later I put in synthetic. No change. I don't know if different viscosities would change the noise, but I wouldn't risk it. I just stuck with factory recommended viscosities.

Overall I don't think the sound is nearly as intrusive as we're making it out to be. It only happens when giving the car gas at very low rpms (below 2k rpm), and that's pretty rare exept when starting from a stop. Even then, it's not so bad, and you get used to it pretty quickly.

 

Jreiter,

You're probably right. I paid a little more attention to the RPMs on my second drive and I did keep them just above 2k between shifts. That's on the high end of the uncomfortable range so its not so bad. Driving with the stereo on definitely drowns out the sound but not the vibration. I think the vibration is more from harmonics than from something out of balance. Kind of like that one odd time when an airplane flies over your house and something hanging on your wall vibrates.

But what Drift 350 said about the engine/flywheel being balance together could easily cause some people to have more noise and vibration than others. After sleeping on it, his statement has me worried. I'm getting hold of my mechanic first thing this morning to make sure he saves MY flywheel and I'll pick it up tonight.

Remember, I only have a 100 miles on this mod and my statements are my first impression. I'm sure after time I could get use to some of the noise. However, I will not hesitate to reinstall the old flywheel if I think the vibrations are harming the engine itself. Time will tell.

 

Put about 2k miles on the JWT Flywheel(with the JWT clutch) and I don't feel or hear the vibration you are experiencing.. I do hear the "sand shaking in a can" sound at low RPM's.. Recently installed the Vortech S/C and no unusual vib's. Perhaps the install may not of been done correctly?.Don't recall anyone mentioning a vib with this mod.

 

I get the rattle you guys are talking about at idle and i have the stock flywheel, but i plan on getting the jwt so i guess the noise wont be anything im not used to

 

with the tilton clutch, I get people making comments about my car all the time asking me:

"what did you do to your car? Did something break?"

or "what's wrong with your car?"

putting the car in neutral with the clutch out - after about 10 sec, it gets loud like there's a rock rolling around in a coffee can while being amplified by a mic

 

You don't experience just a little bit more vibration in your shifter with the lightened flywheel? I do. It's not a large amount by any means, but it's there. I expected this, though, since the stock flywheel is dual-mass and the JWT is single mass. Overall it doesn't annoy me since I know it's normal.

 

Uhhh my shifter vibrates with the stock clutch and flyweel

 

yeah the stock setup vibrates the shift **** a little during certain rpms

i haven't driven a jwt or nismo clutch setup, but with the tilton, it feels like the whole car vibrates if under 2500 rpm

 

just from personal experience, check the inner and outer of the flywheel, especially near the inner and outer edges... if it's been balanced to the crank, you'll find drilled out divots, where material was removed at pinpoint locations.

if it was shaved, it was probably balanced separately.


and to be positive, check the back of your stock crank pulley for drilling or irregularities... could be a balanced crank/pulley combo, but the lightened flywheel could be throwing off torsional balance.


the A/C think kinda worries me a tad more as the vibration stops when it's turned on like most people on here agree to... the ECU automatically compensates for the rpm drop when the pump is turned on, so it's not rpm idle per se. it may have a lot to do with simply the pump itself becoming a "vibration damper" on its own when activated... the vibrations are transferred to the pump, where the pumping of freon becomes a "damper" of sorts to reduce perceived vibration.


but being able to hear the car itself rattle from the OUTSIDE at idle makes me worry ALOT.


and as you guys well know, an unbalanced rotational assembly that rotates at those speeds saps power by way of resistance (like an unbalanced washing machine). this may be an explanation for why some guys are reporting a net LOSS of rwhp on the dyno (seen maybe 1 or two posts of guys who baselined and reran after install, to only be let down).


be safe there guys... i'd look into getting a scattershield at the minimum if you choose to keep the fly.

 

Is a scatter shield really needed at naturally aspirated power levels and such a low redline?

 

You are correct, but it vibrates a bit more with the JWT flywheel.