byebyeL98

I am using a Valeo sprung clutch disc. I was told it would reduce noise a bit and have slightly smoother/easier engagement qualities than the unsprung disc. I can't comment on the differences in "feel" or noise between sprung or unsprung (since I don't have any experience with unsprung), but the total set up does not feel all that different from the Centerforce II set up I had with the old 4+3.

95PoloVert

I have a buddy who does quite a few HDPE/road-race events in a geared Z06. He loves it for that purpose and claims the difference is very noticeable.

Since reducing drivetrain mass increases the rate of acceleration, the difference is most noticeable in lower gears and in conjunction with lower (higher numerically) rear-end gearing.

tjwong

In a customers 96 C4 with a McCleod SM and street twin setup, the noise is very noticable at idle with the clutch out in neutral. This car has a nasty roller cam in it that has a fairly rough idle which will aggravate the noise. On a stock car or one with a much milder cam, the noise will be much less noticable. I have driven a ZR1 with the same clutch setup but with much less cam, and at idle it was nearly as quiet as a stock ZR1. Bottom line is, if you have a lumpy idle, its going to aggravate the noise, the smoother the engine idles the less noise you will hear.

jsaunde2

I have an iron single mass flywheel with a sprung disk and I wouldn't do it again. It isn't so loud it would give you a headache, but it is loud enoguh that people will wonder why your driving a car with such an obvious problem. It also gets louder as the transmission lubricant heats up and thins out. It is a relatively low frequency metallic clanking/rattling noise at idle and becomes the dominate sound of the car on a car with cats and no mufflers outdoors; so it's pretty loud.

There is also the issue of gear rattle under load in certain conditions as mentioned before. Basically, I wouldn't do it unless it is primarily a track dog or you just can't spend the money.

Jason

rocco16

Shouldn't.
If the clutch was engaged, then the sprung hub would be inactive.
If the clutch is disengaged, then there would be no power pulses (which is what sets up the gear-rattle) going into the gearbox.

Sprung hub only comes into play during that brief moment of engagement, which is not when gear rattle is noticed.

That's how I look at it anyway....

Larry
code5coupe

CentralCoaster

I think the sprung hub is intended to dampen the vibrations on most applications (since when is a spring a damper anyways?), but reading up on the ZF6, the springs didn't do anything for the gear rattle, so they were not used. I don't remember the source.

jsaunde2

The theory I've heard is that the vibration in a C4 that would normally be damped by a sprung disk is damped by the dual mass flywheel so the sprung hub was unnecessary.

I believe the sprung disk should dampen vibration when the clutch is engaged but not under load.

Jason

rklessdriver

My Spec Stage3 has a sprung hub. I drive it almost every day in DC traffic. IMO its pretty easy to drive with the alum FW once you get use to it.
Different people have different tollerance levels for this kind of stuff. You'll have to find someone with one in their car and see for yourself.
As for the acceleration difference... It was a good running car before but once I changed to the alum FW its like a totally different car. Launching it on regular street tires or Drag Radials is way easier to manage now, before it was either bog bog bog or spin all the way thru 2nd gear. I really like it and have no plans to ever put a DM FW back in my Corvette.
Will

TPI

Thanks for all of the feedback guys. I'm leaning toward going aluminum SM since I have the blue tag trans, but still undecided. It's not cost. I want the most performance I can get, and still be streetable. A sound bite of a blue tag trans might help. A real live example would be better. My motor is on its way. the cam is 224/230 @ 0.50, and 536/534 recomended by comp cams. they say it will pass smog. I don"t know how it will idle. I think not too lopy. More input apreciated. I have a week or so to decide. Thanks

Red Tornado

I'll second that. I HAD a Fidanza aluminium 13.5 pounder, and I HATED it. I also have a somewhat lopey idle (due to modifications), and with my black tag '90 ZF, the FW combo raised hell. It was like listening to a tin can with big rocks, violently shaken by Goliath. It was mainly at idle, and I constantly had to engage the clutch to relieve myself of the insult. And I got tired of hearing it, and I got tired of hearing comments from strangers. So I had it ripped out and went back to a new Luk DM unit. Very happy ever since. Noise was only part of the reason I hated it too.

Red Tornado

Probably will have a lope to it, a bit more than mine anyway. My cam is only a 219/219 (LPE/Accel). Have the idle RPMs increased to about 850-900 re-programmed on your chip, this will bleed some of it out.

SM performance? I didn't notice anything added really. I disliked the gas pedal racer rocket-gun approach to the initial launch required, from a dead stop. Thats cute for the track, but it gets old on the street. Just MHO. I will say this -- you will attain the upper rev range quicker, no doubt about it. This aspect is probably one of the biggest pros going for an ultra-light SM. For me, that was a big whup.......I get plenty fast there -- and I mean in a hurry, even with my DM flywheel.....then again I've got the whole mods treatment.

In the final analysis, maybe some black tag ZF's are inherently noisier than others......same goes for blue tags......maybe its the specific engine build combo and from car to car.......every outcome is probably a little different.......you won't know until its done.......and the just maybe I'm too sensitive and don't appreciate all kinds of noises other than the whallop that's bellowed out my cat-back......everyone is different

95PoloVert

How exactly do you rev quicker in gear without a performance gain?

Red Tornado

I suppose you could call that performance, technically of course it is a characteristic that's improved......but I get that anyway even with my stock DM since I've got a good deal more power than stock L98. I apologize for any confusion, as I'm typing with my own singular perspective

95PoloVert

Hi Brad...haven't talked to ya for a while. In fact, I think it was last Spring when you were selling your Fidanza. (...and dealing with that sticky "tuning issue". )

What I was referring to is that revving in gear is acceleration, right? Since your drivetrain has less inertia, power that would be absorbed by the 25 extra pounds of your DM goes instead to the tires. Unless you're traction-limited, that translates to greater acceleration, doesn't it?

From the conversations I've had with Fidanza users in the past year or so, there seems to be 2 key ingredients to a happy user: Idle quality (noise reduction) and lower gearing (driveability and additional performance gain).

I have a Fidanza in the garage awaiting the next weekend that I can play in the garage...so I'm interested in everyone's perspective. When you said you revved quicker in gear but didn't see a gain, I just wondered what I was missing!

-Scott

Red Tornado

Hey Scott! It didn't dawn on me that was you You're exactly right. I suppose that I've let the negative aspects (in my case) get the best of me by letting them overshadow the fact that yes, revving quicker gets you some added gains. What I found out was that I get there about as fast when I went back to a stock DM.....but this wouldn't apply to someone with a stock L98 engine (as I rememeber it revved somewhat slower without the engine mods).....so since I'm really an apples and oranges comparison, some of what I said wouldn't apply to someone who is mainly changing out their DM setup with a SM and leaving everything else pretty much stock

Yeah that "tuning" issue (and I must emphasize its not the tuner in my profile, for anyone not in the know).......thank God its well over with, all paid off, and in a land far far away now................

Great to hear from ya Scott!

95PoloVert

Glad it got handled...sorry if I dug up any bad memories. I should think before I type... I'll have to buy you a beer next time I get out your way!

-Scott

Red Tornado

NP Scott, its all good......Please contact me before you come, would really enjoy that.....we'll meet up at the local Hooter's or something

LD85

I had an unsprung disc with my Billet Single Mas, waaay to much chatter for me when the disc would engage. I took it out with no more than 200 miles on it, and put a sprung disc in. Much much better.

I have it haning on the wall in th garage, I will let it go reaaal cheap!

As far as noise, you have to realize, these tranny's make noise, it is just a fact, mostly in neutral at idle,,,,as already stated.

TPI

What was the other part of your reason for not liking the aluminum fly wheel?

TPI

It sounds like the clutch used with a Fidanza aiuminum FW might make a difference. Who has had a good result with an aluminum FW, and what clutch was used, and vica versa?