s-cam

Just wondering who has put twin Disc clutches in and how they liked them or if they would recommend them. I am looking to put one in my V1 to replace my monster stage 3 clutch. I need a clutch to hold 850-900HP and yet not chatter at the stop lights. car is 95% weekend driver, and hopefully 5% track use. Any recomendations on a clutch or companies to buy one from ??? I have only looked at ls9x twin disc and mcleod's but i figured i would ask for some real world feedback before i take the plunge.

Onefast V

iTrader: (3)

exedy twin. Few people have them but i've heard nothing but positive from them
http://store.katechengines.com/exedy...-gto-p238.aspx

philistine

iTrader: (2)

The Katech LS9x or LS9R is more for street applications that can handle some mild track duty. Your HP goals are at the limit of the stock transmission and LS9x/R.

I can comment on only that clutch but with stock power. It's very comfortable and a pleasure to drive DD. It has smooth engagement just like OEM but much more grab. These do not chatter. There is also no issues with the idle with the extremely light 12 lb flywheel.

FuzzyLog1c

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S-Cam! Long time no see! How's the V doing?

Philistine has very high standards, and I respect his opinion and experience. Unless you've increased the amount of boost that you're developing since the last time we talked, the LS9x might work, but I worry that you may break its pressure plate straps. Brian (PISNUOFF on CF) might be a good person to talk to about that.

Another option is the Mantic 9000 series, but if you have the money for that, you don't need to listen to us babble. The McLeod RST and RXT are solid options, but I cannot personally speak to the RST's driving characteristics. I believe it will be very similar to the LS9x, but with about 25% less inertia. The other thing is that, like the LS9x, the RST has organic, sprung friction discs that will grab more gently than your Monster Stage 3 and my RXT. However, sprung discs can create problems shifting at very high RPM and their springs are the most frequent cause of catastrophic clutch failure on high horsepower machines.

s-cam

the V is doing pretty good. Running approx 19lbs boost now and thats probably where it will stay without a supercharger overhaul ( or change over to twin turbos but I think i will use a different chassis when the time comes)

I swapped gears in the rear from 4:10 to 3:42 and am not happy with the clutch chatter. It would be fine for the track but when you are driving in town with the wife the chatter is annoying. I have to say good things about the monster stage 3 and how it holds close to 800 RWHP but the drivability is not great, or not great for me anyways. I am taking the trans out to do some work to it and figured its a good time to swap clutches.

I was really interested in an RXT . does it chatter much or is it pretty good? I was trying to figure out if I could use my monster flywheel and buy just the clutch? if anyone knows that answer it would probably sway my decision as I dont know if i am prepared to drop over $2k on an Exedy clutch....

runsfromdacops

i sorry to say but if you want 900rwhp and no chatter your high.

i have both 900 and the chatter that comes with it.

the rxt isnt that bad but if you dont slip it just right it will chatter.

DMM

RXT's seem to be hit or miss. Got mine in the same group buy as Fuzzy and had nothing but problems since day one. It chatters so bad it feels like it'll break the glass in the car. Have spoken to tech assistance twice now and have basically been told to F-off. I have pics posted in a recent thread, you can see for yourself.

I have hopes to get something more definitive from McLeod other than "it's supposed to be that way, but we can rebuild into ur brand new RXT for $540 if it doesn't get better" after the New Year. Not much I can do from here in NDjamena, Chad.

FuzzyLog1c

iTrader: (4)

I'd like to take what runsfromdacops said and invert it: "if you slip it just wrong, it will chatter."

That's an important distinction to make, because it implies that anyone that isn't determined to drive their car the exact same way they drove it prior to installing the clutch can circumvent chatter. If you have bad habits, a ceramic clutch will let you know. With ceramic clutches, you can't generally correct for poor technique by adding throttle--they're just too grippy.

Because the McLeod RXT uses ceramic friction discs, it grabs like a bitch. It will chatter if you try to slowly release it, or try to force it to slip by flooring the gas (at least on my small LS2--a larger, supercharged engine might be different). To start the car smoothly every time, set an engine RPM, confidently release the clutch, and as your foot traverses the last 25% of the clutch pedal arc, add a little throttle.

FuzzyLog1c

iTrader: (4)

Geeky discussion: given a fixed set of inputs from the driver, the occurrence of clutch chatter depends on the following things:

• The static and dynamic coefficient of friction of the clutch and flywheel material--which are affected by temperature and ambient relative humidity.
• Drivetrain resonance frequency (2-6 Hz in consumer-grade vehicles, and 6-8 Hz in performance vehicles) versus flywheel RPM during clutch engagement.

The first bullet point suggests that clutch chatter may occur once, and then not a second or third time because the act of slipping the clutch increases its temperature. Generally speaking, most people (myself included) find that ceramic clutches chatter most when cold. So that first time you pull out of the garage, you might experience chatter--if you were right on the edge of the conditions necessary for it to occur. At the next light, if you start the car the same exact way, it might not happen.

The second bullet point suggests that the presence and severity of clutch chatter is application dependent. Unfortunately, the first generation CTS-V drivetrain is long, and worse, pliable. Even with all of the 95A Revshift bushings installed, my stock drivetrain and 4th generation Getrag differential clunk from torque reversal when I disengage the clutch, abruptly let off the throttle, or hit the gas.

Rubber motor mounts + short transmission [tailshaft] + rubber coupler + long driveshaft with undersized carrier bearing + poorly-reinforced differential = recipe for drivetrain torque oscillations. I expect the window of conditions necessary for clutch chatter to occur to narrow when I install my Geforce 9" IRS over Christmas break.

427zm

iTrader: (9)

http://store.katechengines.com/ls9x-...ts-v-p247.aspx

FTW. Many Vette guys use this frequently on 600+ HP builds. Stock pedal feel and drivability. In my dad's C6Z he gained 12 wheel just from adding the clutch. The lower weight translates directly to the tires.

07CTS-V

iTrader: (6)

I stopped reading 1/2 way through the above comments.

It took me about 3 months total to break the pressure plate straps on two LS9's and I went on to an RPS (turboclutch.com). I broke the Marcel spring in my first one after 1.5 years, I was talked into getting the 'street twin' which was 1/2 organic, 1/2 carbon and had a Marcel spring to eliminate the chatter. It didn't chatter at all and after a year and a half of abuse I dropped the trans while pulling the motor and noticed the Marcel spring was broken. I upgraded to the full carbon without a Marcel spring. It chatters if you don't drive it properly but works well and hasn't broken yet (only been three months).

I have the LS9 flywheel if anyone is interested. It's a little scratched up but works fine without any vibration.

Brian

FuzzyLog1c

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You may have gained 12 RWHP from a newer tune, better conditions, or statistical variances, but you did not gain additional power output from the clutch. Put another way, the clutch doesn't factor into the steady-state losses generated by your drivetrain. Dynamic conditions, on the other hand, are a totally different story.

DMM

My experience has been the exact opposite. My RXT chatters when cold and gets much worse as it gets hot, to the point of where it is not drivable. It feels as if the friction pics are trying to skip off the flywheel and floater like rocks skipping across a pond, and they have the metal/metal wear on the surfaces as a result.

427zm

iTrader: (9)

Of course it does. Less rotational mass equates to more power. It's a more efficient setup. What's drivetrain loss? It's the loss of power from the flywheel to the wheels. The clutch is in the drivetrain, just as wheels, tires, and driveshaft are. Added weight in the diff, tires, wheels, clutch, or driveshaft will mean a loss of power to the wheels, just as less power rain weight will equate to more power.

427zm

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He went from an LS7 clutch to the LS9X, and lost 30lbs in clutch alone.

FuzzyLog1c

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All of the things that you just described are sources of inertia, and are not measured by a dyno.

427zm

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On a dyno jet, they will definitely show up. Even on a Mustang,it'd show. Dyno jets work by how quick you can spin the drum, and these weight losses will increase inertia and spin the drum quicker. Just as on the street, you would feel the tires spin easier with a lightened flywheel/clutch setup.

DMM

S-cam....Chris at SNL hit me up about their new C7 based twin. Maybe you can ask him more about it.

427zm

iTrader: (9)

Yes, that C7 setup looks pretty cool. And while you're at it, ask him how a lighter clutch and flywheel equates to more dyno power and faster track times. SNL did the work on my dad's car, and mine. And Chris will, definitely tell you that a lighter clutch setup will give you more wheel HP due to less power train loss.

FuzzyLog1c

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