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Opinions/experience on twin disc clutch vs carbon single

 
Old Apr 14, 2019, 12:19 PM
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Opinions/experience on twin disc clutch vs carbon single

I'm trying to decide between getting a conventional metal twin disc vs a carbon single and would appreciate any input. I've never owned a twin disc myself but have driven cars with them. I've owned the carbonetics problade single clutch, and I still think its the best clutch I've ever had. This includes stock, ACT HDSS, and comp stage 2. My use is 50% street driving (just for fun) and 50% road course / time attack use. Fast, high RPM shifts and not harming my trans are the big priorities over launching. I'll basically never launch my car and have no drag racing intentions. Just not my thing.

My only hesitation is over the power level I'm going to. I'm expecting at most to see something like 500-550lb/ft torque with my 2.2 stroker + EFR8374 combo on e85. This is on a 3200lbs car and with a 4.11 FD gear. The torque is far outside what ATS (they own carbonetics now) recommend for their carbon single, but Curt Brown did have a lot of success running it even while making tons of power on fpgreen to fpblack.
https://www.evolutionm.net/forums/ev...een-dbb-2.html

I've actually seen his clutch after he got through with it and it still had more than 80% of the material left despite him running 10s with the FPblack on it. But I think he had stock FD gear and his car was notoriously light. ~2800lbs.

Anybody else have any experiences to share? I'd like to go with the ATS single carbon again but even ATS recommended their twin metal system because it is more "durable" and cheaper actually. I just dislike the twin because I will never launch with it, they can warp easier than a carbon single, and it eventually makes a ton of noise.
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Old Apr 14, 2019, 12:57 PM
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I think going against manufacturer recommendation, especially when you aren't forced to do so, is a bad idea.
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Old Apr 14, 2019, 05:57 PM
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Why not go with "the best clutch I've ever had"?
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Old Apr 14, 2019, 08:22 PM
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Originally Posted by barneyb View Post
Why not go with "the best clutch I've ever had"?
Not rated at a high enough torque.
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Old Apr 15, 2019, 09:49 AM
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Originally Posted by kaj View Post
Not rated at a high enough torque.
If he was going to the track or drag strip I'd agree with you.
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Old Apr 15, 2019, 10:11 AM
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I would expect a 2.2/8374 to make more in the 600wtq range unless you're planning to not push it hard.

If the "goal" is to stop in the 500-550 range, the exedy twin is the ticket. It shifts well and has really good street manners.

I would also be hesitant to exceed the rated capacity of the clutch. The sprung hub is also a factor in torque rating, not just how much the friction material will hold.
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Old Apr 15, 2019, 10:31 AM
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I had to replace a nearly new Exedy disc when the sprung hub springs collapsed and all I do is mild driving. So, even from the makers with the best reputations you sometimes get junk. So, I rather pull the transmission again than go with an expensive clutch that might be junk.
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Old Apr 15, 2019, 01:16 PM
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Originally Posted by barneyb View Post
If he was going to the track or drag strip I'd agree with you.
I'm just going by what OP says. Either way, I wouldn't want to push a clutch past it's rated capacity. That's just me, though. On a side note, those carbon clutches are awesome. I'd love to put one in my car, but they are out of my budget
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Old Apr 15, 2019, 02:24 PM
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I'm going to stop at 35psi or 550wtq with reasonable timing, whichever comes first. My setup needs to survive road course use so I don't need any hail Mary numbers.

Yea I've heard and watched people I know have problems with clutch drag, noisy AF cars, and short life spans with twins. I'll never launch car btw so half the advantage of using a good twin I'll never use.

The carbon single is expensive but so is going through a twin very often. At 310whp the carbonetics problade I had was extremely durable (aside from launches). I know the clutch is only rated to 300wtq but CB did put down 610wtq with it and never had issues with it slipping. I'm considering ignoring the manufacturer's rating only because I think they're underrating it. Just like the 4g63 is rated for 276hp lol. But wondering if anyone had negative experiences at high HP with the carbon single.
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Old Apr 15, 2019, 02:43 PM
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Probably not because everyone that runs that much torque upgrades to appropriate clutches.

As for road course work... that thing is gonna be a handful. You'll be making more power and torque than you could ever use. Sounds like a lot of fun, lap times be damned I'm the same way: lap times are great and all, but having fun always comes first.
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Old Apr 16, 2019, 12:29 AM
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Originally Posted by kaj View Post
Probably not because everyone that runs that much torque upgrades to appropriate clutches.

As for road course work... that thing is gonna be a handful. You'll be making more power and torque than you could ever use. Sounds like a lot of fun, lap times be damned I'm the same way: lap times are great and all, but having fun always comes first.
You're really against this clutch! Not everyone is well acquainted with carbon vs metal clutches so I'll explain the reason why this is even a question to me. I'm not an expert on clutches but I do read research articles into these kinds of questions.

Carbon clutch characteristics differ from metal in that they have a much higher heat tolerance, but also have a very low wear rate and have a much higher "burst strength" (the static friction coefficient is much higher than the kinetic friction coefficient) compared to metal. That's why they suck at smoothly engage if what you want to do is ride the clutch, and are very chattery. They're more on/off switches.

The latter also means they suck at drag launches. Not because the carbon fails, but the metal parts actually overheat and warp/fail. For the ATS clutch I have in mind, that would be the metal flywheel and pp (how my carbonetics problade failed). So for drag racers or anyone that want to do good launches...single carbon is not the ticket. Twin and triple carbons can give you more modulation, but definitely a single is too on/off*. That 300wtq I strongly suspect is accounting for the stress of drag launches, which is what many other clutch manufacturers rate for. If a metal clutch can handle 300wtq at launch, it can usually handle way more when the car is already in motion. This should be even more true for carbon clutches since their static friction capabilities (when the clutch is not slipping/engaging) is so much higher. So the ATS rep might tell me no more than 300wtq, but that's what the problade was also rated for and many people put down 400+ wtq through it. CB put 600+ wtq through it on a dyno at least. And it never slipped for him. It was still holding probably because it IS carbon rather than organic/cerametallic/etc. In fact, even though ATS doesn't want anyone launching with the carbon single, they still have launch instructions for if you do (don't slip for more than 0.5s). Indicating it should hold 300wtq at launch if their torque rating standards are comparable to other companies.

Why am I so hung up about the single carbon? Because it has an extremely light MOI and shifts amazing. I haven't felt anything shift better yet (exedy twins included) and that was with the inferior problade design that was heavier with a sprung hub. The new ats clutch is unsprung and even lighter http://www.ppi-ats.com/images/Single_C_Clutch.jpg. Even if you botch a heel-toe downshift it doesn't matter cause the thing is so light it will just rev match for you! The clutch MOI is even more important with the huge rpm drops with a 4.11 FD.

If I was making 400wtq, I wouldn't even hesitate. But I'm going for potentially higher (I'm not targeting numbers, it makes what it makes) and so was wondering if anyone had experience. Because I have a n=1 in CB right now with an older style clutch from a company ATS bought out 5 years ago. And his car weighed 2900lbs with stock FD gear whereas mine weighs 3200lbs with 4.11 FD.

I don't have a huge social presence on evom, but that doesn't mean I'm not a track rat . I probably have much more track experience (and my car has much more track miles) than you're expecting. Or at least it used to be in years past. I just don't have enough seat time to be competitive anymore and ever since the DBA-R35 came out I had no chance of winning in awd classes. The ct9a is an old chassis that is outclassed unless you really get intense with it. So no I don't care about lap times as long as it's faster than my buddies. And that really comes down to the driver than the car. Regardless, my chassis is pretty well setup and can easily handle way more than the 310whp I was pushing around with my stock turbo. In fact I killed my stock motor pulling a sustained 1+ g right sweeper on street tires. I didn't have a dry sump or a modded oil pan.

Last note, I'm not really worried if the clutch slips. If that starts to be an issue I can a) turn down the torque, b) swap clutches. But both are better than going for a super aggressive drag clutch that would destroy the drivetrain. I've already broken the trans, tcase, and rear diff on separate occasions (all at the track like a true gladiator) and have learned the importance of having the clutch as the weakest link. As TRE says, the clutch is supposed to be like a fuse.


*Side note: ATS makes a full carbon single plate clutch (i.e. carbon/carbon and carbon hub) which is rated to 800hp and they have no problems with you drag launching it. This is because it has no metal in it to warp and fail under heat. They don't make a full carbon single for evos though, and it's also $5k...

Last edited by deeman101; Apr 16, 2019 at 10:41 AM.
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Old Apr 16, 2019, 12:33 AM
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Doesn't look like many people have the experience I'm looking for to address this question. I think I'll just bite the bullet and try it out. If it doesn't work out I'll detune until it holds and replace with a twin when I get a chance. Will post how this goes!
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Old Apr 16, 2019, 08:16 AM
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Curious to know what company carbon clutch you will go with? I don't think I will use that for myself but I don't mind to research.

Thanks,
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Old Apr 16, 2019, 09:33 AM
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You are looking to greatly exceed a clutches recommended capacity. We're saying we wouldn't. That's not being against anything. I love the carbon clutches.
If you decide to go for it, I say more power to you (pun intended).
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Old Apr 16, 2019, 10:53 AM
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My exedy twin had over have the thickness left on the disks at 20k miles. I'd say that's pretty good. And its only noise when the clutch is disengaged, and I don't sit at lights with the car in gear and the clutch disengaged so it never bothered me.
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