Yet another clutch question

[joshuaho96]

Transmission synchros feel pretty bad at this point in my car and sometimes the clutch feels like it has an inconsistent engagement point in the pedal travel. I figure if I'm going to swap in a new transmission I may as well also put in a new clutch. Obvious candidates are ATS's pull-type twin plate carbon clutch, Nismo Super Coppermix Twin, or some organic clutch option I haven't figured out yet. I have searched this stuff to death at this point and still don't feel all that confident in making a decision. Target power is not much. ~330 kW at the wheels max. I ballpark the torque spec at 600 N-m. The stock clutch feels a little light so a little heavier is ok but I would say no more than 15-20% additional pedal effort. For some reason most clutch manufacturers want to keep this stuff a secret but the Coppermix Twin is 950 kg clamp load so I figure it can't be too much heavier than stock. The hang-up I have is some people mentioning that the clutch is very grabby which sounds like a pain. The stock clutch is almost too easy to modulate so I don't mind if it requires more precision than that but I don't want to deal with something that feels like I'm getting rear-ended at every traffic light. Also I see some mention of the release bearing carrier sizing requiring some work which sounds like something that might complicate installation? It would be good to know exactly what is needed here for a 1995 R33 GTR.

The ATS clutch is supposedly the best but I've seen some complaints that they wear out easily and also slip when cold. I don't know how much of that is true but the cost is also huge compared to even the Nismo Coppermix twin plate. It's also unsprung which normally I would reject immediately but supposedly carbon clutches don't need it. The higher clamp load at 1300 kg is also a little concerning but to me more clamp load seems like it inevitably means more pedal effort and also more strain on the engine crank thrust bearings. 

This is a street car and despite being a weekend car I seem to spend a lot of time crawling in severe traffic congestion with it anyways so I will gladly pay to have something that is easy to drive on and will hold the power with no unexpected headaches. I really don't want to do a clutch twice.

[GTSBoy]

8HP conversion.

[Dose Pipe Sutututu]

1 hour ago, GTSBoy said:

8HP conversion.

Best option.

A cheaper option is a Xtreme Twin Plate, Organic Sprung Centre

[joshuaho96]

4 hours ago, GTSBoy said:

8HP conversion.

May as well buy an R35 at that point

[Dose Pipe Sutututu]

2 hours ago, joshuaho96 said:

May as well buy an R35 at that point

R35 shift times are woeful, garbage gearbox.

If you could ZF8HP that, then it would be better (probably nearly impossible)

[joshuaho96]

22 minutes ago, Dose Pipe Sutututu said:

R35 shift times are woeful, garbage gearbox.

If you could ZF8HP that, then it would be better (probably nearly impossible)

Getting back to the actual subject though the Xtreme twin plate I'm a little skeptical of. Higher clamp force + requires a pull to push clutch conversion. I'm not super sensitive to cost but the ATS clutch is 700 USD more and another 35% extra clamp force over the Nismo. With how weak the yen is the Xtreme organic twin plate is actually substantially more expensive than either the Nismo or ATS clutches as well, although I haven't priced everything out after shipping.

[Dose Pipe Sutututu]

17 minutes ago, joshuaho96 said:

Xtreme organic twin plate is actually substantially more expensive than either the Nismo or ATS clutches as well, although I haven't priced everything out after shipping.

Suppose in your part of the world, however here in Australia, the Xtreme Twin Plate Organic is still cheaper than any Nismo or ATS clutch.

[WMDC35]

Nismo is good but I've never driven something with Xtreme.

I'd been keen af to do an 8HP swap, sigh.

[Duncan]

I've got the nismo twin in the stagea, it is very progressive for a multiplate, medium pedal weight, holds the required torque no problems.

It is noisy with foot on the clutch but that may well be the gearbox bearings, it is ex race car 

[Dose Pipe Sutututu]

2 hours ago, WMDC35 said:

I'd been keen af to do an 8HP swap, sigh.

put the the house on DOGECOIN lol...

(no don't do that).

 

[WMDC35]

43 minutes ago, Dose Pipe Sutututu said:

put the the house on DOGECOIN lol...

(no don't do that).

 

15-20k for the 8hp would be a much smaller loss lol.

 

 

[soviet_merlin]

20 hours ago, joshuaho96 said:

The hang-up I have is some people mentioning that the clutch is very grabby which sounds like a pain. The stock clutch is almost too easy to modulate so I don't mind if it requires more precision than that but I don't want to deal with something that feels like I'm getting rear-ended at every traffic light.

Man, clutch feel is so subjective. I moved to the Nismo Twin from a heavy single plate NPC Heavy Duty Organic and it is sooo much better to drive in everyday traffic. A heavy clutch pedal is the worst here. The Nismo is light enough I don't even think about it. But with the heavy clutch in traffic I was aware of every time I had to push the pedal.

In terms of being grabby I would describe it like this:
- A normal clutch has ~10cm of clutch pedal travel between initial bite point and clutch fully gripping
- With the Nismo twin plate it's ~4cm of clutch pedal travel for the same

From what I understand that's normal for multi-plate clutches. Maybe the Nismo is more forgiving than others, don't know. It's not punishing but you have to get used to it. My driving is 80% city and no issues there. Smooth to take off and change gears. Hill starts are mostly fine. It is a bit of a pain for reversing on an incline. I find it hard to get the right amount of clutch slip for that and always end up feeling like I'm burning it too much.

But, you may have a very different experience based on your body type and footwear. With heavy boots or shoes it's likely going to be pretty shit. Just because the clutch is light and the boots don't give enough feel to let the clutch pedal out with precision. Might be similar if you are a big guy or have motor control issues. But able-bodied and driving with decent shoes it feels great.

You don't mention noise at all. It does chatter at idle RPM when it gets warm. Nothing that is out of place in a GTR though IMO.

[GTSBoy]

Maybe Josh could and should look at that UniClutch thingo too. The street twin one would take the power he's talking about easily. Light action and no noise.

[joshuaho96]

2 hours ago, soviet_merlin said:

Man, clutch feel is so subjective. I moved to the Nismo Twin from a heavy single plate NPC Heavy Duty Organic and it is sooo much better to drive in everyday traffic. A heavy clutch pedal is the worst here. The Nismo is light enough I don't even think about it. But with the heavy clutch in traffic I was aware of every time I had to push the pedal.

In terms of being grabby I would describe it like this:
- A normal clutch has ~10cm of clutch pedal travel between initial bite point and clutch fully gripping
- With the Nismo twin plate it's ~4cm of clutch pedal travel for the same

From what I understand that's normal for multi-plate clutches. Maybe the Nismo is more forgiving than others, don't know. It's not punishing but you have to get used to it. My driving is 80% city and no issues there. Smooth to take off and change gears. Hill starts are mostly fine. It is a bit of a pain for reversing on an incline. I find it hard to get the right amount of clutch slip for that and always end up feeling like I'm burning it too much.

But, you may have a very different experience based on your body type and footwear. With heavy boots or shoes it's likely going to be pretty shit. Just because the clutch is light and the boots don't give enough feel to let the clutch pedal out with precision. Might be similar if you are a big guy or have motor control issues. But able-bodied and driving with decent shoes it feels great.

You don't mention noise at all. It does chatter at idle RPM when it gets warm. Nothing that is out of place in a GTR though IMO.

I agree it's subjective, I'm likely going to have to see if a local owner with a Nismo twin plate or some other twin plate is willing to let me try parking lot maneuvering with their car to really feel confident. But it sounds like for now that's probably the way I'm going. The Nismo clutch is full face organic + copper blend as far as I can tell with a sprung hub and a relatively low spec pressure plate. That's a combination of things that seems like it should stack the deck in its favor. Twin plate is the only hang-up honestly, I've never driven one so I don't know if it's too grabby for me and my poor driving skill.

2 hours ago, GTSBoy said:

Maybe Josh could and should look at that UniClutch thingo too. The street twin one would take the power he's talking about easily. Light action and no noise.

Kind of interesting, but I really don't feel like doing a conversion to push clutch. 

[r32-25t]

Then nismo is your only option 

[soviet_merlin]

10 hours ago, joshuaho96 said:

I agree it's subjective, I'm likely going to have to see if a local owner with a Nismo twin plate or some other twin plate is willing to let me try parking lot maneuvering with their car to really feel confident.

Sounds like a good excuse for a trip to Australia!

But yeah, trying it out is probably the best way to go about it. Please report back what you find.

[joshuaho96]

On 5/22/2024 at 10:41 PM, soviet_merlin said:

Sounds like a good excuse for a trip to Australia!

But yeah, trying it out is probably the best way to go about it. Please report back what you find.

I haven't been able to try a coppermix twin but I tried a 997.2 Turbo 6MT the other day with a single plate organic clutch that had all the springs removed so it's "for race use" and a stronger pressure plate. Absolutely miserable to drive. I couldn't feel the pressure plate weight because the pedal has hydraulic assist from the power steering pump but the slip point felt like I had to flex my big toe to control it because it was so sensitive. The clutch also shuddered horribly at the slip point. My best guess looking at the previous owner documentation is they tried to resurface the dual mass flywheel due to supply chain issues + used a stupid clutch with no marcel springs or any of the usual tricks that trade burst strength for driveability.

I ordered the coppermix twin. Once it gets here I'll try to figure out whether to shop this job out to a local mechanic I can trust or try to DIY it.

[soviet_merlin]

How do you rate the clutch @joshuaho96?

Sometimes I wonder whether it's genuinely very driveable or whether I just feel that way because it cost a good chunk of money. Most recently when seeing the guy at the tyre shop struggle to move the car...

[joshuaho96]

22 hours ago, soviet_merlin said:

How do you rate the clutch @joshuaho96?

Sometimes I wonder whether it's genuinely very driveable or whether I just feel that way because it cost a good chunk of money. Most recently when seeing the guy at the tyre shop struggle to move the car...

It's excellent but I'm still breaking it in so I'm not 100% sure where it'll end up. I would say it's about 15% heavier than stock and the smoothness of the slip zone is quite progressive but you need to be a little patient compared to stock or it'll bite hard and stall. Stock I got away with absolutely horrid clutch control. Like I said before I couldn't even tell where the clutch would grab when it was stock so releasing way too quickly without enough revs it would just slip and the revs would drop lower than ideal but that would be the end of it. Currently there's a bit of a nasty clutch judder if I don't apply enough revs + find the exact wrong point of the slip point in the clutch pedal but it feels like it's slowly resolving as I drive it more.

I would not recommend the competition clutch unless you really need the extra clamp force. I think this clutch combined with the Nismo operating cylinder is going to be exactly what I want. Enough bite that you need to remember the release point to avoid stalling or rough shifts, but progressive enough that it's not hard to drive by any means and not heavy at all.

I tried a "super single" clutch on my friend's 997.2 Turbo 6MT and that was absolutely horrid. It runs an electrohydraulic power steering pump for the clutch power boost so there's zero feedback in the clutch pedal and there was a horrific clutch shudder well after break-in due to the lack of marcel springs or hub springs in the friction disk. It felt like the slip zone was the thickness of a single toe twitch as well so it was almost impossible to avoid stalling it unless you gave it a ton of revs and just dumped the clutch instead of trying to be smooth with it. I was terrified of pulling out in front of traffic.

I have also tried some kind of "super single" on an EK9 and that makes this twin plate Coppermix look like a stock clutch. Releasing the clutch pedal even slightly too quickly feels like you're getting rear-ended. The pedal is extremely heavy as well and there's no vacuum assist like the GTR.