I've gotten some questions and PM's on the OS Giken STR2C twin disc clutch. Here's a quick review after about 300 miles of break-in driving. In a nutshell this is the best clutch I've ever tried in the NSX. Billy has this in his personal car so please correct me if you disagree with anything stated here. It's subjective and opinions are always open to debate.
Here are other clutches I've tried.
* stock 5spd
* stock 6spd
* Clutchmasters FX300 single kevlar multi-puck
* RPS Single
* RPS/SOS Twin Carbon
* SOS 275 (Or whatever they call their "Sport" clutch)
* Exedy twin
* Exedy single
* Notable mention to the Comptech Power Grip which I have NOT tried.
Build Quality - 9/10. The machine is work is outstanding but i'm on the fence about whether or not they could have made the flywheel lighter.
Pedal Pressure - Positive and a tiny bit lighter than stock. I owned a stock 5spd 91 NSX recently so it was easy to compare back to back. The stock is more springy and more dampened. You couldn't feel the engagement thru your left foot but instead rely on your other senses to feel the car moving or the engine lowering in RPM as clutch engages. The OSG is much more crisp, positive, and not springy. It's consistent in pedal pressure throughout the pedal travel but with a slightly narrower sweet spot before the clutch fully engages. It also doesn't engage as high a stock clutch. It feels appropriate for a sports car (not a race car). I'm of the opinion that the OSG pressure plate is actually very heavy (for high HP) but their slave cylinder "Alteration Kit" add more leverage so it feels like stock. Great engineering.
Engagement - I'm very impressed with the engagement. I could talk about it for a long time but won't. Suffice to say it's easy to modulate and there's virtually no chatter (but you can make it chatter if you try). It's very easy to sense where the catch point is and it's more sensitive, in a good way, than stock or my Clutchmasters for that matter. The metalic disc have an interesting nature to it. It will allow for some smooth slippage when you're taking your GF to a nice dinner and don't want to pin her head to the headrest and induce whiplash but if you slam the clutch it responds like an ON/OFF switch as well and you can tell your motor mounts are working hard. It's dual nature in that way. I'm very impressed.
Noise - It does make noise when the clutch pedal is depressed for that short moment in time. Some kid thought my car was broken but it not loud and offensive like the Exedy version. Perhaps once I get more miles it will get louder. If you WPC the friction plates the noise is actually lower. I'll also drive a few other NSXs with and without the WPC treatment on their STR2C in the coming months for more comments. CDX_NSX just got his installed and he's got about the same amount of miles on his but he's got a 500wHP motor.
Torque Holding Capacity - I'm noticing no issues at all with my CTSC but a track day will be more telling.
MOI or Rev-eagerness - 7/10. I don't notice any difference from the Clutchmasters I had though I am supercharged so spinning the compressor will dull my revs already. I feel like the SOS Twin Carbon is more rev happy however I stalled that car twice and i'm not a rookie driver so it comes with some expense to daily driving imo. The STR2C is a good street/track clutch which suits my car.
Anyway, I'm a fan if you can't already tell.
