Replacing Project Evo X's worn-out stock clutch with another stock clutch would be evidence of insanity. Clearly, the Garrett upgrade turbo will require a clutch with more torque-handling capability.
We're picky, though. Project Evo X is not a full-on race car, so the clutch needs to have smooth engagement and minimal noise. That rules out solid-hub discs, which can transmit gear noise. It also rules out puck-type cerametallic discs which judder like crazy every time you engage the clutch.
So, yeah, we want our clutch to do it all. Hit the jump for the lowdown.
Changing clutches isn't something we pine to do, so we went to the west coast's Evo nexus--Road Race Engineering in Santa Fe Springs, CA--where the dirty work was for done for us.
You might remember RRE--they installed and tuned Project Evo X's Cosworth cams.
And it is a sight. Evos are everywhere at RRE--from a RHD Evo V to an armada of Evo VIIIs and IXs, plus a half-dozen Evo Xs. Yeah, we're in good hands.
The next obstacle was which clutch to choose. It turns out Advanced Clutch Technology of Palmdale, CA, offers a range of clutches for the Evo X that can handle any engine torque from stock up to 734 lb-ft. That should be sufficient.
In the end, we settled on ACT's ME1-HDSS clutch. This clutch includes a disc that has a sprung hub (see yellow springs) with an organic lining, like the stock one.
The disc alone is good for a smidge more torque capacity than stock, but it is the pressure plate that really ups the ante.
The ACT HD pressure plate adds 42% more clamping force than stock, bringing the clutch's torque-handling capability to 512 lb-ft. This will be as civilized as possible while still provided plenty of overhead capacity.
Pedal effort will increase a bit compared to stock. Should be fine--our stock pressure plate grew heavier over time, so our quads are already primed.
We noticed that hard launches have taken their toll on the stock flywheel. Blued and heatchecked, it's still serviceable but the "while you're in there" syndrome kicked in. We decided to have it replaced with a lighter-weight ACT Streetlite flywheel to sharpen up the throttle response in lower gears.
Aluminum flywheels are no bueno in our experience. They need to be multi-piece--a steel friction surface, steel ring gear and the aluminum body--and we don't want to take any chances with warpage of the insert or separation, plus we've had bad experiences with aluminum flywheels' tendency to pull threads. The Streetlite is a one-piece forged chromoly steel unit. Problem solved.
Past experience suggests this should still be a streetable affair. It weighs about a pound less than stock, which doesn't sound like a lot until you consider that inertia increases with the square of the radius. A little meat removed from the largest possible diameter goes a long way.
Note the pockets at the outer edge of the Streetlite unit. Someone at ACT was paying attention in physics class.
ACT ME1-HDSS clutch: $755
ACT XACT Streetlite flywheel: $356
Jason Kavanagh, Engineering Editor
cwmoo740 says:
05:20 PM, 08/20/09
More expensive toys. How close are you to the price of the GT-R now?
hybris says:
06:20 PM, 08/20/09
So when are you guys going to bore and stroke the block or get it blueprinted?
orangutan says:
06:58 PM, 08/20/09
Are those prices including installation? If not, how much for that?
e10rice says:
07:03 PM, 08/20/09
My thought exactly orangutan. they cant be with labor. Those have to be just the parts.
ahightower says:
05:31 AM, 08/21/09
So cool. You've got to keep the GT-R long enough to do a detailed comparison test of the two when you're finally done modding the Evo. I suspect we're still nowhere near the cost of the GT-R. Especially if you don't count all the GT-R's warranty repairs as "free".
e10rice says:
07:12 AM, 08/21/09
But if the GT-R warrenty repairs are free whats the problem, no money was paid out.
stingray454 says:
08:40 AM, 08/21/09
Not that expensive for what looks like well engineered parts. Should be a nice and needed upgrade.
Do they make twin disc clutches for this car?
joefrompa says:
08:50 AM, 08/21/09
e10rice - Check out the maintenance costs of the GT-R.
Edmunds - Isn't the standard "reserve capacity" of a clutch supposed to be ~20-30% over your engine's output? Do you think you'll have that much reserve?
Be very curious to see what you think of the driveability of this setup. Although I'm very surprised by one thing: 1 pound less than stock? That doesn't seem right to me. I understand the polar moment of inertia stuff, but for marketing reasons alone I'd expect them to cut out a few more pounds.
Joe
ahightower says:
01:07 PM, 08/21/09
"But if the GT-R warrenty repairs are free whats the problem, no money was paid out."
Because they won't be free forever. If you're going to drive a high performance car like it was meant to be driven, then you must expect significant some maintenance costs. Maybe the things the dealer fixed on the GT-R will never fail again...
tarmacdaddy says:
04:05 PM, 08/24/09
i had the same setup on my evo viii done from rre as well. they do solid work. the clutch pedal travel was reduced and it definitely took a bit more calf muscle to work it, but man did that clutch perform. the bite was so hard that everytime i dropped clutch when speed-shifting, it felt like i got rear-ended from the strong engagement.
man, i would love to take your project evo for a hot lap anywhere. feel like trading it with an mildly suped up x mr for a day? :-p
ddevox says:
01:37 PM, 08/26/09
Should have gone with the exedy twin metalic clutch. The HD ACTs are recking havoc on the clutch master in these cars. At least buy and install the AMS Mitsubishi Lancer Evolution X Clutch Master Cylinder Reinforcement Ring unless you liked a cracked clutch master.
And the stock clutch is designed to be the "weak link" in the car. As the car is designed purposefully to be able to handle significant added horespower mitsubishi needs to protect themeselves somehow. A weak clutch makes it necessary to upgrade your clutch if you want to modify the car. Who cares though, replace the clutch once and you already have a gear box and drivetrain that can handle stock in excess of 500whp.