Subaru WRX 2008, Stage 4 Racing Clutch Kit by EXEDY®. Disc Outer Diameter: 200mm. Number of Discs: 2. Add more torque capacity to your clutch assembly to handle the extra load of a highly modified engine. These two-plate clutches are designed for high power street driving as well as drag, road racing and rallying.
Notes: SFI 1.1 Approved - Certified for use in Competitive Motorsports.
- Double the torque capacity with dual friction plates
- More friction area means a smaller diameter assembly for less inertia
- Quicker shifts and faster lap times
- All multi-plate clutch kits come with lightweight chromoly flywheel
- Purple anodized forged aluminum cover
- Strap or lug drive, depending on application
- SFI approved for racing
- Spring damper discs or solid discs
- Cerametallic or carbon friction material
If you've modified your engine and substantially boosted horsepower and torque, a single-plate clutch may simply be inadequate to prevent slippage under full throttle. EXEDY has the solution for engines that deliver as much as 500 lbs.-ft. of torque by doubling the number of plates. The extra friction area also permits using a smaller-diameter assembly for less inertia. The heaviest components of the clutch system are the clutch cover, plates and flywheel. Low-inertia discs allow the transmission to synchronize in a shorter interval of time, eliminating time loss during shift changing while also reducing stress on drivetrain components. The weight of a carbon clutch disc is one third that of a metallic disc.
For most streetable applications, the preferred clutch disc is the cerametallic style with a damper hub. This style of disc will have a consistent feel throughout the day, from the first cold start of the day to a launch from the Christmas Tree after a heat-inducing burnout. The damper hub will help with a smooth launch and improved gearchange feel, as well as eliminate gear rattle moderate speeds. Gear rattle is caused by variations in crankshaft rotational speed, as individual cylinders fire. That in turn makes the gear teeth bounce and rattle against each other as you head on down the road.
A more ambitiously-modified vehicle, used mostly for drag racing, autocrossing or rallying might benefit from the use of a Carbon-D friction disc, Faced with pure carbon fiber, laid one strand at a time and baked at 3600° to cure, carbon fiber has an interesting characteristic: it's coefficient of friction (COF) gets higher as it gets hotter. Unfortunately, it's inconveniently low when at room temperatures, rising to the same COF range as cerametallic friction material when warmed properly. Used in a street vehicle, its inconsistent takeup may be annoying in a daily driver. Carbon fiber is very long-lived in heavy-duty use, however. Carbon-D friction discs have a spring-dampener hub for easy shifting and quiet gears. Carbon-D is equipped with a new dual stage damper, a low-load stage and rapid-acceleration stage, both of which are individually tuned for each car type.
For a dedicated race or track car, Carbon-R friction is preferred. The lack of a dampener hub may mean a fair amount of harshness, vibration and noise may intrude into the cabin or be felt in the gearshift or clutch pedal. The dampened hub, combined with the lighter weight of the whole assembly may make stating up difficult to do without some initial judder. The advantages in shifting speed and torque capacity are the payoff for this lack of refinement.
Due to the inherent properties of the carbon material, EXEDY suggests the proper way to bring the discs up to operating temperature.. The correct method is three sequential five second "slips" of the clutch within 30 seconds at low RPM. This will heat the discs so they will hold the specified torque rating
EXEDY® is a global leader in the clutch business, with hundreds of applications, many of them still bearing their original Daikin logo. Well-respected, and with a huge share of the OEM clutch industry, EXEDY has become a leader in the motorsports field, pioneering new technologies like puller clutch springs and carbon-fiber friction material. With roots going back to 1923, EXEDY manufactures globally, but has a major presence in the US, with several domestic facilities manufacturing clutch components for applications here and for export.