We recently tested Exedy’s new dual carbon fiber disc clutch. The clutch is a very unique in construction. The clutch uses two specially designed friction discs made from up to 20 layers of carbon fiber sandwiched under extremely high pressure and curred and high temperature. The friction liner is specially designed to have a good coefficient of friction under both regular and hot running temperature. This material also offers high termperature durability as well as limited out gassing and binder material release when the clutch runs very hot to allow the clutch to keep consistant over a broad temperature range. This feature allows the clutch to be intentionally slipped by advanced drivers to manage torque to the wheels during racing. The friction plates are extremely lightweight (about 2 oz.) Each friction plate is driven by a billet carrier hub which sits between the pressure plate and flywheel. The pressure plate uses a unique plate which acts as both a friction contact surface as well as a lever against the diaphragm spring to change the pivot action to allow a high clamping force with out a very stiff clutch pedal. The twin disc design allows the mass to be managed to the center of the clutch minimizing inertia power loss. Each component of the clutch is then precisely rotational balanced. The flywheel is a billet chromoly flywheel with milled outer holes to decrease mass.
The design of the clutch decreases the weight to a little over 16 lbs (compare to a stock 5-speed clutch at 32 lbs).
Part of the testing was to verify compatibility with the 6 speed transmission used in our 1992. The US 6-speed transmission cars use a single disc dual mass flywheel clutch. Unlike the early cars, the standard 6 speed transmission only has only spline set to engage the disc of these clutches. Although the Exedy clutch only has one female spline on the carrier, the position under compression and release of the clutch would allow only 12mm on spline engagement. It was decided to convert the transmission to NSX-R spec. The high performance NSX models in Japan (NSX-R and Type-S) use twin spline input shafts that are designed to be used with a dual plate clutch. It’s amazing that Honda would make this slight but costly modification to an existing part to be able to allow the engineers to couple the superior performance clutch with such limited production vehicles (see picture below).
The input shaft allows any 6-spd transmission equiped NSX owner to take advantage of a multiplate clutch (factory, Exedy, or otherwise). Please see more info below:
http://www.ScienceofSpeed.com/produ...mance_products/NSX/Honda/6spd_twinplateclutch
At the same time, we converted the final drive to the NSX-R 4.23 final drive. US 6-speed transmissions purchased from Honda use a “Torque Reactive Differential”. These differentials build up break away torque between the wheels linearly. The differential uses a different gear cut on the inner planetary gears and inner gear teeth of the ring gear. To install the final drive, a 1991-1994 spec 5-speed differential is required. Although Honda claims greater corner exit speed with the new style differential, the previous “Torque Reactive Differential” was utilized in the new high performance NSX-R. The theory here is that the straight cut gears on these differential react faster to cornering situations where the wheel speed differences are much more dynamic. Either way, a differential was sourced and rebuilt. The NSX-R stopper plate and shim was used to increase the break away torque to NSX-R spec. Once the new input shaft was installed, the clutch could now properly engage the transmission.
The Exedy clutch uses the factory release bearing. The diaphragm spring used by Exedy engages the bearing differently than factory. In order to install the bearing, you must lift the fingers of the spring about 1” upwards. This is difficult to do due to the spring pressure of the diaphragm spring. The best way we have been able to do this is to use 20mm spacers between the flywheel and pressure plate to artificially create a new fulcrum point. Once the fingers are spread open, drop the bearing in, and slowly release the force on the pressure plate. We’d be happy to perform this operation for you in the case that you purchase a clutch and will not be having it installed at our shop.
note bearing does not fit in rested position...
Once the clutch is ready for installation, press the pilot bearing into the flywheel as you would with a factory clutch. The flywheel mounts to the crankshaft in the same manner and with the same bolts as the factory clutch. Make sure that the friction surfaces are free of grease or other contaminants in order to not damage the carbon plates. Take special note to ensure that the balance marks are lined up for perfect balance. Grease the carrier splines and bearing with Honda High Temp Urea grease.
Once installed, the clutch pedal effort is minimally increased over stock. The rate at which the engine spins up is quite impressive, and allows lightening fast rev matching and toe heel downshifts at the track. The designed application for this clutch is for road course track use. Despite using a special formula for the clutch discs to allow smoother engagement over a typical carbon clutch, the design produces noise while the clutch pedal is depressed since the friction discs are unsprung and unmounted. The carbon clutch also produces some shudder when the car is started from a standstill. Despite this, the clutch worked our quite well for our car during NSXPO both on the track as well as on the street in New York.
Overall, we were impressed by the engineering that was placed into the clutch. Although expensive when compared to other clutches, the clutch is much less than other carbon multi plate clutches offered for the NSX and other higher volume sports cars. If you’re in need of the ultimate high performance clutch where engine speed and response is the top priority for your track driven NSX, the Exedy Multi-Plate Carbon Clutch is a strong candidate.
Please find more information and photos here:
http://www.scienceofspeed.com/products/drivetrain_performance_products/NSX/Exedy/clutch_set/
Thanks for the guys at Exedy for the help and an outstanding product!
Cheers,
-- Chris
The design of the clutch decreases the weight to a little over 16 lbs (compare to a stock 5-speed clutch at 32 lbs).
Part of the testing was to verify compatibility with the 6 speed transmission used in our 1992. The US 6-speed transmission cars use a single disc dual mass flywheel clutch. Unlike the early cars, the standard 6 speed transmission only has only spline set to engage the disc of these clutches. Although the Exedy clutch only has one female spline on the carrier, the position under compression and release of the clutch would allow only 12mm on spline engagement. It was decided to convert the transmission to NSX-R spec. The high performance NSX models in Japan (NSX-R and Type-S) use twin spline input shafts that are designed to be used with a dual plate clutch. It’s amazing that Honda would make this slight but costly modification to an existing part to be able to allow the engineers to couple the superior performance clutch with such limited production vehicles (see picture below).
The input shaft allows any 6-spd transmission equiped NSX owner to take advantage of a multiplate clutch (factory, Exedy, or otherwise). Please see more info below:
http://www.ScienceofSpeed.com/produ...mance_products/NSX/Honda/6spd_twinplateclutch
At the same time, we converted the final drive to the NSX-R 4.23 final drive. US 6-speed transmissions purchased from Honda use a “Torque Reactive Differential”. These differentials build up break away torque between the wheels linearly. The differential uses a different gear cut on the inner planetary gears and inner gear teeth of the ring gear. To install the final drive, a 1991-1994 spec 5-speed differential is required. Although Honda claims greater corner exit speed with the new style differential, the previous “Torque Reactive Differential” was utilized in the new high performance NSX-R. The theory here is that the straight cut gears on these differential react faster to cornering situations where the wheel speed differences are much more dynamic. Either way, a differential was sourced and rebuilt. The NSX-R stopper plate and shim was used to increase the break away torque to NSX-R spec. Once the new input shaft was installed, the clutch could now properly engage the transmission.
The Exedy clutch uses the factory release bearing. The diaphragm spring used by Exedy engages the bearing differently than factory. In order to install the bearing, you must lift the fingers of the spring about 1” upwards. This is difficult to do due to the spring pressure of the diaphragm spring. The best way we have been able to do this is to use 20mm spacers between the flywheel and pressure plate to artificially create a new fulcrum point. Once the fingers are spread open, drop the bearing in, and slowly release the force on the pressure plate. We’d be happy to perform this operation for you in the case that you purchase a clutch and will not be having it installed at our shop.
note bearing does not fit in rested position...
Once the clutch is ready for installation, press the pilot bearing into the flywheel as you would with a factory clutch. The flywheel mounts to the crankshaft in the same manner and with the same bolts as the factory clutch. Make sure that the friction surfaces are free of grease or other contaminants in order to not damage the carbon plates. Take special note to ensure that the balance marks are lined up for perfect balance. Grease the carrier splines and bearing with Honda High Temp Urea grease.
Once installed, the clutch pedal effort is minimally increased over stock. The rate at which the engine spins up is quite impressive, and allows lightening fast rev matching and toe heel downshifts at the track. The designed application for this clutch is for road course track use. Despite using a special formula for the clutch discs to allow smoother engagement over a typical carbon clutch, the design produces noise while the clutch pedal is depressed since the friction discs are unsprung and unmounted. The carbon clutch also produces some shudder when the car is started from a standstill. Despite this, the clutch worked our quite well for our car during NSXPO both on the track as well as on the street in New York.
Overall, we were impressed by the engineering that was placed into the clutch. Although expensive when compared to other clutches, the clutch is much less than other carbon multi plate clutches offered for the NSX and other higher volume sports cars. If you’re in need of the ultimate high performance clutch where engine speed and response is the top priority for your track driven NSX, the Exedy Multi-Plate Carbon Clutch is a strong candidate.
Please find more information and photos here:
http://www.scienceofspeed.com/products/drivetrain_performance_products/NSX/Exedy/clutch_set/
Thanks for the guys at Exedy for the help and an outstanding product!
Cheers,
-- Chris
How long of a life could it possible have??? hehe
