Motovicity's Ticket To Ride FR-S Update- Exedy Stage 2 Clutch
By Mike Kojima
In anticipation of more added power to the Motovicity Ticket to Ride FR-S from the HKS Supercharger it was decided to also upgrade the clutch. What we wanted is something that could take the abuse of the extra power and doing some occasional drift clutch kicking fun while maintaining as much daily driven ability as possible.
This is a difficult compromise. Usually a dual purpose street heavy duty clutch uses a softer organic friction material in the clutch disc, but with the FR-S naturally wanting to drift being rear wheel drive we felt that an organic disc would soon succumb to the abuse of clutch kicks.
A puck type disc with metallic friction material usually works well for this application, but metallic disks typically lack streetability wanting to chatter and are grabby with a tendency to stall. Both of which would definitely not be fun in traffic.
For the value of both the ability to stand up to abuse and retain some driveability, we selected the Exedy Stage 2 Cerametallic clutch kit. The Exedy Stage 2 is an excellent compromise that bridges the gap between a full race clutch and a heavy duty clutch. Let us show you how.
The Exedy pressure plate is a conventional looking diaphragm type similar to the OEM part, but it is tweaked for performance use. The pressure plate has 1,652 lbs. of clamping force which is up about 40 percent from stock. To keep the pedal effort from getting too high, the fulcrum point inside the pressure plate housing has been moved outward so the throwout bearing has more leverage on the stiffer than stock diaphragm spring. This step is often forgotten about on other clutches resulting in a sore leg. Moving the fulcrum also spreads out the engagement point over a longer portion of the clutch pedal travel making a hard grabbing clutch more progressive and easier to drive.
The pressure ring is an OEM type model of heat and burst resisting nodular iron attached to the pressure plate cover with reinforced drive straps. The round wire ring is the pressure plate diaphragm spring fulcrum we were talking about above.
As a nice touch, the diaphragm fingers are induction hardened where they rub the throwout bearing for longer life.
The Exedy Stage II clutch disc is a hard grabbing 3 puck with ceramic metallic, or cerametallic, friction material. Fewer pucks mean that the harder and more aggressive friction material is loaded harder per square inch than having more pucks so the amount of grip goes up with this sort of material. Having fewer pucks means less rotating inertia which makes for faster shifting and less stress on syncros. The pucks are bonded to a copper plate which conducts heat away from them faster. The disc is a generous 225mm in diameter which is the same size as a 350Z for instance.
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