RPS Sport Clutch kits have a great upgrade in holding power coupled with smooth engagement characteristics and driveability. Most with minimal pedal pressure increase for your daily driving needs. Ideal for bolt on performance upgrades (BPU) such as air intake, exhaust system, ignition system, fuel system and adjustable cam gears. Available with Street disc, 6-Puck Solid and 6-Puck Sprung Hub discs. Use 6-Puck discs for racing.

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RPS Sport Clutches

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Some good reading from RPS:

Clutches are basically made up of two parts: the pressure plate (clutch cover) and the clutch disc. A clutch’s main purpose in life is to smoothly transfer the engine's power to the wheels. The following is the actual formula used to calculate the amount of torque the clutch system can transfer.

Clutch Torque Capacity:
Pressure plate strength, times clutch disc size, times the number of clutch discs, times the friction coefficient, divided by a constant.

By looking at this equation, we can see that torque capacity increases by doing any of the following: increase the strength of the pressure plate, increase the size of the disc, install more discs, or increase the coefficient of friction of the disc(s). In most cases, it is not practical to install a larger clutch or go to a double or triple disc setup, so the two areas a clutch engineer has to play with is making the pressure plate stronger and increasing the coefficient of the disc.

Mechanically it is important to understand how a clutch is attached to the engine. The pressure plate is bolted to the flywheel and the flywheel is bolted to the crankshaft, therefore the flywheel, pressure plate and crankshaft all turn as one.
The clutch disc has a hole in the middle with splines which slides over the transmission's main input shaft. All of the engine's torque is transmitted though the clutch disc to the transmission and then to the wheels.

When the clutch is engaged, the pressure plate squeezes the disc against the flywheel making the disc rotate at the same speed as the engine. When the driver presses down on the clutch pedal to disengage the clutch, the casting surface of the pressure plate (the surface that the disc rides against) pulls away from the disc and releases the disc from the flywheel. The flywheel still spins, but the disc and the transmission input shaft do not. This is why a car can be stopped with the engine running while in gear.

Going back to the above equation, if we increase the clamping force of the pressure plate, then we increase the torque capacity of the clutch system. Almost all of the pressure plates used today use a diaphragm spring to exert their clamping force. Over the years clutch companies have tried various ways to increase clamping force. One of the most recognizable methods is using the centrifugal force of weights attached to the fingers of the diaphragm spring. There have been many arguments over the years if this technique really works or is it just great marketing at work. There is no reason to get into the debate here, except to explain how to test the theory yourself.

The faster the weights spin, the higher the centrifugal force. If the force is directed in the direction of pulling back on the diaphragm fingers, then the clamping force will go up. To test if the force is in the right direction, pump the clutch pedal at idle and feel how stiff the pedal is. Then rev the engine to near redline and pump the pedal again.
If the centrifugal force is pulling back on the fingers, then the pedal will be stiffer at the higher RPM.

Another old-time method of increasing pressure plate pressure is to move the fulcrum point or pivot point that the diaphragm spring rides against. The spring acts as a lever with the pivot point of the lever being the fulcrum. With the help of leverage, a lever allows you to lift a heavier object than without leverage. Moving the pivot point closer to the object requires more movement at the other end (longer stroke), but gives you more leverage.
So the only down side to more leverage is a longer stroke. When you move the fulcrum point in a pressure plate you get more clamping force, but you also have to stroke the clutch pedal farther to get it to disengage. Poor release characteristics are the most common complaint you will get when using a pressure plate that has had the fulcrum point moved.

The RPS method developed in the 90's to increase pressure plate pressure was to re-shape the diaphragm spring producing a higher spring force. This method has been so successful that it has been patented. When re-shaping a diaphragm spring it is critical that the original shape has been "erased" from the metal's "memory". Re-shaping the spring without employing RPS’s patented step to eliminate the memory, will over time result in the spring bending back into its original shape.

Most RPS “Max” Turbo Clutches use a push type, progressive dual diaphram technology. This innovative technology gives the pressure plate maximum release, less diaphram friction, serious holding power with smooth engagement, and custom Pressure Plate build-up available in 100 lbs increments. Turbo Clutch also applies a patented 7 stage heat treatment to all pull style “Max” pressure plates. This allows the diaphram to have the highest clamp load after prolonged use without sacrificing good release or durability.

Another process that clutch engineers can employ is changing the clutch disc’s coefficient of friction which raises the torque capacity. However, the problem most engineers have is that there are only a few clutch disc manufacturers in the world. Most of the aftermarket performance clutch manufacturers like Centerforce, Ram, Mcleod, Zoom and others can only buy the same friction materials from the same manufacturers.

"Dual friction" or "puck" style clutches use either cut pieces of factory material or ceramic or Kevlar segments. The up side of the puck design is better holding power. The reason for the better holding power is the pucks have about half of the surface area of a full circle disc so the pressure plate pressure is distributed over a smaller area.
Pounds per square inch (PSI) can be increased by leaving the pressure the same and decreasing the square inches of contact. Of course the less clutch material you have the faster the clutch wears out.

The down side of ceramic pucks is they not only wear themselves out, but they can be hard on the flywheel surface. Aftermarket FW's (flywheels) have many friction metals, each with their own unique coefficient that the disc mates to. Cromoly FW’s are durable in structure and are lightweight but the material is hard on the “Rockwell Scale.” This causes the friction surface to lose it's coefficient of friction grip and cause more slippage than normal O.E.M. cast iron. The same applies to heat treated steel friction inserts.

The most advanced friction material known to man is Carbon-Carbon. Carbon-carbon composites consist of highly-ordered graphite fibers embedded in a carbon matrix. C-C composites are made by gradually building up a carbon matrix on a fiber preform through a series of impregnation and pyrolysis steps or chemical vapor deposition. C-C composites tend to be stiffer, stronger and lighter than steel or other metals. The most important class of properties of carbon-carbon composites is their thermal properties. C-C composites have very low thermal expansion coefficients, making them dimensionally stable at a wide range of temperatures, and they have high thermal conductivity. C-C composites retain mechanical properties even at temperatures (in non-oxidizing atmospheres) above 2000°C. They are also highly resistant to thermal shock or fracture due to rapid and extreme changes in temperature.

There is a lot of confusion about other “Carbon” clutches available today. Exedy or OS Giken or ATS (and anyone else except for Tilton) are all using (CarbonClaw) technology created by RPS 5 years ago. This carbon/ceramic mixture gives a higher coefficient than other friction materials available to most manufacturers. Semi-Carbon (the true name of this material) can be very costly to manufacture because the friction mating surface is metal. Semi-carbon discs are more streetable than many other materials when heated up, but will not hold up to the higher torque/boost, causing slip. The affect is still the same as conventional clutches; they will not hold up to excess heat and will glaze over if slipped too much. Simply put, this technology is still a long way from the “Real McCoy” of RPS Carbon-Carbon. This is the only stuff that NASA, F-1, Top Fuel, WRC, and NASCAR use.

Our “hard core” racer clients who using our C-C technology are using our break-through technology to do 2nd gear burnouts, 2nd gear launches, and even line lock assisted launches with the clutch semi-disengaged to load the engine to make positive boost (15~30 psi) in 2nd gear!!! Others do 1st gear, 7000+ RPM clutch dumps controlling traction by slipping the clutch for a fraction of a second. All this on cars like 2-ton 750+AWHP cars making 200+ passes on top of daily driving (3000GT-VR-4 Dynamic Racing); dyno slipping MKIV Supras with 1200lbs of torque (Powerhouse/MVP); daily driven Supercharged Viper GTS’s cranking out 1000lbs of torque (Palo Castalano/ Heffner Performance.)

Currently Carbon-Carbon clutch technology is only available from RPS Performance Products.

 

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