Tilton Twin Carbon Disc Clutches - Turbo & High-Tech Performance Magazine

When price becomes the difference between winning and losing sometimes you just have to bite your lip and fork over the greenbacks. In this industry, racers are realizing that wallets have to be big (and open) to stay on top. Let's put it this way, you just spent thousands of dollars on building your race car and everything seems to be perfect. Horsepower is in the 600-plus range, the chassis is dialed in, the suspension is up to the task and you're ready to hit the track. Let's say you're lucky enough to get in the single digits first time out and you qualify high. The second pass seems to go fine then all of a sudden you smoke your single-disc clutch as you watch your competitor fly by as your single digit potential becomes a 14-second reality. Here is were the dilemma comes in, your two choices are either swap out clutches round after round and pray that they hold up or you fork up the money for something more exotic. One such exotic option is Tilton's new Carbon/Carbon clutch.

Okay so the Tilton unit is pricey but so is the money you could be winning on the track if you could hook up consistently. With horsepower and torque levels still on the rise in the Honda camp it is only a matter of time before single-disc clutch technology will not be able to clamp the power produced on B-series engines. About a year and a half ago I met up with Jason Wahl and Kirk Skaufel from Tilton Engineering at an East Coast race. It was here that they would show me a piece of a puzzle that would come into play soon after. It turns out Christian Rado had a prototype Honda Tilton clutch he was testing. According to Christian, "The clutch has survived over 30 quarter mile runs without service." A year and a half later and now the clutch is available through Tilton.

The Breakdown
The Tilton clutch redefines import clutch technology in various ways. The units use of lightweight material, weight set to the center of the crank and its carbon on carbon construction play a major role on how profoundly this clutch is revolutionizing the import drag race scene.

Taking advantage of lightweight material is a necessity especially in four-cylinder applications. Many have tinkered with various ceramics and iron materials to improve clutch engagement and these efforts have been successful to some degree. The downfall of this approach is unavoidable; it is simply how a limited amount of surface area effects the heat resistance property of the clutch. Excess heat sacrifices holding power. Tilton addressed two fronts with its clutch-using twin discs to increase surface area and using exotic materials for added heat resistance. Tilton decided to use a lightweight carbon material for the following reasons; it's lighter than most other materials and has better wear properties, the clutch cover and pressure plate are made of aluminum, adding to the lightness as well as increasing the strength of the clutch assembly. Unlike most flywheels the Tilton chrome-moly flywheel has no friction contact patch for the drive plates (discs) to ride on. The unit relies on three floater plates to make contact with the number two-drive plate rather having the carbon contact the chrome moly surface. This not only improves the wear properties of the clutch but it also saves time when servicing the clutch. The starter ring gear is also machined into the unit and added perforations aid in cooling of the clutch while reducing weight. The 4140-chrome-moly flywheel is also heat-treated to endure extreme temperatures.

At each step of development the weight of the carbon composite material, the titanium clutch cover and all other materials were considered.

Tilton's Carbon/Carbon clutches for Hondas are available in 185mm diameter which is much smaller than a typical single-disc unit which measures in at 221mm. The smaller size has an effect on an engine's moment of inertia in comparison to an OEM unit. The rotating mass is narrowed down to the center of the crank which allows the engine rev up more freely. The lighter load that the engine has to rotate is not only less than the OEM unit because of the lightweight material used, its moment of inertia is changed due to remaining weight of the clutch being so close to the center of the crank. The weight of a single-disc clutch and OEM flywheel on a B-series Honda is 29.8 lbs. The total weight of the Tilton unit is 12.6 lbs-the difference in these figures make it plain to see the advantages of the Tilton set-up.

Friction material and friction area are also critical concerns when dealing with high-horsepower applications. In the past, and present, different types of material have been used to transfer horsepower to the ground. Along with material concerns the size of clutch disc contact points (i.e. four puck, six puck and full face discs) are important factors. With the Carbon/Carbon unit Tilton relied on carbon composite to provide the necessary clamping force to transfer stratospheric power to the ground. What's different from most single-disc units is the use of a full carbon on carbon contact surface. With most single-disc units, the difference in disc material versus flywheel and pressure plate material tends to distort and cause uneven wear to all the parts. Since the Tilton's floaters and discs are constructed of carbon they share the same heat properties and, in turn, generate an even wear pattern while providing plenty of hook and book force. Even the chrome-moly flywheel and pressure plate becomes a non-friction contact patch due to the two additional floater plates the discs ride on.

One of the best features the clutch has to offer is its surface area coverage. A conventional clutch assembly has two sides of contact, one on the flywheel and one on the pressure plate with the disc in the middle. A twin-disc unit relies on two discs allowing for four areas of contact. This requires use of a floater plate to obtain the additional two surface areas. By bumping up on the surface area of the drive plates they are able to take on more horsepower and torque in the long run.

Streetability
Until now it has been a foregone conclusion that a hardcore race clutch cannot be tamed for the street. Excessive chatter, poor initial engagement and pedal pressures that require a pry bar for engagement combined with the threat of stop-and-go traffic have made the streetable race clutch a mirage of the mind. Until now. High horsepower street machines can harness their power more efficiently with the Tilton Carbon/Carbon clutch. The full-face configuration of the carbon discs, their lack of pads and the result reduction of spring pressure need for engagement take the chatter out of the Tilton clutch. The full face design and light weight of the disc also dispatch abrupt engagement of the clutch. Furthermore, Tilton has moved the fulcrum point on the pressure plate to reduce pedal pressure and enhance the streetability of the clutch. If you have a turbo Honda or other power packed turbo-enhanced street machine and go through clutches quicker than you change your oil, the Tilton unit may be an install it and forget it proposition.

If wining money is what drives you to import drag racing advancing through eliminations is more important than making power. With power levels in the mid to high 600 range it's obvious that driveline parts are going to need to hold up against a tremendous amount of abuse. A great many of the top racers have made their move to the Tilton twin-disc clutch and this tells us that staying on the top of the food chain requires this powerful puzzle piece. As racers experiment with 28-inch, 29-inch and soon 30-inch slicks clutches will be put to even more extremes of heat and torque. Tilton also offers similar triple-disc units for late-model Toyota Supras and will custom design a unit for practically any other type of car. Remember, this is one of the very few race clutches that can gracefully handle street duty.

Since the Tilton clutch has enhanced the moment of intertia by virtue of its lighter weight and improved center of velocity, technically it should not only hook up better but show a gain in horsepower output. Stay tuned for Part 2 of "The Miraacle Clutch" when we put the unit to the test on the dyno.