Part of making big power is having the proper means of putting the power to the pavement. It goes without saying that a stock clutch isn’t going to handle making nearly three times more horsepower, but when it comes to clutches that can handle the power, drivability starts to become the gray area. That area can now look a little more blue thanks to Centerforce and their DYAD twin disk clutch technology.
Cameron Prause, the Southern California owner of this sweet ‘Stang, built the ride up to make sure that it’s performance matched its smooth looks. The 2006 GT’s 4.6-liter engine had previously been overhauled with a forged Cobra crankshaft, forged Manley H-beam connecting rods and pistons to make sure the internals were strong enough for the polished 2.6-liter Kenne Bell supercharger that would sit on top.
Complimenting the Kenne Bell installation were Ford Racing cams, an AFCO dual pass heat exchanger, 60 pound fuel injectors, GT500 fuel pump and American Racing long tubes. When all was completed and tuned, the end results were impressive to say the least. On an engine dyno, the modified V8 pounded out 650 peak horsepower and 610 ft-lb of torque.
We first started building twin disc clutches in the 1980s, but the problem was, there wasn’t many street cars during this era that produced enough power to need a twin disk clutch.
When installed back in the Mustang, an aftermarket clutch was added to the otherwise stock drivetrain, but it wasn’t long after that when the troubles started. Getting power to the pavement depends on a number of components doing their job right, but just like a chain, it can only be as strong as the weakest link.
The Mustang runs a staggered tire setup, with 20 x 8-inch Bose forged alloy wheels in front and 10-inch wide versions out back. Shod with massive 285/30ZR20 BF Goodrich KDW tires, the back end was doing its part in getting the power through. Unfortunately, it wasn’t long before the single plate clutch began slipping on hard acceleration and something needed to be done.
The Dual Disk Phenomenon
Dual disk clutches first found application in the contemporary Shelby GT500. Previously reserved for use on ultra high performance vehicles, the benefits of the dual disc design apply equally to hard charging Mustangs. Offering higher torque handling capacity without an equal increase in pedal effort, the dual design also maintains smooth engagement and driver control. “We first started building twin disc clutches in the 1980s, but the problem was, there wasn’t many street cars during this era that produced enough power to need a twin disc clutch,” said Will Baty of Centerforce. “Now vehicles come with 400 horsepower from the factory and now weigh a lot more, so the demand resurfaced.”
The design approach is rather simple, needing only a small increase in mechanical complexity to achieve these benefits. A standard, single plate clutch works by squeezing the clutch disc that is attached to the transmission, between the engine flywheel and the clutch’s pressure plate. The clutch disc has friction material on both sides and the ultimate torque handling capacity depends on that material plus the clamping force that can be generated by the pressure plate.
Getting more torque capacity is a balancing act of epic proportions and some pretty extreme measures have been taken in the past. Changing the friction material can yield better results, even to the extent of using sintered iron pads, but the impact on drivability is extreme. This is a competition-only solution. “When you are making over 500-600 horsepower, people should start considering a twin disc clutch,” explained Baty. “Most people don’t stop there and want to make even more power, and the DYAD will handle virtually anything you can throw at it.”
Increasing the contact area between the clutch disc and the flywheel is another approach, but physical limitations exist, so this can only go so far. Keeping the weight of rotating components low is a priority as well. If the clamping force is increased. typically by using stronger springs in the pressure plate, the pedal effort to release the clutch increases as well.
We wanted to go with a positive drive floater type clutch system because it’s already a proven technology that we see in Top Fuel cars.
Once we throw away the idea of only being able to have one clutch disc, a whole new world of possibilities opens up. First, with two clutch discs, we now have four friction surfaces to work with. Clamping forces can be reduced since they are applied to four surfaces, so pedal effort no longer requires steroid injections in your left leg. “A single disc can hold the power in a lot of circumstances, they just don’t hold it for very long,” said Baty. ” With a twin disc, you have twice the material and surface area to distribute that power.”
The arrangement of components is only a little more complex, as shown in the diagram. The pressure plate is almost unchanged, except it is deeper to handle the extra clutch disc and floater plate. The two clutch discs are connected by drive pins and the floater plate sits between them. The drive pins allow the clutch discs to turn as one, but lets them move axially to release their grip and to accommodate disc wear. “We wanted to go with a positive drive floater type clutch system because it’s already a proven technology that we see in Top Fuel cars,” mentioned Baty.
Beyond all this, the overall clutch design can be more compact, using smaller diameter discs and components which reduce driveline inertia. The benefits just don’t stop coming.
Centerforce DYAD 2005-2010 Mustang Clutch PN 04114805
• Fully dampened clutch system designed for vehicles with extreme power levels
• Smooth engagement and light pedal effort
• High torque capacity – 1300 lb/ft at the flywheel
• All ARP fasteners
• Specification dyno card included
Application and Install Notes
For our install, we turned to the folks at Centerforce and their DYAD product which is well suited for this particular pony. With a limit of 1300 ft-lb flywheel torque, this clutch wasn’t about the be overwhelmed by the supercharged engine’s output.
The Arizona company has products for all Mustang modular motor applications since 1996. Both 6-bolt (cast) and 8-bolt (forged) crankshaft variants are covered on the 4.6-liter V8, as well as the 2006-2009 supercharged 5.4-liter GT500 engine and now the 2011+ 5.0-liter engine as well.
Installation, as we’ll see in the accompanying photos, is virtually no different than for a standard, single disc clutch and is a direct bolt-in replacement for the original clutch. No special modifications are required. Swing by the powerTV garage now as we perform a little clutch swapping exercise.
Results That Shout for Themselves
Short and simple, the first time out after break in with the new Centerforce DYAD clutch installed, getting that 610 ft-lb of torque past the clutch was no problem at all. “For breaking the clutch in, I recommend 500 normal and easy miles,” Baty recommends. “Try to keep away from full throttle runs. You don’t want to generate a lot of heat, but you want to seat that friction material in by bedding that material into all the metal surfaces in that clutch.” Unfortunately, passing that motive force through the stock transmission became the next challenge. As you’ll see in the photo, the transmission’s input shaft surrendered in a pretty spectacular fashion as a result.
Swapping that carnage out for a GT500 six-speed gearbox resolved the torque limit issue and a Powerhouse one-piece aluminum driveshaft looks after connecting the gearbox to the GT’s rear axle. All in all, this Mustang now delivers on the promise that its good looks make. The chatter that we previously experienced with the original clutch is completely gone, plus the need to have a strong left leg to push it the clutch pedal in is no longer needed.
Centerforce’s DYAD technology really does work. The twin disc design doubles the surface area available for the engine to transmit its power, which allows Centerforce to reduce the harshness of materials used; this is what makes this clutch last while harnessing tons of power. The drive lug design locks both clutch discs together and completely eliminates chatter and clutch noise. No longer was the clutch the weak link in this drivetrain and we paid the price of a broken input shaft when all the power was actually transmitted to the rear wheels.
It is a bit amazing that the Centerforce clutch can handle this amount of torque because it drives exactly like a stock Mustang – now your girlfriend can take it to work without the worrying about a cloud of clutch smoke following her. Looking to make more power down the road? No problem, this clutch will take it while laughing at you to bring more. An admirable balance of show and go have been built up and that makes this pony a smooth operator.