lor:
Off-topic:what's the status of PCCC ceramic clutch development-does it belong to history now double-clutch gearboxes are the new standard or is Porsche still working on it?I would like to see that make its way to 991GT3/RS...
2010 PORSCHE 911 GT3 R
Dr. Ing. h.c. F. Porsche AG, Stuttgart, keeps the focus on customer racing during the 2010 motorsport season. The new Porsche 911 GT3 R, delivered to customers ready-to-race, replaces the 911 GT3 Cup S in Porsche Motorsports' model range. The 911 GT3 R will be raced in series based on international FIA GT3 regulations. In developing the vehicle, the emphasis was placed on improving driveability and making handling easier. The 911 GT3 R features a four-litre six-cylinder boxer engine delivering 480 hp (353 kW). A six-speed sequential gearbox transmits the power to the rear axle.
The most important facts and figures:
- single-seated, near-standard race vehicle
- 4.0-litre six-cylinder horizontally-opposed power unit developing 480 bhp (353 kW)
- sequential six-speed manual gearbox
- weight 1,200 kg (2,646 lb)
The new 911 GT3 R celebrated its world debut on 14th January 2010 at the Racing Car Show Autosport International in Birmingham (Great Britain).
The development of the 1,200 kg lightweight 911 GT3 R is based on the Porsche 911 GT3 Cup presented in September 2009 for one-make cup racing. Thanks to a 0.2-litre increase in engine capacity, the GT3 R delivers 30 hp more than its Cup pendant. Both race vehicles are based on the extra-wide body of the street-legal 911 GT3 RS. The rear air dam with its striking air vent openings as well as the rear lights in LED technology, in turn, come also straight from the road model.
An anti-lock brake system (ABS), traction control and an e-gas with "throttle-blip" function help pilots familiarise themselves quicker to the new GT3 race vehicle compared to its predecessor, also making it easier for ambitious amateur racers to get used to the car. The flared wheel arches front and rear show the wider track compared to the previous model. The underbody of the vehicle is completely covered and features a rear diffuser. Compared to the forerunner model, the adjustment range of the rear wing has been increased.
The highly developed race suspension can be extensively adjusted: At the front are height-adjustable McPherson struts with variable SACHS two-way shock absorbers and double coil springs (main and auxiliary). At the rear, the GT3 R features a rigidly mounted sub-frame with a height-adjustable multi-arm axle, as well as adjustable SACHS two-way shock absorbers and double coil springs.
2010 PORSCHE 911 GT3 R: POWERTRAIN
- Porsche 6-speed sequential dog gearbox with active oil cooling and internal pressurized oil lubrication system
- Gear ratios:
Drop Gear 25/32 1,280
CW & P 09/26 2,889
1st gear 13/41 i = 3,154
2nd gear 17/39 i = 2,294
3rd gear 20/37 i = 1,850
4th gear 23/35 i = 1,522
5th gear 22/28 i = 1,273
6th gear 31/34 i = 0,931
- Limited slip differential 37% drive / 52% overrun
- Single mass flywheel
- Race clutch (5½" triple plate carbon clutch)
- Hydraulic release bearing
- Oil-water heat exchanger
- Rear wheel drive
PORSCHE CARRERA GT -- CLUTCH TECHNOLOGY
In the Porsche Carrera GT, not only the brake pads grasp onto ceramic plates. The clutch, too, finds its power connection on this enormously hard silicon carbide. A new technology with far-reaching consequences.
Power is transferred to the rear wheels through a newly developed six-speed manual transmission. Attached is a special clutch which has a reduced size and weight. Called Porsche Ceramic Composite Clutch (PCCC), this two-plate clutch is made of ceramic composites.
The most powerful of all production Porsche cars is different from its siblings in one aspect that directly involves pure power: the so enormously powerful Carrera GT, with its 612 bhp (450 kW), has the daintiest clutch of any Porsche. The diameter of the clutch plates, 169 millimeters (6.65 in) is enough to transfer not only the 590 Newton meters (435 lb-ft) of torque, but even a maximum of more than 1000 Nm (735 lb-ft). The Porsche 911Turbo, with 560 Nm (415 lb-ft) of torque, and the even heftier GT2, with 620 Nm (472 lb-ft), employ clutch plates of 240 mm (11.5 in) in diameter.
The size differences are a matter of principle. Porsches of the 911 production series, all the way up to the Turbo, use a conventional single-disc clutch with a dual-mass flywheel and a driven disc of heavy steel. The Carrera GT, on the other hand, harbors racing technology harnessed for the road. Here, two disks, not one, ensures the transfer of forces. And for the first time in an automobile, these friction plates, following the example of their counterparts in the braking system, are made of a ceramic. The good experience with the Porsche Ceramic Composite Brake (PCCB) has led to development of the Porsche Ceramic Composite Clutch (PCCC), which also is produced in cooperation with SGL Brakes GmbH, located in Meitingen.
The modern variant of this material surpasses steel in three major qualities: This kind of ceramic is lighter, harder, and more heat-resistant than metal. Top-quality material also covers the backing plates of the organic sinter shoes by the company Pagid: Titanium won out here over heavier steel and weaker aluminum.
The weight reduction over the 7.6 kilogram (16.75 lb) conventional clutch of a 911 Turbo is more than fifty percent for the 3.5 kilogram (7.7 lb) PCCC. The diet has its price. Bernd Ramler, drivetrain project manager for the Porsche Carrera GT, admits: “Because of the small batches, we still have to figure on a factor of ten in pricing, but we can see a potential for lower prices in the future.”
Even then, building a ceramic clutch will still be a high-effort process. Its friction plates have to face even higher challenges than do the ceramic brake discs. While the carbon-fiber component of brake discs still consists of short, non-oriented fibers—“sauerkraut” in workshop jargon—the clutch, exposed to bending and centrifugal forces, needs carbon fibers in the more robust form of a fabric.
In the first production stage, the fabric is pressed into a plate, at a temperature of 100 degrees C (212°F). Then the plate with the carbon fiber mat and epoxy resin is placed into a hotter oven, and baked at more than 700 degrees C (1200°F). After this process, the brake and clutch plates already have the extreme strength of the carbon fiber material as it is used for the brake discs of Formula One cars. But the final long-lasting strength needed for road operation only comes with the so-called “silicization” process, in which the carbon-fiber plates get a coating of liquefied quartz sand during a third baking. This enrichment with silicon takes place at 1700 degrees C (3000°F), in an extremely powerful vacuum. At this temperature, the melted sand is more fluid than water, and the silicon displaces the resin from the carbon fiber structure and occupies seventy percent of the volume of the saturated plate.
Thus, a new substance, silicon carbide, arises from the embers, a hardship case that engineers value highly. With a hardness of 9.7, silicon carbide is right behind diamonds, which define the “absolute-hardness” score of 10. The material’s tough resistance against wear and high temperatures also thwarts tools; working the surface requires diamonds.
Insight: The diameter of the clutch plates of the Carrera GT is only 169 millimeters...
The effort that goes into the ceramic clutch at the Carrera GT results in durability far beyond that of a conventional clutch. That is especially impressive for a clutch subjected to considerable torque. The low weight and small dimensions of the PCCC reinforce the dynamic qualities of the super sports car.
Such materials not only help reduce the rotational masses of the clutch by a factor of ten, but offer less wear than conventional material. Combined with a lightweight flywheel, rotational mass of the engine is exceptionally light.
Because of its small firing interval, the race-bred ten-cylinder racing engine holds stable in neutral at low inertia. There, the small and light clutch is just the right thing to successfully support, with minimal mass, this machine’s talent to rev up very quickly. Lightning reactions to the commands of the accelerator are a correct and sporting answer to this physical fitness program. At the same time, the Carrera GT demands a deft touch on the accelerator and the clutch from the driver. A smooth start requires a well-measured pinch of throttle and sensitive handling of the clutch, which conveys full power over a short take-up path.
Another highlight of this clutch is its short diameter of only 6.5 inches (165 mm). At such a height, the transmission and engine are very short and mounted low in the chassis.
The smaller dimensions of the clutch have made profound changes possible in the design of the power transmission, and have thus promoted its ultra-sporty character. In an engine that, thanks to dry-sump lubrication, has no oil pan extending toward the ground, the size of the clutch housing determines the ground clearance and therefore also affects the installation position of the engine. So the smaller the clutch and the shorter the distance between the middle of the crank-shaft bearings and the underside of the engine case (98.5 millimeters / 3.9 inches) in the Carrera GT), the lower the engine can be installed and the further the center of gravity ultimately drops.
Just how low? Well the crankshaft rotates just 4.0 inches (102 mm) from the floor and the transmission actually sits lower than the rear differential.
That the engine in the Carrera GT is as low as in a racing car wasn’t enough for Ramler, however. It was also important to him to move the mass of the mechanical structure as close as possible to the middle of the vehicle and to its center of gravity. The six-speed transmission of the Carrera GT from the gear factory in Hör in Weiden groups its shafts transversely and at the level of the differential, with no overhang. “Because if we were to pack a 65-kilogram (145 lb.) transmission behind the rear axle of such a car,” Ramler explains, “it would be as wrong for the balance of handling characteristics as if the tail were to wag the dog.”
PORSCHE CARRERA GT: 6-Speed with a Ceramic Clutch
Technical Information:
The Porsche Ceramic Composite Clutch (PCCC) of the Porsche Carrera GT:
- Two-plate dry clutch
- Hardness of the silicon carbide: 9.7 (absolute hardness: 10)
- Diameter of the clutch plates: 169 millimeters
- Power transmission: max. > 1000 Nm (735 lb-ft)
- Engine run-out speed:over 20,000 rpm
- Weight: 3.5 kg (7.7 lb)
Porsche-Carrera-GT_Clutch-Technology
Porsche-Carrera-GT_Making-of-video