Lightweight Showcase - Porsche AG's 911 is the industry's single most recognizable sports-car nameplate. Yet when it comes to sheer desirability, Porsche always seems to finish second to its Italian rival Ferrari SpA



Porsche AG's 911 is the industry's single most recognizable sports-car nameplate. Yet when it comes to sheer desirability, Porsche always seems to finish second to its Italian rival Ferrari SpA.

That's largely because Porsche prides itself on making an "everyday" type of high-performance sports car, one not so high-strung - or high-priced - that you couldn't let your neighbor take it for a spin around the block. Ferrari makes supercars.

Not that Porsche hasn't played that game. In 1988, it made the 959, a rare, all-wheel-drive, mega-turbocharged rocket. But it proved only a brief dalliance, as Porsche continued to focus on the business of adapting to a changing industry climate and Ferrari kept on making supercars.

Now, though, Porsche has no choice. Supercars are popping up everywhere, and the Stuttgarters feel their honor is at stake as Bugatti, Mercedes-Benz and even Ford Motor Co. are putting the final touches on their own supercars. So Porsche rolled up its sleeves, bored out a snarly all-aluminum V-10 originally developed for Le Mans racing, and told its advanced-materials engineers to prepare for some overtime.

Because if you're to develop a modern-day supercar, it must be a materials showcase - it's the only way to set yourself apart these days. Everything's fast.

Porsche's new Carrera GT, which the company says will launch to 62 mph (100 km/h) in 3.9 seconds and top out at about 205 mph (330 km/h), will cost $440,000 when any of about 500 U.S. customers get their hands on one this fall.

Like the new Ferrari Enzo, the Carrera GT's main calling card is carbon fiber, but the car employs liberal doses of titanium, magnesium, aluminum - even a special new type of stainless steel.

The Carrera GT's most impressive components all use various forms of carbon-fiber composites. The monocoque, or passenger-enveloping "tub" that includes the windshield header and integral rollover bars - is one enormous carbon-fiber plastic (CFP) form that looks for all the world like those photos you may have seen of bare jet-fighter cockpits. The engine/transmission carrier, another hulking monopiece subframe of CFP, bolts to the monocoque.

The CFP material also is used for the door "skins," closure panels and floorpan. Porsche says the bare chassis weighs just 220 lbs. (100 kg). The CFP production process sees skilled technicians laying intricate layers of carbon-fiber "tissue" in patterns and thicknesses specific to the load-bearing requirements of the area being "built up."

The tissue is impregnated with resin, and there may be a layer of aluminum or plastic honeycomb sandwiched inside the CFP. This complicated form is sealed with an airtight foil and inserted in an autoclave that is pressurized to between 87-116 psi (6-8 bar), where everything bakes together to form the light but immensely stiff CFP final product.

All of the carbon-fiber craftwork, incidentally, is not a Porsche undertaking. Suppliers, whose identities are guarded by Porsche sources, perform all of the chassis "lay up" and produce the other carbon-fiber components.

High on the "wow factor" list is the Carrera GT's carbon-fiber clutch, which Porsche claims as a world first and is "absolutely uncharted technical territory." Although this, too, is borrowed from the racing world, Porsche engineers point out one major difference. Carbon-fiber racing clutches have a rather brief service life: exactly one race.

The Porsche Ceramic Composite Clutch (PCCC) for the Carrera GT uses two clutch plates made of carbon-ceramic composite and silicon carbide and enables engineers to specify a diameter of just 6.7 ins. (169 mm) - the clutch for the production 911 Turbo is 9.4 ins. (240 mm) - and the complete assembly weighs 7.7 lbs. (3.5 kg), half the mass of the conventional 911 clutch assembly.

The PCCC's compact size made it possible for engineers to keep the powertrain mass as low as possible and reduces rotational mass. Any doubts about durability should be assuaged by Porsche's bench-test claim of 738 lb.-ft. (1,000 Nm) torque capacity, a 20,000 rpm burst speed and 16,000 simulated starts.

The Carrera GT also sports Porsche's Carbon Ceramic Brakes (PCCB). Porsche already has fitted the PCCB system (engineered by Italian brake specialist Brembo SpA) on various production 911s.

Still, the claims for PCCB border on phenomenal: The material is 35 times harder than steel, can handle temperatures of 2,550 degrees F (1,400 degrees C), are all but fade-resistant and weigh half that of a conventional cast-iron disc. Never mind each PCCB disc takes a week to make.

Also intriguing is the use of austenitic stainless steel (H400) in the front and rear sidemember crash absorbers, the suspension pushrods and lower rear-axle wishbones. Porsche engineers claim the H400 stainless presents higher strength at lower weight than more-conventional stainless and a superior strength-to-formability ratio.

Porsche hands out no body stiffness numbers and is mum about the car's center of gravity height, saying only that it was a design priority. One engineer allows the car's center of gravity height is "significantly lower than the (current) 911."

As proven by the carbon-ceramic brakes, working with carbon fiber - particularly when taken to such extremes as in the Carrera GT - is time-consuming. Porsche expects to lavish three weeks or more on each example, and wrecking one wouldn't be a good idea: A Porsche materials engineer says cars in need of severe repair might have to be returned to the factory.

Other lightweighting tidbits:

*The Carrera GT's 19-in. front and 20-in. rear wheels are forged magnesium and 25% lighter than aluminum. There are no lug nuts: The wheels are held on by a single central "bolt" of aluminum, red for the left side, blue for the right.

*The seat shells are carbon fiber, and each is a feathery 23.5 lbs. (10.7 kg).

*The twin removable roof panels - carbon fiber - each weigh 5.3 lbs. (2.4 kg).

*The Carrera GT's 5.7L DOHC V-10 weighs 472 lbs. (214 kg), thanks to all-aluminum construction and Nikasil cylinder coating in place of heavy iron liners. It produces 612 hp at 8,000 rpm and 435 lb.-ft. (589 Nm) of torque at 5,750 rpm; specific output is 107 hp/L.

Carrera GT's overall weight of 3,043 lbs. (1,380 kg) does not appear outlandishly light; a Chevrolet Corvette convertible - a 2-seat roadster of similar proportions - weighs 3,248 lbs. (1,456 kg).

But the Carrera GT and other new-age supercars simply may be reworking the old hot-rodders' mantra that summarized the cost of adding incremental amounts of power: "Speed is money. How fast can you afford to go?"

Now it's, "Losing weight costs money. How light can you afford to be?"
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