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A History of the Porsche Carrera GT
Porsche Carrera GT

Introduction to the Porsche Carrera GT

The Porsche Carrera GT is known to many as the current Porsche supercar representing the latest and best standards of sportscar technology available in the automotive industry. Only a few know about his origins though: The development of the Carrera GT may be traced back to its predecessors, the 911 GT1 and LMP1-98 Porsche racing cars of which both designs ended in 1998 due to the FIA and ACO rule changes. As a result Porsche planned on a new Le Mans prototype for 1999. The car was originally intended to be powered by a turbocharged flat-6, but was later redesigned to use a new normally aspirated V10 engine, pushing the project back to planned competition in 2000. The V10 was a unit originally secretly built by Porsche for the Footwork F1 team in 1992, but later shelved. The engine was resurrected for the Le Mans prototype and the displacement upgraded to a size of 5.5 litres. Unfortunately the race car project was cancelled after two days of testing of the first car in mid-1999, mostly due to Porsche’s wish to build the Cayenne with involvement from Volkswagen and Audi, thus requiring engineering expertise and financial resources to be pulled from the motorsports division. It was also speculated that VW-Audi chairman Ferdinand Piëch wanted Audi’s new Le Mans Prototype, the Audi R8 not to face competition from Porsche in 2000. That meant the end of a Le Mans race car project was at the mean time the beginning of a street legal supercar project though:

Porsche did keep part of the project alive by presenting the 5.5 V10 from the prototype mounted in a mid-engined concept car shown at the 2000 Geneva Motor Show. This concept car was mainly an attempt to draw attention to their display, nobody was considering a serial production of the car at the time being. Surprising interest in the vehicle and an influx of revenue provided from the Cayenne helped Porsche (who was still recovering from the losses of the nineties) decide to produce the car, and development started on a street legal version that would be produced in small numbers at Porsche’s new manufacturing facility in Leipzig.

The Carrera GT was a totally new development leading to a cross-breed between a race car and street legal supercar incorporating the latest know-how of the world famous Weissach Motorsport Centre. Porsche describes the Carrera GT as “the street legal sportscar which is the closest to the racetrack” they have ever built. It is uncompromisingly and puristicly focusing on performance. Every last component in each area of the car has been custom-engineered for optimum performance. The use of costly state-of-the-art materials combine major weight savings with intense structural rigidity to achieve exceptional performance and handling characteristics while still offering exemplary safety reserves. Besides these requirements Porsche also concentrated on an as low-as-possible centre of gravity and even weight distribution.

In order to meet with the lightweight and structural requirements, Porsche designed the main chassis structure as a monocoque made from aerospace-grade composites, including carbon-fibre sandwich construction with a high-strength honeycomb core. Carbon fibre was also used wide lavishly over all areas of the car. Porsche decided to mount the V10 as deep as possible in the chassis create an extremely low centre of gravity which required the development of a new clutch system with a minimum diameter in order to still keep sufficient ground clearance. In order to comply with the requirement of an even weight distribution leading to a balanced handling, the engineers placed the engine and aluminium fuel tank directly behind the cockpit.

According to Porsche, the development of the Carrera resulted in over 75 technology patents that have been filed.

Engine and transmission

We already referred to the history of the V10 heart of the Carrera GT above. So let us focus more on the technical details. The powerplant is a normally aspirated 68-degree V 10 featuring four-valve heads equipped with sodium-cooled exhaust valves. A 98 mm bore is combined with a 76 mm stroke resulting in a total displacement of 5.7 litres. Maximum power is 605 bhp @ 8,000 rpm and 590Nm @ 5750rpm resulting in an exceptional specific output of 105.5 hp (SAE) per litre.

Each bank of cylinders is equipped with an independent intake twin-manifold system and exhaust system featuring primary and main catalytic converters. The twin-flow manifold system supplies a separate flow of air to each of the cylinder banks. To do that, the manifold is equipped with two separate throttle tracts as well as separate air filters with Helmholtz resonators. The resulting vibration of the incoming air is one of the key ingredients in the characteristic sound of the Carrera GT.

To minimise vibration and negative noise, the engine is located using a three-point system of flexible mounts within a specially developed carbon-fibre structure. The compact crankcase sections are cast in a selection of lightweight alloys offering optimum mechanical strength and thermal stability.

Weight saving initiatives also affected the design of the engine, virtually all water and oil channels form an integral part of the lightweight cast-alloy block. As a result, Porsche engineers dispensed with the usual array of joints and seals typically found on modern engines. The engine is cooled using a cross-flow system in which each individual cylinder receives the optimum supply of coolant at all times. With each cylinder receiving an even supply, the system helps maintain a balanced temperature throughout every part of the engine. The Carrera GT radiator is about five times the size of a 911 turbo’s.

Inside each cylinder, the Nikasil-coated bore helps minimise friction losses while extending the life of the engine. At the base of the engine, the crankshaft assembly has been specially optimized to facilitate a maximum engine speed of 8,400 rpm: The engine features a special forged crankshaft offering exceptional torsional rigidity. The inertia forces acting on the crankshaft have been considerably reduced through a combination of titanium connecting rods and three-ring aluminium pistons (extremely low weight). The result is a smoother and more balanced delivery, even at very high rpm. Additionally, a lightweight harmonic balancer helps eliminate torsional vibration to ensure more accurate valve train control while the camshafts are driven by a chain and gear system minimizing engine noise. Each intake camshaft is equipped with VarioCam technology, a patented Porsche system that uses a rotary adjuster to offer continuous modulation of the camshaft phase angle over a range of 40 degrees.

Engine Oil is circulated through a series of ten pumps, nine of which ‘scavenge’ the oil back from the engine. This ‘dry sump’ configuration ensures a permanent and consistent lubrication, even under the extreme lateral loads that are encountered in the Carrera GT. The external oil reservoir is incorporated into the gearbox casing, where it uses an integrated air separator to de-foam the oil. A dedicated oil cooler was also implemented to help limit engine temperatures.

With its ‘V’ configuration and low position, the new V10 is a key factor for the car’s ultra-low centre of gravity and with its impressively light weight of 205 kg only also considerably contributing to the weight saving programme. Together, this array of racing technologies represents one of the most uncompromising engines ever developed for the road.

The Carrera GT features a traditional six-speed manual transmission. Much more innovative is the clutch system that has been specially developed for the Carrera GT. The main requirements for this two-plate ceramic dry clutch (Porsche Ceramic Composite Clutch; PCCC) were to minimize its diameter to allow the engine to be positioned as low as possible (The crank is positioned only 98.5mm from the floor of the chassis) for an as low-as-possible Centre of Gravity and to be as light as possible for a minimum rotating mass.

The Carrera GT is the world’s first car fitted with an extremely compact double-disc dry clutch with ceramic discs – a joint development by Porsche and ZF Sachs. It’s components had be extremely compact, light-weight and yet able to hold up to high loads which basically meant engineers had to square the circle. In the past, such compact dimensions could only be achieved by using carbon clutch discs. However, this material used in racing cars is not suitable for production vehicles since its maximum lifetime of 15,000 kilometres does not meet the requirements typically encountered in normal, everyday driving. Porsche engineers found the answer to this problem: both discs of the PCCC (Porsche Ceramic Composite Clutch) fitted at ZF Sachs Race Engineering are made of ceramics and therewith are lightweight and durable at the same time. The result is impressive: The clutch combines an extremely low weight of merely 3.8 kilograms (For comparison: the clutch installed in a volume car weighs approximately 10-12 kilograms) and a diameter of 192 mm / length of 58 mm with heavy duty performance slip resistant transmitting the 590Nm of the powerplant.

Bodywork

The Carrera GT’s main chassis structure – consisting of monocoque, windscreen surround and supplemental safety system – is made from carbon-fibre composites with a honeycomb core, a technology which is currently used in Formula One and Aerospace offering exceptional flexural and torsional strength at an absolute minimum weight.

The rear of the monocoque is a highly robust yet lightweight carbon-fibre structure which supports the engine and gearbox unit. This structure – known as the engine carrier – is bolted to the monocoque combined with which it forms the main stressed members on the car. This combined chassis is extremely light, yet considerably stronger than the pressed metal shell on a conventional car. The carbon fiber monocoque and subframe were produced and assembled by ATR Composites Group of Italy.

As the main structural members, the monocoque and engine carrier provide the mounting points for the suspension as well as the underlying structure for the external bodywork and cockpit assemblies. They are also designed to absorb impact energy in the event of a crash from the front and rear deformation zones. As the name implies, the engine carrier structure supports the entire powertrain assembly. Specially developed and patented by Porsche, this unique combination of monocoque and engine carrier offers a level of structural integrity that is not only exceptional on an open-top car, but also on a par with dedicated competition vehicles.

The fuel tank is located directly behind the cockpit, where it both consolidates the dynamics of the car (concentration of mass close to the centre of gravity) and allows an optimum balancing of the car and prevents gradual changes in individual wheel loads as the 92 litres of fuel are consumed.

The external bodywork on the Carrera GT is bolted to the underlying chassis structure, in contrast to a conventional road car, the external panels are completely unstressed and have a primarily aerodynamic and aesthetic and therewith no structural function.

The bodywork of the Carrera GT was mainly designed to follow its. The Carrera GT features an open-top two-seater layout with a two-piece detachable hardtop in carbon fibre. It includes an automated rear wing spoiler which automatically deploys above 110 km/h (70 mph) and large side inlets and air dams that help cool the large V10 framed by the carbon fibre rear hood. The rear wing has been designed in close conjunction with the underbody panelling with rear diffuser using ground-effect for improved aerodynamic down force. The bodywork is completed with frameless doors in carbon fibre with integrated side-impact protection, front and rear lids, rear side panels and sill panels in carbon fibre and front and rear aprons in plastic.

The Carrera GT has a basic five colour paint scheme which includes Guards Red, Fayence Yellow, Basalt Black, GT Silver and Seal Grey. Custom colours were also available from the factory.

Suspension, Brakes and wheels

Front and rear suspension consists of racing double wishbones with inboard spring-and-damper units.

The Carrera GT features the Porsche Ceramic Composite Brake (PCCB) which consists of a lightweight ceramic disc with involute cooling channels and a specially developed composite pad. Each of the front and rear discs have a diameter of 380 mm. They are cross-drilled and internally vented for optimum dispersal of moisture and heat and offer an approximate 50% weight saving over conventional metal equivalents. Since all of that weight is entirely ‘unsprung’ – i.e., not supported by the car's suspension – the PCCB system delivers immediate benefits in terms of handling, agility and – last but not least – also fuel economy.

Each disc is gripped by a powerful six-piston calliper. This setup leads to a breathtaking deceleration as well as unparalleled consistency and consistently high friction levels across a wide range of operating temperatures. Also, inherent fade resistance makes for safer deceleration from even the highest speeds, while the system’s prodigious response requires only moderate pedal inputs from the driver.

Another key benefit of the PCCB system is the remarkable durability of both pads and discs. Thanks to the exceptional surface hardness of the ceramic disc, the rate of wear is remarkably low compared with conventional braking systems.

The Carrera GT features dedicated five-spoke wheels incorporating the latest technology standards. Measuring 19 inches at the front and a full 20 inches at the rear, these ultra-lightweight wheels are made from forged magnesium, a material which represents a major step forward in reducing unsprung weight. By limiting wheel momentum as the suspension compresses and rebounds, lower unsprung weight allows to maintain improved contact between road and tyre and thus maximise traction under acceleration, cornering and braking. Another important benefit is the added structural density – and therefore durability – that is imparted by the forging process.

The Carrera GT wheels are mounted using a centre-lock system with a single multi-point nut. Left-hand wheel nuts have a right-hand thread, while those on the right have a left-hand thread ensuring that the thread on each nut runs contrary to the primary direction of travel on all four wheels so that the rotation of each wheel tends to tighten the nut, rather than working it loose. This race-derived solution is combined with a high-strength hub and large-format bearings to achieve a more accurate wheel location.

The wheels are equipped with high-speed Michelin tyres specially developed for the Carrera GT with an extremely generous rolling circumference measuring 265/35 ZR 19 at the front and 335/30 ZR 20 at the rear. Compound and tread are specially designed to ensure shorter braking distances and consistent handling, particularly in wet conditions. All four tyres are equipped with an integrated tyre-pressure monitoring system (TPMS) which issues an automated warning in the event of any drop in pressure.

Performance

The Carrera GT’s performance is the result of its uncompromising conception and design. The performance numbers don’t do the supercar enough justice but are already very impressive: Top speed is 330 km/h (205 mph), 0-100km/h sprint time (0-62mph) is 3.9 sec and 0-200km/h ( 0-124 mph) takes 9.9 secs only. The Carrera GT does the quarter mile in 11.4 secs. Also the decelaration performance is astonishing, the Carrera GT comes from 100km/h to a standstill in 33.3m only.

It achieved a lap time of 7:32,44 at the infamous Nürburgring Nordschleife.

Production numbers

Originally a production run of 1,500 cars was planned. Porsche changed these plans in August 2005 when the decision was made that it would not continue production of the Carrera GT through 2006, citing discontinuation was due to changing airbag regulations in the US. As of May 6, 2006, 1,270 GT’s had been manufactured, with 604 being sold in the United States.

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