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This was the fourth version of the 991 RSR - the first two came with the rear engine, then the first mid-engine version was launched (all 4.0-litre) and finally the mid-engined RSR 4.2 with the largest 911 engine ever made. The increase in the engine capacity is a question mark as on production models the capacities are decreased and turbochargers are used. The 991 RSR 4.2 didn't have anything in common with the production cars anymore. No change in terms of power-to-weight ratio.
Porsche 911 GT America (991)
The 911 GT America was based on the 991 GT3 Cup. It was built exclusively for the United Sports Car Racing (USRC) series and its GT Daytona class for 2014. While the GT3 Cup had a 3.8-litre engine at the time, the GT America was fitted with a 4.0-litre unit developing 351 kW. The main visual difference is the rear spoiler made to fit the USRC rules. Like the GT3 Cup, the GT America has 380 mm steel brake rotors at the front axle with 6-piston fixed calipers.
The 935 tribute car was a non-street-legal collector's car built in a series of 77 cars. It was built from the 911 991.2 GT3 R racing car, fitted with the engine and transmission from the 911 991.2 GT2 RS street car and with the bodykit showing some design details from the 935 cars. The problem: it was not as powerful as the 1978 935 was with even smaller engine and the modern car is much heavier, so the power-to-weight ratio was almost 60% better 40 years earlier.
Based on the 911 GT3 RS production sports car, Porsche has designed a customer sport race car for GT3 series around the world: The 911 GT3 R. In developing the more than 368 kW (500 hp) racing nine-eleven, special attention was paid to lightweight design, better aerodynamic efficiency, reducing consumption, improved handling and optimised safety. The 911 GT3 R features the distinctive double-bubble roof, and the wheelbase which had been lengthened compared to the prior generation.
As the rules do not permit higher output engines, the engine for the 991 RSR was taken from the 997 GT3 RSR 4.0 and the development work focused on the chassis, body, aerodynamics and the gearbox. A wishbone front suspension replaced the McPherson struts used in 997. A new development was the lightweight gearbox. One of the priorities in the development was the more evenly balanced weight distribution. The centre of gravity was lower, too.
Porsche will only build 30 examples of the Clubsport 25. Mechanically, it's similar to the regular GT2 RS Clubsport. It makes the 691 horsepower from a twin-turbocharged 3.8-liter flat-six. But it gets many, many changes to the exterior and even the cooling system. As you can clearly see, the body has been lengthened, and it has also been widened. The latter is necessary to house the wide, low-offset 18-inch wheels taken from the Porsche 935, though without the aerodynamic covers.
Two decades after the different 911 GT1 cars the mid-engined 911 is back! In order to install a proper diffuser under the rear end of the 991, the engine had to make room for it and the engine/transmission unit was rotated 180 degrees. The extended rear diffuser, a top-suspended rear wing and the new side mirrors help to increase downforce with reduced drag. The FIA rules meant no turbo was needed due to power limits, so the normally aspirated 4-litre flat-6 was taken from the 991 GT3 R.
The rear of the world’s most-produced GT racing car now houses a 4-litre, six-cylinder flat engine for even more drive. Thanks to thoroughbred motorsport technology, the compact engine with direct fuel injection delivers peak performance of 357 kW (485 hp). A range of innovative details also improve efficiency in addition to engine performance, ensuring even better durability of the naturally aspirated engine in racing mode and reduced maintenance costs.
The new Porsche 911 GT3 Cup is powered by a 3.8-litre six-cylinder flat engine. It generates 460 hp (338 kW) at 7,500 revs, surpassing the predecessor by 10 hp. A six-speed dog-type gearbox developed by Porsche Motorsport which is operated via shift paddles at the steering wheel for the first time in a Porsche brand trophy race car transmits the power to the rear axle. The single piece race wheels with centre mount were also new.
The GT3 R has always been placed between the GT3 Cup and the very expensive RSR. All the 991.2 racing cars have normally aspirated 4-litre engines. Compared to the 991.1 GT3 R, the 991.2 GT3 R engine offers a broader usable rev range and the engine response is more precise due to 6 throttle butterflies. The roof, front hood and fairing, wheel arches, doors, side and tail sections, rear lid and interior trim are made of carbon-fibre reinforced plastic. Gets new double wishbone suspension.
This car was officially called as the 911 GT2 RS Clubsport, but the name is rather misleading. The car was not built for the GT2 racing class which is long extinct and club sport has stood for Porsche club track days while this non-streel-legal car is a real racing car. Finally, the car was based on the 991 GT2 RS, which already had the Clubsport version. So, in order to understand what is what, we call it "991 GT2 RS Clubsport racing version". The 991 GT2 RS engine with 515 kW was powerful enough, so it was not tuned.