Porsche 959 Group B Prototype 1983

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Porsche 959 Prototyp

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Development history and overview
Development of the 959 (originally called the Gruppe B) started in 1981, shortly after the company's then-new Managing Director, Peter Schutz, took his office. Porsche's chief engineer at the time, Helmuth Bott, approached Schutz with some ideas about the Porsche 911, or more aptly, a new one. Bott knew that the company needed a sports car that they could continue to rely on for years to come and that could be developed as time went on. Curious as to how much they could do with the rear-engined 911, Bott convinced Schutz that development tests should take place, and even proposed researching a new all wheel drive system. Schutz agreed, and gave the project the green light. Bott also knew through experience that a racing program usually helped to accelerate the development of new models. Seeing Group B rally racing as the perfect arena to test the new development mule and its all wheel drive system, Bott again went to Schutz and got the approval to develop a car, based on his development mule, for competition in Group B.

The powerplant is a sequential twin-turbocharged DOHC flat-six engine equipped with 4 valves per cylinder, fuel fed by Bosch Motronic 2.1 fuel injection with air-cooled cylinders and water-cooled heads, with a bore x stroke of 95 mm × 67 mm (3.74 in × 2.64 in) for a total displacement of 2,849 cc (173.9 cu in). It was coupled to a unique manual transmission offering five forward speeds plus a "gelände" (terrain) off-road gear, as well as reverse. The engine was largely based on the 4-camshaft 24-valve powerplant used in the Porsche 956 and 962 race cars. These components allowed Porsche to extract 450 PS (331 kW; 444 hp) at 6,500 rpm and 500 N⋅m (369 lb⋅ft) of torque at 5,000 rpm from the compact and efficient power unit.[7] The use of sequential twin turbochargers rather than the more usual identical turbochargers for each of the two cylinder banks allowed for smooth delivery of power across the engine speed band, in contrast to the abrupt on-off power characteristic that distinguished Porsche's other turbocharged engines of the period. The engine was used virtually unchanged in the 959 road car as well.

To create a rugged, lightweight shell, Porsche adopted an aluminium and Aramid (Kevlar) composite for the body panels and chassis construction along with a Nomex floor, instead of the steel floor normally used on their production cars. Porsche also developed the car's aerodynamics, which were designed to increase stability, as was the automatic ride-height adjustment that became available on the road car (961 race cars had a fixed suspension system). Its drag coefficient was as low as 0.31 and aerodynamic lift was eliminated.

The 959 also featured Porsche-Steuer Kupplung (PSK) all-wheel-drive system. Capable of dynamically changing the torque distribution between the rear and front wheels in both normal and slip conditions, the PSK system gave the 959 the adaptability it needed both as a race car and as a "super" street car. Under hard acceleration, PSK could send as much as 80% of the available power to the rear wheels, helping make the most of the rear-traction bias that occurs at such times. It could also vary the power bias depending on road surface and grip changes, helping maintain traction at all times. The dashboard featured gauges displaying the amount of rear differential slip as well as transmitted power to the front axle. The magnesium alloy wheels were unique, being hollow inside to form a sealed chamber contiguous with the tyre and equipped with a built-in tyre pressure monitoring system.

The 959 was actually produced at Karosserie Baur, not at the Porsche factory in Zuffenhausen, on an assembly line with Porsche inspectors overseeing the finished bodies. Most of Porsche's special order interior leather work was also done by the workers at Baur.

The 1983 Frankfurt Motor Show was chosen for the unveiling of the Porsche Group B prototype. Even in the closing hours of October 9, finishing touches were being applied to the car to go on display the next morning. After the first two prototypes, the bodywork was modified to include air vents in the front and rear wheel housings, as well as intake holes behind the doors. The first prototype receiving those modifications was code named "F3", and was destroyed in the first crash test.

Source: Wikipedia