Porsche 959

The Porsche 959 is a sports car manufactured by German automobile manufacturer Porsche from 1986 to 1993, first as a Group B rally car and later as a road legal production car designed to satisfy FIA homologation regulations requiring at least 200 units be produced.

The twin-turbocharged 959 was the world's fastest street-legal production car when introduced, achieving a top speed of 317 km/h (197 mph), with some variants even capable of achieving 339 km/h (211 mph). Combining race-car performance with luxury-sedan comfort and everyday drivability in dry, wet and snowy conditions, it was considered the most technologically advanced road car of its time.

After the successful introduction of all-wheel drive on more rally-specific cars like the Audi Quattro, it was one of the first pure high-performance sports-cars with all-wheel drive, providing the basis for Porsche's first all-wheel drive 911 Carrera 4 model. Its performance convinced Porsche executives to make all-wheel drive standard on all turbocharged versions of the 911 starting with the 993. The twin-turbo system used on the 959 also made its way to future turbocharged Porsche sports cars. In 2004, Sports Car International named the 959 number one on its list of Top Sports Cars of the 1980s.

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 rallying 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 four 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 (2.8 L). It was coupled to a unique manual transmission offering six forward speeds with the first gear labelled "gelände" (terrain), allowing the car to pass noise regulations, 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 relatively compact power unit. 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.