Built to comply with the championship's new
Group C regulations which were introduced in 1982, the car was a replacement for Porsche's successful
936 model which competed in the previous
Group 6 category of the World Championship. The project began in June 1981, and the first prototype chassis was completed on March 27, 1982, in time for the beginning of the World Championship season.
Jürgen Barth tested the first chassis at Porsche's private test track. The 956 features a chassis made of an
aluminium monocoque, a first for the company, helping to allow the car to meet the weight minimum in Group C. The engine is the same as the one used in the
Porsche 936/81, the Type-935 2.65 L turbocharged
Flat-6, producing approximately (originally developed as an Indycar engine; hence the cubic capacity used). An improved chassis with better
fuel efficiency from a
Bosch Motronic electric system was developed for 1984, being termed the
956B. In total, twenty-eight 956s would be built by Porsche from 1982 to 1984, with an unofficial 29th chassis built from spare parts by Richard Lloyd Racing. The 956 was also the first Porsche to have
ground effect aerodynamics. As a comparison, the ground effects Porsche 956 produced over three times as much downforce as the older model
Porsche 917 that raced over a decade earlier. In 1983, 956 chassis #107 was used by Porsche as a testbed for their P01
Formula One engine, later badged as
TAG and used exclusively by
McLaren. The car was able to test some of the characteristics of a Formula One car in order to develop the engine. The engine became highly successful in F1, and while never the most powerful on the grid, between 1984 and 1987, the turbocharged TAG-Porsche would win 25 Grands Prix and help McLaren to two Constructors and three World Driver's Championships. As of the
2012 German Grand Prix, the TAG-Porsche engine sits in 7th place on the list of F1 race winning engines. Porsche tested its Porsche Doppelkupplungsgetriebe (PDK)
dual-clutch transmission in the 956 in the early 1980s. PDK would be used in the
Porsche 962, and would eventually make its way into production Porsches with the 2009 997 Carrera and Carrera S. The Porsche 956 also appeared with two different rear wing designs. The cars were fitted with a larger, high downforce rear wing for most events. For the
Circuit de la Sarthe at
Le Mans however where top speed on the almost long Mulsanne Straight was essential, the 956 was fitted with a much lower and smaller 'low drag' wing to enable the cars to reach speeds of around . Some of the privateer teams would also experiment with a front wing attached to the cars at the tighter circuits in an effort to increase front downforce, but wind tunnel testing eventually found that these wings were disrupting the airflow over the car and actually increased the aerodynamic drag making the cars slower in a straight line. Notably, the factory backed
Rothmans Porsche team did not make use of the smaller front wings. Many attributed this to the fact that the Rothmans cars used a one piece body undertray which helped increase the downforce generated by the ground effect aerodynamics while the customer 956's used a twin undertray which disrupted the air flow and slightly decreased the downforce. The 956 would be officially replaced by the
Porsche 962 in 1985, an evolution in the 956's design. ==Racing history==