In 1981 Porsche started work on a prototype racer to suit the new Group C regulations. It was the first all new racer Porsche constructed in over a decade and was quite a departure from the 936, which shared many components with Porsche's prototypes of the late 1960s.
The only proven part of the new '956' was the aluminum flat 6 engine, which had powered the 936.
For many years Porsche had relied on a triangular spaceframe structure for their products, but to keep up with the competition a completely new aluminum monocoque chassis was designed for the 956. The monocoque supported the front suspension and a rear subframe. The engine and rear suspension were mounted on the subframe. Suspension was by wishbones all-round with the rear coil-spring / shock absorber unit mounted on top of the gearbox to keep them out of the airflow.
The regulations stated that the section of the bottom right behind the front suspension was completely flat, to prevent that the cars would have extreme ground effects bottoms. Porsche fitted the 956 with large venturis, starting right behind the mandatory flat section, making it the first the ground-effects Porsche. Because of its width, a flat engine is not ideally suited for ground-effects, but this was somewhat fixed by tilting the engine upwards. Combining the ground-effects bottom with a simple but effective body, the 956 generated over 3 times more downforce than the 917.
To suit the fuel economy regulations best, the engine management of the already efficient flat 6 engine was revised with the help of Bosch. The mechanical fuel injection system was replaced by a digital unit, resulting in a similar output as the 936 engine, but with better fuel efficiency and more torque. Bolted onto the engine was a new five speed gearbox with a syncromesh on all gears. It replaced the sturdy four speed unit used on the 936, which was originally designed for the hugely powerful CanAm cars.
After nine months of hard work, the 956 made its debut, two races into the season. Its main competition consisted of underfinanced or badly supported cars from Lola and Ford. At its debut in the Silverstone Six Hours race, the 956 finished second overall behind an old Group 6 Lancia and first in the Group C class. A sign of things to come! In the following four years, the Porsche 956 dominated international sportscar racing and secured four consecutive LeMans 24 Hours victory. The only factory team taking Porsche on was Lancia, but they never seemed to get the reliability right. In qualification sessions, the Lancias often proved their pace, but they rarely managed to finish a race. In the three years the Lancia works team took part in the championship, they managed to beat the 956 only once. Key to the success of the 956 was the large fleet of customer entered example, backing up the works entries. A total of 10 works and 17 customer cars were constructed.