Porsche 961 - Development

Development

In the early 1980s, the Fédération Internationale du Sport Automobile (FISA) reorganized their classification structure for motorsports. Two new categories, known as Group B and Group C, were designated for use in the World Sports-Prototype Championship. Porsche had developed the 956 for the Group C rules, and following the 956's debut, began work on developing a Group B car. A initial prototype concept, named the Porsche Gruppe B, debuted in 1983, after which plans were made to build the car for production and provide racing versions for customers as had been done with the 956.

By time the Gruppe B had been launched as the production 959 in 1985, Group B rules had been altered by FISA to better suit the class' use in the World Rally Championship rather than the Sports-Prototype Championship. Plans to develop multiple customer cars for sports car racing were therefore scrapped by Porsche, but development continued on the production of car which could be factory run in order to put the car's development to use. This lone racing car, built on 959 chassis No. 10016, became known as the 961.

The new 961 retained much from the 959 road car, including most notably the four-wheel drive system that was uncommon in sports car racing at the time but allowable under the Group B regulations. The system was modified to distribution power more to the rear wheels rather than the balanced distribution of the 959. The driver adjustable damper and suspension systems were removed and replaced by a racing unit that could only be adjusted from by the pit crew, but was more reliable for endurance racing.

The 961's engine was a Porsche Type-935 unit. This twin-turbocharged engine was not only used in the 959, but was also the Group C 956 and later the 962C. This racing development helped the 961 run higher boost level than the standard 959. This resulted in a peak power output of 680 hp (510 kW). The brakes were also adapted from those developed for the 962C. Bodywork was replaced with lighter panels to bring the car down to a weight of 1,150 kg (2,500 lb), while the rear wing and front fascia were replaced with modified designs in order to create more downforce. Dunlop, who already supported Porsche's factory 962C team, supplied the tyres for the 961.

When the 961 was completed in 1986, Porsche had not yet built enough 959s to satisfy the Group B regulations for homologation. Due to this, the 961 had to be classified under International Motor Sports Association's similar GTX class.