Group C2

Group C was a category of motorsport, introduced by the FIA in 1982 for sports car racing, along with Group A for touring cars and Group B for GTs.

It was designed to replace both Group 5 Special Production Cars (closed top touring prototypes like Porsche 935) and Group 6 Two Seater Racing Cars (open-top sportscar prototypes like Porsche 936). Group C was used in the FIA's World Endurance Championship (1982–1985), World Sports-Prototype Championship (1986–1990), World Sportscar Championship (1991–1992) and in the European Endurance Championship (1983 only). It was also used for other sports car racing series around the globe (All Japan Sports Prototype Championship, Supercup, Interserie). The final year for the class came in 1993. Broadly similar rules were used in the North American IMSA Grand Touring Prototype series (GTP).

The roots of the Group C category lie in both FIA Group 6 and particularly in the GTP category introduced by the ACO at Le Mans in the mid-1970s. GTP was a class for roofed prototypes with certain dimensional restrictions, but instead of the more usual limits on engine capacity, it placed limits on fuel consumption. The FIA applied the same concept in its Group C rules. It limited cars to a minimum weight of 800 kg and a maximum fuel capacity of 100 litres. With competitors restricted to five refueling stops within a 1000 kilometer distance, the cars were effectively allowed 600 litres per 1000 kilometers. The FIA hoped this would prevent manufacturers from concentrating solely on engine development; in the late 1970s, a few manufacturers (especially Porsche and Lancia) had dominated sports car racing by simply increasing turbocharger boost pressure, especially in qualifying trim — the 3.2 L Porsche 935 was capable of more than 800 hp. Engines had to be from a recognized manufacturer which had cars homologated in the FIA's Group A Touring Car or Group B GT Car categories.

...
Wikipedia