Group C

The roots of the Group C category lie in both FIA Group 6 and, particularly, 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 that placed limits on fuel consumption rather than engine capacity. The FIA applied the same concept in its Group C rules, limiting 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 km distance, 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, manufacturers — especially Porsche and Lancia — had dominated sports car racing by increasing turbocharger boost pressure, with the 3.2 L Porsche 935 capable of more than 800 hp. Engines had to be from a recognised manufacturer homologated in the FIA's Group A Touring Car or Group B GT Car categories. All races were to be contested over at least 1000 km, usually lasting more than six hours.

Ford (with the C100) and Porsche (with the 956) were the first constructors to join the series. The 956 used a turbocharged boxer engine already tested in the 1981 Group 6 Porsche 936. Other manufacturers that eventually joined included Lancia, Jaguar, Mercedes, Nissan, Toyota, Mazda, and Aston Martin, many of which also took part in the IMSA championship.

With costs increasing, the FIA introduced the Group C Junior class for 1983, intended for privateer teams and small manufacturers. It limited cars to a minimum weight of 700 kg and a maximum fuel capacity of 55 litres, effectively allowing 330 litres per 1000 kilometers with five refueling stops. Engines had to come from a manufacturer homologated in Group A or Group B. Although originally expected to use two-litre normally aspirated engines, most cars in practice used either the 3.5-litre BMW M1 engine or the new 3.3-litre Cosworth DFL. Alba, Tiga, Spice, and Ecurie Ecosse with Austin-Rover and later Cosworth-powered cars were among the most competitive. The low cost of these cars led to their use in national championships such as the short-lived British BRDC C2 Championship. Group C Junior was formally renamed Group C2 for 1984.

By 1989, Group C's popularity was nearly as great as Formula One. Cars were breaking over 400 km/h on Le Mans' Mulsanne Straight — the WM-Peugeot recorded the highest speed of 405 km/h (252 mph) during the 1988 event. The FIA attempted to turn Group C into a formula series, restricting performance of cars built to the original rules and benefiting teams using F1-sourced 3.5-litre engines. The new formula cars were more expensive than the C1 cars, and the new engines were unaffordable for privateer teams like Spice and ADA. A lack of entries meant the 1993 Championship was cancelled before the first race. However, the ACO still allowed Group C cars to compete — with restrictions — at the 24 Hours of Le Mans.

The 1994 Le Mans was the last race in which Group C cars were permitted. The Dauer 962 Le Mans, a former C1 car entered in Group GT1 as a road-legal GT car, won the race after transmission problems for a leading Toyota 94C-V. The 962 was subsequently banned. A few C1 racers were also allowed to compete in the newly formed Japanese GT Championship, marking a final year of competition. The Porsche WSC-95, which won the 1996 and 1997 Le Mans races, used the monocoque of the Jaguar XJR-14 combined with Porsche 962 mechanicals.

The FIA's Group C formula was designed primarily for the World Endurance Championship, but several smaller series also adopted the regulations. The Deutsche Rennsport Meisterschaft allowed Group C cars to compete from the 1982 season until 1985, when the series was reformed as the ADAC Supercup — which allowed only Group C cars until 1989. In Great Britain, the Thundersports championship combined various car types with C Junior cars, later replaced by the C2-only BRDC C2 Championship, which lasted until 1990. The European Interserie championship also allowed Group C cars, though with a different class structure. In Japan, the All Japan Sports Prototype Championship was created in 1983, while the Fuji Long Distance Series began allowing Group C cars the same year; both concentrated solely on Group C from 1989 and lasted until 1992, when they were cancelled alongside the World Sportscar Championship.

This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.