From 1976 to 1981 the World Championship for Makes was open to Group 5 Special Production Cars and other production based categories including Group 4 Grand Touring cars and it was during this period that the nearly-invincible Porsche 935 dominated the championship. Prototypes returned in 1976 as Group 6 cars with their own series, the World Championship for Sports Cars, but this was to last only for two seasons (1976–1977). In 1981, the FIA instituted a drivers championship. 1982 to 1992 In 1982, the FIA attempted to counter a worrying climb in engine output of the Group 5 Special Production Cars by introducing Group C, a new category for closed sports-prototypes (purpose built racing cars) that limited fuel consumption (the theory being that by limiting fuel consumption, engine regulations could be more relaxed). While this change was unwelcome amongst some of the private teams, manufacturer support for the new regulations was immense. Several of the 'old guard' manufacturers returned to the WSC within the next two years, with each marque adding to the diversity of the series. Under the new rules, it was theoretically possible for normally aspirated engines to compete with the (expensive to maintain) forced induction engines that had dominated the series in the '70s and early '80s. In addition, most races ran for either 500 or 1000 km, usually going over three and six hours, respectively, so it was possible to emphasize the "endurance" aspect of the competition as well. Group B cars, which was a GT class, were also allowed to race, but entries in this class were sparse; combined with fatal accidents in rallying where the Group B class saw more popularity, the class (and European GT racing altogether) disappeared from the series, with sports-prototypes dominating the championship. Porsche was the first constructor to join the series, with the 956, but soon several other makes joined the series, including Jaguar Cars, Mercedes-Benz, Nissan, Toyota, Mazda and Aston Martin. As costs increased, a C2 class (originally named C Junior) was created for privateer teams and small manufacturers, with greater limits to fuel consumption. In this lower class, most cars used either the BMW M1 engine or the new Cosworth DFL, but, like in the main class, a variety of solutions were employed by each individual manufacturer. Alba, Tiga, Spice and Ecurie Ecosse were among the most competitive in this class. While the Group C formula had