Mercedes-Benz C291

The 1991 season marked the introduction of the FIA’s new, and controversial, 3.5 litre formula which replaced the highly successful Group C category that had been used in the World Sportscar Championship since 1982, though due to a small number of entries for the 3.5 litre formula heavily penalised Group C cars (which were subject to weight penalties and started behind the new-style C1 entries on the grid) were allowed to participate in the season's C2 category.

To meet the new regulations Mercedes-Benz came up with an all-new car; the C291 which was designed by its racing partner Sauber.

One survived and is on display in the Carl Benz Museum in Ladenburg, Germany.^[3] Another one is located in the Michael Schumacher Collection in Cologne, and this is the Autopolis-winning chassis.

The primary feature of the new regulations was the use of a 3.5 litre naturally aspirated engine. This made it impossible for Mercedes-Benz to use the engines from its previous Group C cars. Also, to produce similar power to the Group C cars a 3.5 litre naturally aspirated engine had to be very high-revving and be constructed from different materials in order to rev highly.

Unlike Jaguar's XJR-14 who had the readily available and proven Ford HB V8 engine from the Benetton B190B Formula One car (the engine regulations for the new 3.5 litre formula were identical to Formula One), Mercedes-Benz had to design an all-new purpose-built racing engine and its M-291 3.5L flat-12^[4] unit was the result. The engine produced about 550–600 brake horsepower (410–450 kW) compared to about 730 brake horsepower (540 kW) produced by the 5.0 litre twin turbo V8 found in the C291's predecessor, the Mercedes-Benz C11.

Unlike the Jaguar XJR-14, the C291 resembled previous sports-prototypes, despite the fact that the redesign of the Le Mans Circuit de la Sarthe in 1990 meant cars with their low drag design, top-end power, straight-line acceleration and top-speed characteristics were no longer required^{[citation needed]}. Unlike the Jaguar (and latterly the Peugeot 905B) the Mercedes still featured a full-width low-drag single-tier rear wing and no front wing. This resulted in the car having a higher top speed than the Jaguar (and only slightly less than old Group C cars).^{[citation needed]}

However, this, allied to the characteristics of the 3.5 litre engine, meant the car would have slower acceleration above 150-170 mph than most Group C cars, therefore not taking advantage of the low-drag design, and conversely the low-drag design meant the car was slower in the corners than the Jaguar and Peugeot's 905B, this time not taking advantage of the lower kerb weight of 750 kilograms (1,653 lb).^{[citation needed]} Overall the C291 was not as fast as a contemporary Formula One car around some circuits used by the Grand Prix fraternity, and was a lot slower at Le Mans' Circuit de la Sarthe in 1991.^{[citation needed]}