The 1991 24 Hours of Le Mans was the 59th Grand Prix of Endurance, and took place on 22 and 23 June 1991. It was also the fourth round of the 1991 FIA Sportscar World Championship season.
Mazda’s 787B, powered with a rotary model 26B Wankel engine, won in 1991, overcoming reliability issues in the older manufacturer cars. It was the first (and so far the only) Japanese manufacturer to win Le Mans, as well as the only non-piston engine car to ever win. It won against considerable opposition from factory-entered Mercedes, Jaguar and the new 3.5L Peugeot cars; and from privately entered Porsche 962’s, still competitive after 6 years.
At its heart, the initial design of the 787 was an evolution of the 767 and 767B designs that had been used by Mazda in 1988 and 1989. Many mechanical elements of the 767 were carried over by Nigel Stroud when he designed the 787, but with some notable exceptions. Foremost was the replacement of the 767’s 13J Wankel rotary engine. In its place, the brand new R26B was installed. The custom-built R26B featured a nearly identical layout and displacement, but included new design elements such as continuously variable intakes and three spark plugs per rotor instead of the 20B’s two. This allowed for a maximum power output of 900 hp (670 kW) which was limited to 700 hp during the race for longevity. Porsche’s five-speed gearbox was retained.
Following the 1990 season, Mazda continued development of the 787 chassis in order to make improvements on its pace and reliability. One major development was the intake system for the rotaries. In the past, Mazda had developed variable length telescopic intake runners to optimize engine power and torque for varying rpms. For 1991, the system became continuously variable, rather than previous versions that had steps for different engine ranges. The 787B’s onboard ECU controlled the action of the telescopic intake.
Three new 787Bs were built for 1991, while the two existing 787s were also upgraded with the new intakes.
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