Mazda 787B at the Monterey Historic Races 2004.
The Mazda 787 and its derivative 787B were Group C sports prototype racing cars built by Mazda for use in the World Sportscar Championship, All Japan Sports Prototype Championship, as well as the 24 Hours of Le Mans from 1990 to 1991. Designed to combine a mixture of the Fédération Internationale du Sport Automobile (FISA) Group Cregulations with the International Motor Sports Association (IMSA) GTP regulations, the 787s were the last Wankel rotary-powered racing cars to compete in the World and Japanese championships, using Mazda's R26B engine.
Although the 787 and 787B lacked the single lap pace of World Championship competitors such as Mercedes-Benz, Jaguar, and Porsche, as well as Japanese Championship competitors Nissan and Toyota, the Mazdas had reliability which allowed them to contend for their respective championships. The reliability of the cars eventually paid off in 1991 when a 787B driven by Johnny Herbert, Volker Weidler, and Bertrand Gachot went on to victory in the 1991 24 Hours of Le Mans. This remains as of 2014 the only victory by aJapanese marque as well as the only victory by a car not using a reciprocating engine design.
A total of two 787s were constructed in 1990, while three newer specification 787Bs were built in 1991.
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.
Other modifications made to the 787's design included a relocation of the radiators. Initially placed beside the cockpit on the 767, a new single radiator was integrated into the nose of the 787. Air moved from the blunt nose of the car underneath the bodywork and through the radiator before exiting at the top of the nose. A Gurney flap was affixed to the radiator exit to increase front end downforce. This new radiator location also meant a redesign of the doors of the car, where the old radiator design had been located. The intake in front of the door and exit behind were no longer necessary and were thus not included, giving the 787 a smoother bodywork design on top. To aid in rear engine and brake cooling, intakes were placed on the side bodywork, immediately above the exhaust cooling vents.
As before, Stroud's monocoque design was built from carbon and kevlar by Advanced Composite Technology in the United Kingdom. Carbon fiber body panels were affixed to the two initial chassis that were built in 1990.
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.