Mazda 787B

The Mazda 787 and its derivative 787B are Group C sports prototype racing cars that were developed by Japanese automobile manufacturer Mazda for use in the World Sportscar Championship, All Japan Sports Prototype Championship, and the 24 Hours of Le Mans from 1990 to 1991. Designed to combine a mixture of the Fédération Internationale du Sport Automobile (FISA) Group C regulations 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 787s had reliability that 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. As of 2025, this remains the only victory by a car not using a reciprocating engine design. It was the first victory by a Japanese manufacturer, and the only such victory until Toyota won the 2018 24 Hours of Le Mans.

A total of two 787s were built in 1990, while three newer specification 787Bs were built in 1991.

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. The 787 name was used instead of 777 to indicate a two-step improvement over the 767, and possibly over pronunciation difficulties of 777 in Japanese. 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 more granular variable intakes and three spark plugs per rotor instead of the 13J's two along with ceramic apex seals and variable length trumpets, among other modifications for increased efficiency. This allowed for a maximum power output of 900 hp (670 kW) at a redline of 10000 RPM, which was reportedly limited to 700 hp at 9000 RPM during the 1991 race at Le Mans for longevity^{[citation needed]}. The five-speed gearbox manufactured by Porsche, also mounted on the 767 and 787 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 in front of the windshield. A Gurney flap was located at 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 rotary engine. In the past, Mazda had developed variable-length telescopic intake runners to optimize engine power and torque for varying RPM levels. For 1991, the system became continuously variable, rather than previous versions that had steps for different engine ranges. This resulted in an increased torque of 608 N⋅m (448 lb⋅ft) at 6,500 rpm. The 787B's onboard ECU controlled the action of the telescopic intake. Another main improvement was the change in suspension geometry which allowed for larger wheels to be fitted along with carbon ceramic brakes, a first for a Mazda racing car.

The engineers at Mazdaspeed determined that fuel efficiency was crucial for achieving victory so they restricted the redline of the engine to 8,500 rpm thus reducing the power output to 650 hp (485 kW). Emphasis was put on high cornering speeds rather than attaining high top speeds at the straight sections of the track. Jacky Ickx was appointed as an advisor to guide the team in preparing the car.