The 787B was an evolution of the 787, itself developed from the earlier 767 and 767B designs that Mazda had raced in 1988 and 1989. The 787 name was chosen to indicate a two-step improvement over the 767, bypassing 777 partly to avoid pronunciation difficulties in Japanese.
The defining change from the 767 was the engine. The 767's 13J Wankel rotary was replaced by the bespoke R26B, a four-rotor unit designed specifically for racing. The R26B shared a broadly similar layout and displacement concept with its predecessor but incorporated major advances: more granular variable-length intake runners, three spark plugs per rotor instead of two, ceramic apex seals, and variable-length intake trumpets. In maximum configuration the R26B was reported capable of 900 hp at 10,000 rpm, though for the 1991 Le Mans race power was deliberately restricted to around 700 hp at 9,000 rpm to prioritise durability over outright performance.
Other notable changes to the 787's design over the 767 included repositioning the radiators. The earlier side-mounted arrangement was replaced by a single radiator integrated into the nose, with air passing beneath the bodywork before exiting ahead of the windshield. A Gurney flap at the radiator exit generated additional front-end downforce. The monocoque was built from carbon fibre and Kevlar by Advanced Composite Technology in the United Kingdom. The gearbox was a five-speed unit manufactured by Porsche, carried over from the 767 and 787.
Following the 1990 season, Mazda's Mazdaspeed racing division developed the 787B with targeted improvements in pace and reliability. The most significant change was to the intake system: the R26B's telescopic intake runners, previously stepped for different engine RPM ranges, became continuously variable. This change increased torque to 608 N·m at 6,500 rpm. The car's onboard ECU managed the telescopic intake action.
Suspension geometry was revised to allow larger wheels, and carbon ceramic brakes were fitted — a first for a Mazda racing car. For Le Mans, Mazdaspeed's engineers prioritised fuel efficiency above all else, restricting the engine's rev limit to 8,500 rpm, reducing peak power to 650 hp, and placing particular emphasis on high cornering speeds rather than top-end straight-line velocity.
Three new 787B chassis were built for 1991, alongside the two surviving 787s, which were also fitted with the new intake system. The R26B specifications in 787B trim were: four rotors in-line, peripheral porting, chamber volume of 655 cm³ per rotor, total displacement of 5,240 cm³, maximum power of 515 kW (700 PS, 691 hp) at 9,000 rpm, maximum torque of 608 N·m at 6,500 rpm, and engine weight of 180 kg.
At the 59th 24 Hours of Le Mans, Mazdaspeed entered three cars: the number 55 (chassis 002, a new 787B) crewed by Weidler, Herbert, and Gachot, painted in an outrageous orange and green livery for sponsor Renown; the number 18 (787B-001) driven by Maurizio Sandro Sala, Stefan Johansson, and David Kennedy in the standard blue-and-white colours; and the older number 56 (a 787) for Pierre Dieudonné, Takashi Yorino, and Yojiro Terada.
Mazda was not a favourite. The 787Bs started 19th and 23rd on the grid, with the grid positions shifted back by seven places to accommodate the new 3.5-litre C1 class cars at the front. Team manager Ohashi made the decisive call before the race: rather than running the customary conservative strategy, he instructed the number 55 crew to drive as if in a sprint race, a decision made possible by the demonstrated fuel economy of the R26B and the reliability shown in Paul Ricard tests.
The number 55 car worked its way through the field. It moved to second when the leading Mercedes-Benz C11 of Michael Schumacher, Fritz Kreutzpointner, and Karl Wendlinger suffered a gearbox problem. At the 22nd hour, the 787B took the lead when the remaining C11 of Alain Ferté pitted with mechanical trouble. Herbert took the wheel for the final stint — refusing to yield despite dehydration — and brought the car across the line in first place, completing 362 laps and covering 4,932.2 km, both new records for the newly modified circuit layout. The two other Mazda entries finished sixth and eighth.
The winning car ran virtually without incident: a blown headlamp bulb and a precautionary rear wheel bearing change were the only interventions beyond routine pit stops. Herbert was so dehydrated on the finish that he required medical assistance and could not reach the podium, leaving Weidler and Gachot to take the victory celebrations.
The R26B's Le Mans victory remained, as of 2026, the only win at that race by a car not powered by a conventional reciprocating piston engine. The Wankel rotary's inherently smooth power delivery and compact dimensions offered packaging advantages, but its relative fuel consumption — managed carefully at Le Mans through the rev-limited strategy — had historically been a weakness.
After 1991, the R26B continued in other programmes. Mazda used the engine in the RX-792P for IMSA GTP competition and in the spaceframe FD3S RX-7, which returned to Le Mans in 1994 backed by Mazdaspeed. As of 2002, Autoexe Motorsport, with Yojiro Terada among its drivers, competed at Le Mans in a modified WR chassis using a 2.6-litre R26B four-rotor, though without finishing the race.
The 787B and its R26B engine became icons of Japanese motorsport. The car appears in major sim racing titles including Gran Turismo, Forza Motorsport, and Assetto Corsa, making it one of the most recognised historic racing cars in gaming culture. Mazda preserves the winning number 55 chassis at its museum in Hiroshima; two replicas exist, one at the Le Mans museum. The 787B's Le Mans victory was the first by a Japanese manufacturer; Toyota's 2018 victory was the second and only subsequent one.