Mazda’s Le Mans-Winning 787B Rotary Engine Rebuild: A Six-Minute Deep Dive

Only one rotary engine in history has ever won the 24 Hours of Le Mans, and it’s a machine that revs to 9,000 rpm while shooting flames from its exhaust. Mazda’s motorsports division has now released a six-minute mini documentary detailing the meticulous rebuild process of the legendary four-rotor engine that powered its 1991 victory.

Mazda’s 787B: The Only Rotary Le Mans Winner

Mazda’s breakthrough came in 1991 with the 787B, a car powered by the R26B—a four-rotor engine estimated to produce around 700 horsepower in race trim. Unlike the two-rotor 13B found in the FD RX-7, the R26B featured nearly all-new components, including a unique triple-spark-plug setup designed to improve fuel efficiency.

The Engineering Challenges of a Four-Rotor Rebuild

Finding replacement parts for the R26B is a significant hurdle due to its rarity. However, Mazda reports that the engine’s durability—thanks to innovations like ceramic apex seals and heavier-duty tension springs—has allowed surviving units to remain in excellent condition. These upgrades help prevent the “chatter” caused by steel apex seals in road cars, which bounce against the rotary housing at high RPM.

Rotary engines face unique wear issues, particularly with the inner surface of the housing, which can warp from overheating and break the seal. During a rebuild, mechanics compare the thickness of the inner surface to the outer surface (less exposed to heat) to ensure it meets specifications.

From Le Mans Glory to Racing Hiatus

After Mazda’s historic 1991 win, rule changes made the rotary engine uncompetitive. The automaker remained the only Japanese manufacturer to win Le Mans until Toyota’s victory in 2018. Mazda later returned to top-tier sports car racing in IMSA, first with a diesel engine and later with a gasoline turbo-four, before ending its factory program after the 2021 season.

While the MX-5 Cup continues to thrive, the absence of a current Mazda factory sports-car program makes the preservation of vintage racers like the 787B even more critical. These cars serve as a testament to Mazda’s engineering prowess and a reminder of an era unlikely to be repeated.

“Despite persistent rumors, a new Mazda rotary sports car is unlikely in today’s market, let alone a rotary-powered Le Mans contender.”

Watch Mazda’s Six-Minute Rotary Engine Rebuild Documentary

The mini documentary, released on Mazda’s official YouTube channel, offers a rare behind-the-scenes look at the rebuild process for the 787B’s four-rotor powerplant. It’s a must-watch for racing enthusiasts and rotary engine fans alike.