Mazda created a six-minute short documentary about the restoration of its Le Mans 787 four-rotor vehicle.

      Mazda Motorsports via YouTube

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      Only one rotary engine has ever triumphed at the 24 Hours of Le Mans, and it's an exhilarating powerhouse that revs to 9,000 rpm and emits flames from its exhaust. Luckily, Mazda aims to ensure this engine and the vehicles it powered do not become mere dusty relics in a museum. Recently, the automaker's motorsports division released a video on its YouTube channel showcasing the maintenance of the large four-rotor engines.

      After years of perseverance, Mazda clinched victory at Le Mans with the 787B in 1991, coinciding with the beginning of production for the FD RX-7 road car. However, instead of the recognizable two-rotor 13B engine that equips the RX-7, the 787B is fitted with a four-rotor variant called the R26B. Estimated to produce around 700 horsepower in race configuration, this engine features rotors similar to those found in Mazda's road vehicles from that era, yet almost every other aspect differs. It even utilizes three spark plugs instead of two to enhance fuel efficiency.

      Mazda Motorsports via YouTube

      This reliance on unique parts makes sourcing replacements quite challenging, but the robustness of these engines suggests that any which endured a racing career should perform well in retirement. According to Mazda, the major components are holding up admirably. This longevity is attributed to upgrades like ceramic apex seals and more durable tension springs that help mitigate the “chatter” caused by the steel apex seals commonly found in road cars bouncing within the rotary housing at high rpm.

      Those seals—located at each corner of the triangular rotor to maintain compression—are a recognized vulnerability in rotary engines. Mechanics also focus on monitoring the inner surface of the housing, which can contract when overheated, causing the seal to break. During a rebuild, the thickness of the inner surface is compared to that of the outer surface (which experiences less heat) to verify it meets specifications.

      Inside the Mazda 787: Rebuilding a 4-Rotor Le Mans Prototype

      Following Mazda's groundbreaking victory in 1991, rule modifications rendered the rotary engine less competitive. Mazda would stand as the sole Japanese manufacturer to win Le Mans until Toyota's first victory in 2018. Mazda made a return to premier sports car racing in IMSA, initially with a diesel engine and later with a gasoline turbo-four that positioned it as somewhat of an underdog before ceasing operations after the 2021 season.

      While the MX-5 Cup remains highly enjoyable, the absence of an active Mazda factory sports-car racing program increases the significance of keeping the vintage racers operational. They serve as a crucial reminder of Mazda's capabilities when it strives for excellence and represent an era unlikely to be replicated. Despite ongoing speculation, a new Mazda rotary sports car is improbable in the current business climate, much less a new rotary-powered Le Mans challenger.