By akademiotoelektronik, 06/03/2023

24 Hours of Le Mans 1991: behind the scenes of Mazda victory – 1/2

The road to victory in the Sarthe region began in Belgium in 1981. The 24 Hours of Francorchamps was then the benchmark race for touring cars. That year, Pierre Dieudonné was at the wheel of a Mazda RX-7 with a rotary engine prepared in England for driver-preparer Tom Walkinshaw: "I remember a stint at the end of the night, explains the Belgian, Tom leaves me the car. I had noticed that the gearbox was sticking. I ask him: “we are second, it is unexpected. Do we insure? “No, he replies, you take 500 rpm more before changing gear: we break or we win”. The BMWs give in to this Division 2 car. The agile and sonorous RX-7 allows Mazda to win its first international race.

=> The 24 hours of Francorchamps 1981 in video

A few months later, the Belgian driver was summoned to the Tokyo Motor Show to celebrate the victory and shake hands. There he met Takayoshi Ohashi, owner of Mazdaspeed. This large concession in the Japanese capital has a competition department. And the man intends to create a small prototype – adapted to the new C-Junior category, the equivalent of our LMP2s – for the world endurance championship and the 24 hours of Le Mans. Mazda had dipped a toe in the Sarthe a decade earlier, with rotary piston engines mounted on Lola and then Sigma chassis.

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Mazdaspeed’s first trial balloon was the 717 C. The catfish-shaped machine was designed in the workshops of Japanese specialist Mooncraft. The twin-rotor of the RX-7 is pushed beyond 300 horsepower. In each chamber, there is a triangular "piston" (the rotor) transmitting the energy produced by the combustion of the fuel to the engine shaft via a crank pin. The solution is compact and reduces friction. "He was foolproof," recalls Pierre Dieudonné. The only thing that could be a problem was over-revving by missing a gear. If you go over 9,000 rpm, you risk damaging a ridge segment in the combustion chamber.” Luckily that didn't happen at the 1983 24 Hours of Le Mans, Takashi Yorino, Yōjirō Terada and Yoshimi Katayama managed to win the C-Junior class… 68 laps behind the overall victorious Porsche.

“The driving force behind the program has always been Mazdaspeed boss Mr. Ohashi, with his iconic driver Yōjirō Terada. They were the ones who would make contacts, look for budgets, obtain technical assistance. But for the first few years these efforts were piecemeal.

Photo: Mazda

Over the next few years, support from headquarters in Hiroshima grew. In Sarthe, the brand is among the applied students. The 757 then 767 and 767B often appear at the finish (7th place in 1987 and 1989), but behind in relation to the battle between the automotive giants: Porsche, Jaguar, Sauber-Mercedes then Toyota and Nissan... But the high note of the rotary engine makes it one of the most popular cars with the public.

Rotary on borrowed time

The end of the decade brought big changes. The Berlin Wall falls, the Japanese real estate market collapses (precipitating the archipelago into economic crisis) and the International Motorsport Federation intends to put an end to Group C regulations and their consumption limits. Future prototypes of the brand new world sports car championship – note the disappearance of the term endurance – will be based on conventional 3.5-litre naturally aspirated engines from F1. Time is running out for the Mazda rotary program.

Yasuo Tutsotomi – head of Mazda engineering and product planning – took over the reins a few months earlier. It commits yen and requires engine manufacturers to jump 100 horsepower on the atmospheric 13J quad-rotor. Hired as a freelancer, the British engineer Nigel Stoud designed the 787: “The problem was always the packaging, explained this pioneer of computer-aided design to our colleagues at Autosport in 2018. The engine was as long as a 6- cylinders in line”. The R26B develops around 700 hp in racing configuration. Five years after Jaguar and its XJR-6, Mazda is (finally) adopting the carbon fiber monocoque. A single radiator takes place in front of the nose, reducing the number of air inlets. The rear wing is placed at the lowest. Mazda is also rejuvenating its workforce. To the young and talented German driver Volker Weidler – who arrived in 1989 – Mazdaspeed added two other sprinters also from F1: Johnny Herbert and Bertrand Gachot.

1990 was, however, a difficult season in the Japanese championship and at Le Mans. In the Sarthe, the two 787s give up due to mechanical problems. And during the night, Bertrand Gachot is also scared: “We encountered electrical problems and the headlights went out while I was driving. I had just passed the pit entrance. I had to do a complete lap to bring the car back to the box, with the risk that another competitor would come faster behind me without seeing me. To signal myself, I slapped the accelerator, which generated flames one meter high”.

“Because of these reliability problems, the other manufacturers did not realize how far we had progressed in 1990,” says Pierre Dieudonné. The following year, Mazda thus escaped the penalties imposed by the federation to discourage brands wishing to participate in the world championship with their old Group C cars. 12, Mercedes C11 and Porsche 962 C must now exceed the ton on the scale. But the Mazdas, which would run under IMSA approval, can finally keep their 830 kg. The shooting window is open. It now remains to review the management of the team...

=> Read the second part of this article by clicking here

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