MAZDA 787B ROTARY LE MANS

Mazda’s victory against all the odds at the 1991 Le Mans 24hr remains the stuff of legend. By Paul Davies

The starting grid for the 1991 Le Mans 24 hour would have been a quieter place had the FIA pressed ahead with its original plans for the event. The governing body was keen to push a new set of regulations that would see all sports-prototype cars running 3.5L conventional piston engines. Jaguar, Mercedes, and Peugeot all built cars to the new rules, but when it became clear that there were never going to be enough new spec entrants developed in time, it was decided that cars conforming to the previous generation group C regulations would be allowed to race too.

These would, however, not be able to start higher than 11th as the first five rows would be reserved for the 3.5L cars. This resulted in Peugeot lining up in first and second spot, despite being only third and eighth fastest in qualifying. Three of the top five quickest cars were Mercedes running old regulation 5L twin-turbo engine cars after both Jaguar and Mercedes entered their previous generation prototypes having failed to qualify with their new regulation 3.5L cars. For the race, Mercedes and Peugeot were looking like the teams to beat.

Mazda chose to take advantage of the ability to run ‘old’ cars too, entering three 787B’s in the race. The quickest 787B in qualifying had been only twelfth fastest and would start down in nineteenth once the rules governing the top ten positions were applied. This was Mazda’s thirteenth attempt at Le Mans and, apart from a junior class win in ’84 when a Mazda powered Lola T616 finished tenth overall, success for Mazda had been conspicuous by its absence. Before the race began, there was little to suggest that this year was going to be much different.

However, the 787B was more than a tweaked 787, a car which had suffered two engine related retirements at Le Mans the year before. The car’s designer, Nigel Stroud - a man who had experience in F1 and who had previously worked on the Porsche 962 - heavily revised the car for the ‘91 season. The 787B sported carbon brakes (a first for any Mazda race car), a carbon fibre and Kevlar monocoque, plus heavily revised geometry which allowed the fitting of wider wheels, and perhaps most notably, a revised R26B rotary engine.

The R26B is arguably the feature that defines the 787B. Rather than using conventional pistons, the R26B was a rotary engine which utilised two triangular rotors. A single rotor version of this engine design was first used by Mazda in the 1960’s when it became the only manufacturer to really push the rotary engine concept, however despite racing rotary engine cars for decades, success for the concept had always been limited. For the ’91 season the rotary engine had been extensively reworked. It now had 3 spark plugs per rotor, ceramic rotor tips and a very clever constantly variable intake system. The variable intake system was not new, however previously it had operated in steps. The new constantly variable intake system allowed the engine to produce more torque, more of the time. Paired with the other upgrades the R26B could produce 900bhp, though this was detuned to around 650-700bhp for endurance racing where reliability and economy are key.

What the engine also produced was noise! Words cannot accurately convey the sound of the 787B, however, to say that the R26B screamed all the way to 9,000 rpm would certainly not be hyperbole. There were reports that around some parts of the circuit spectators were warned when the 787Bs were approaching so they could cover their ears. Indeed, it has been suggested the noise led to the 787B being banned, however the truth is simply that it was the victim of the changes in regulation.

At Le Mans, reliability is key. Mazda were confident in the reliability of their engine, and the 5 speed Porsche gearbox it was mated to was also known to be reliable. The team had avoided 200kg of ballast (which the larger capacity, non 3.5L regulation cars had to carry) after the team successfully argued that their engine was not large capacity and could therefore run with a starting weight of only 830kg. That starting weight meant a power-to-weight ratio over 800bhp per tonne.

Controlling such power required skill and for the number 55 car that skill came in the form of Volker Weider, a previous Formula 3 champion and Formula One driver, Johnny Herbert, another F3 champion and three times F1 victor, and Bertrand Gachot, also a relatively successful racer in various Formulas, who was not long out of prison having been locked up for using CS spray on a taxi driver he had got into an altercation with in London. That Johnny Herbert was racing at all was quite remarkable having nearly lost a foot in an accident three years prior in which the front of the Formula 3000 car he was driving was ripped off. Indeed, by the end of the ’91 Le Mans race, having driven a double stint and having run out of water, Herbert had to be removed from the 787B by medical staff, suffering from exhaustion and crippling pain in his ankle.

As the ’91 race got underway the Mercedes team were on the move, quickly moving up to take position behind the lead Peugeots. They would go into the night in first, second and third places after both Peugeots suffered issues. However, the Mazdas were on the move too. The team threw caution to the wind and instructed their drivers to go flat out. Passing cars on track, and others when they fell by the wayside, the number 55 Mazda was now behind the three lead Mercedes, and keeping them honest. The number 31 Mercedes suffered gearbox issues causing it to lose 9 laps in the pits, the number 32 Mercedes was damaged when it hit debris, and as the night wore on the Mazda which had started nineteenth was sitting pretty in second.

This wasn’t what anyone had expected and with confidence in the reliability of their car, team Mazdaspeed ordered their drivers to push hard. They did. Perhaps pushed to run faster than they wanted to, the number 1 Mercedes suffered overheating problems which proved to be terminal. And so, as the 24 hours drew to a close, the strange screaming engine Mazda which had started nineteenth and which had not really been seen as much of a contender, was now out in the lead.

Johnny Herbert crossed the finish line 2 laps clear of the Jaguar in second, cementing the first and only Le Mans victory for Mazda, for a rotary engine car and the first Le Mans victory for a Japanese manufacturer. The regulations brought in for ’92 meant a rotary car would never compete again, but the Mazdaspeed team had done it – they had proven the rotary could win on the most famous stage in endurance motorsport.

The 787B had triumphed where its predecessors had stumbled and it was pure elation for Japan and the Mazdaspeed team. While Mazda would return in ’92 with a 3.5L conventional engine car, they would find no success and would not enter the following year. 1991 had truly been the high tide moment for the Mazda team and for the screaming rotary engine.