Blown Away: Porsche's First Turbo at Le Mans (Part Two)

July 3, 2015
Story By
John Brooks

From the perspective of Norbert Singer, who was given the responsibility of making the new Porsche 911 Carrera RSR Turbo competitive, there were a number of serious obstacles to overcome, mostly concerning contravening the laws of physics. Using a monocoque taken straight from the 911 production line meant that the starting point was a car that was both heavy and had a large frontal area, i.e. it would be aerodynamically inefficient, at least in terms of a pure racing car.

The first point of attack was to drastically reduce weight. Amongst the avenues explored Porsche considered using a NASCAR trick of the time. It was proposed to immerse the car's body in an acid bath to reduce the thickness of the metal by 50%, eventually the cost of that idea ruled that out. The next step was take more conventional steps, an aluminum rather than steel roll cage, really thin plastic/fiberglass doors, wheel arches and panels. Really ruthless attention to detail, no advantage being too small to take, brought the race car down to the 825 kilo mark - still 175 kilos more than the prototype opposition.

However running in the same class as the Matras and Alfa Romeos gave Singer considerable flexibility when addressing the practical matter of making the 911 Carrera RSR Turbo into a competitive racing car. The roof line was raised at the rear and flattened to improve air flow.

Perhaps the most distinctive feature was the huge rear wing which took full advantage of the revised aerodynamics.

Internally there were major changes too. With the engine and transmission hanging out at the rear on a 911 plus the turbocharger and ancillaries in the case of the RSR it is usual to have the fuel tank up front along with the battery and oil cooler. However in search of a more consistent set-up the fuel tank was moved to the centre of the car so that the weight distribution remained constant whether the tank was full or empty.

The rear weight bias (68%) combined with the wing gave very high levels of grip at the rear, it was ready to go racing. This level of grip could be exploited by 17 inch wide rims that were made of magnesium and had been built for the 917 project. The rear spoiler unit housed five NACA ducts to assist engine cooling. A flush rear window smoothed air flow to the spoiler whilst at the front, a deep wraparound air dam featured ducts for the oil tank.

The cockpit was very basic, none of the driver aids found today nor any form of data acquisition or telemetry, all seat of the pants stuff for both engineers and drivers.

The final touch that rounded this fearsome beast out was the Martini livery, it remains a very strong graphical statement.

Although the Le Mans 24 Hours was the focal point of the team's 1974 season Porsche raced the 911 Carrera RSR Turbo at most of the classic events that year with podiums at Watkins Glen (2nd) and Spa (3rd) being the highlights.

As for the Le Mans 24 Hours a pair of 911 Carrera RSR Turbos were entered by the factory, #21 for Helmuth Koinigg and Manfred Schurti and #22 for the lead pairing of Herbert Müller and Gijs van Lannep. In terms of outright speed the Porsche could not compete with the Matras and the Gulf-Mirages but the team placed its faith in reliability of the package. Their optimism was very nearly justified.

One by one the prototypes hit trouble till there was but one Matra left, that of Henri Pescarolo and Gérard Larrousse who had an 11 lap advantage over the #22 Porsche on the Sunday morning. Then panic overwhelmed the French pit as Pescarolo was stranded out on the circuit with gearbox problems, somehow he got the car back to the pits and the mechanics commenced repairs.

Ironically the gearbox had been designed for Matra by, you guessed it, Porsche. So with typical Porsche efficiency and customer service two of their best mechanics were despatched to the customer's pit to help with repairs - it took 45 minutes to get the gearbox ready meaning that the two cars were then on the same lap.

That was as close as it would get as the Porsche also hit transmission problem, losing fifth gear, forcing it to settle for second. Not too bad though for a racer that was really based on a road car.

The Oil Crisis and the economic downturn of the mid-70's meant that the proposed rule changes were delayed and then scrapped by FISA. Porsche cancelled their GT program in favor of developing the 934 and 935 racers for 1976. The 911 Carrera RSR Turbo was the most extreme 911 by far, at least at that point in the long history of the model, its huge rear spoiler and bulbous wheel arch extensions giving it an unforgettable appearance. It was a pioneer, being the first car to compete at La Sarthe with an exhaust driven compressor, a feature that even the very latest Porsche Le Mans winner has in common with its ancestor. It is a car that is seen once and not forgotten. (Photos: copyright and courtesy of Porsche AG, and John Brooks)

Blown Away: Porsche's First Turbo at Le Mans (Part Two)

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