The body was all about weight reduction. Thin sheet metal, thin windows, plastic parts and the elimination of insulation helped decrease the total vehicle weight of the racing cars to less than the 900 kg required for the new model to be homologated. At the same time, the aerodynamics were improved. The aim was to minimise lift on the front and rear axles at high speeds in order to achieve more neutral handling.
Engineers Hermann Burst and Tilman Brodbeck, together with stylist Rolf Wiener, then developed a rear spoiler for the first time, testing it in the wind tunnel and on test tracks. The aim was to retain the original unified bodystyle of the 911, to compensate for the drawbacks of the sloping rear with suitable and stylistically appropriate measures, and to improve the aerodynamics of the 911.
Sheet metal and wooden blocks on the engine cover were initially used during the trials, as precursors to the finished ducktail design. In the wind tunnel, the engineers identified the flow pattern at the rear and the changes with the new tear-off edge. As the test car stood on a weighing bridge with one balance per axle, the new lift values could now be worked out. After three days in the wind tunnel with three different variants, the engineers settled on an initial measurement for the height and width of the rear spoiler.
Their new findings: the elevation of the new ducktail spoiler pushed the 911 Carrera RS 2.7 closer to the road when the car was driven at speed and supplied the rear engine with additional cooling air. The effect was achieved without any increase in drag – on the contrary, in fact.
Together with test driver Günter Steckkönig, photographers and designers, the developers travelled to the Hockenheimring to test what they had discovered in the lab on the road. The photographer took photos of the side of the Porsche from a specified distance in order to work out the effect of the spoiler from the height of the body later on. Thanks to a defined measuring distance, the developers also determined the exact top speed. “During tests, we found that with a taller spoiler we could actually increase the top speed due to the decrease in drag,” explains Falk. “So we kept raising the rear spoiler upward by millimetres with sheet metal at the tear-off edge until we found the reversal point at which the drag increased again.” As a result, top speed was increased by 4.5 km/h.
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