From 1976, the FIA World Championship for Makes would be ruled by the Group 5 regulations as the top category. Essentially, the cars would have to be based on a homologated model from Group 1 to 4 with all modifications allowed from these groups being applicable with more freedoms given.
Engine capacity became free although original homologated engine block and architecture would have to be retained. Gearbox location had to be as per production and original driving wheels would have to be retained as well as the suspension design (McPherson, rigid rear axle, etc.).
It was to be all about aerodynamics with the main criteria being that wings covered the wheels while retaining the original shape and for the downforce, well, they had to be inscribed in the frontal projection of the car. Then and up front, they could not exceed more than 10% of the wheelbase and no more than 20cm over the original coachwork limits and under the horizontal plane of the wheel hub. For the rear it was the same but of 20% when referring to the wheelbase and no more than 40 cm when considering the coachwork.
At the beginning, Porsche and BMW battled at World Championship level as well as in the Deutsche Rennsport Meisterchaft – Germany’s domestic Championship – with the Porsche 935 and BMW 3.0 CSL, both having evolved in true monsters. But Porsche set a benchmark with the 935, a true and complete new car purposely made to fit the rules while BMW sort of upgraded its all-conquering Group 2 model and it was proving hard to cope with the Stuttgart boys.
From 1977, BMW introduced its new car, the BMW 320 Group 5. Based on its E21 shell, the car was to be Munich’s answer to Stuttgart. Originally a normally aspirated design, fitted with its all conquering BMW M12/7 engine based on the M10 block, the car was basically to be a lightweight hard charger in order to beat the all mighty 935s. Soon, BMW’s own network started running the car around the world but above all, the German domestic Championship would turn sensational with each tuner more or less adding its own development to the model.
By 1979, Schnitzer was working hard against the DRM Porsche opposition and Ford had joined the game as well with the Zakspeed Capri. By then, the BMW had been equipped with a Turbo engine, the Schnitzer M10 Turbo design, basically Schnitzer’s own Formula 2 development of the M10 with a DOHC head but here it became equipped with a big turbo in order to battle Porsche and Ford on the same ground.
End of 1979, Schnitzer pushed it a little further and this was more or less due to the rules and freedom having evolved. At the 9th round of the Championship at Zolder and during the ADAC-Westfalen-Pokal-Rennen, Manfred Winkelhock rolled out the so-called BMW 320 “Extreme” version of the model as it was nicknamed under the Rödenstock Würth Team / Schnitzer banner.
It was nothing else than a big aerodynamic development of the 320, a sort of chopped-off version with lower lines and larger and supposedly better bodywork. But more or less, it followed a very specific trend happening in the German Championship. This version of the 320 Group 5 had no more connection with the original car than the name, front grille and roof. As Zakspeed came with the full spaceframe Turbo Capri and the Kremer boys were pushing the development as far as possible, the DRM had become a complete silhouette series, even with a supposed Lotus 47 or “Europa” being based on a TOJ chassis. Yeah, it was just looking like production and if you look at the cockpit picture of the Beemer, it looks like a monocoque or added chassis through aluminium panels.
But back to the car and debut, it was short-lived actually with Winkelhock reverting to his normal 320 for the Qualifying and Races due to teething problems.
The real deal came together during Round 11 of the Championship at the Nürburgring and during the ADAC-Bilstein-Super-Sprint held on the very short course of the Betonschleife of 2.292km. Winkelhock toook part in the Aeroheck car while Walter Brun inherited his old girl. Winkelhock scored a 3rd place finish in Division 2 for the real debut of the car while he did qualify 4th.
And it would go on from 1980 with Hans-Joachim Stuck driving the Würth liveried car while Walter Brun would inherit the original Winkelhock car, the nickname would also change as the car would be equipped with an aerodynamic enhancing rear window and become the Aeroheck. But still, the Porsches and Fords ended up being faster…