Auto Union Type D

The Auto Union Grand Prix racing cars types A to D were developed and built by a specialist racing department of Auto Union's Horch works in Zwickau, Germany, between 1933 and 1939.

Of the 4 Auto Union racing cars, the Types A, B and C, used from 1934 to 1937 had supercharged V16 engines, and the final car, the Type D used in 1938 and 1939 (built to new 1938 regulations) had a supercharged 3L V12 that developed almost 550 horsepower. Wheelspin could be induced at over 100 mph (160 km/h), and the marked oversteer that persisted throughout the cars' development made all the Auto Unions difficult to handle, although the smaller engined Type D was a bit easier to drive because of the smaller engine and the half as much space it took up in comparison to the 6L V16 in the previous Type C. This was due to the fact that all 4 tyres were the same size, the big engines (particularly the 6L V16 in the Type C) were very heavy, and racing cars during this time did not have aerodynamic downforce- which effectively meant there was no way to keep the rear stable, therefore making it impossible to get rid of the car's oversteer. Automotive performance physics and aerodynamics were not really understood until the 1960s, and even with the Auto Union's sophisticated suspension, a compromise on setups could not be achieved to sufficiently dial out the oversteer- and the narrow tyres used at the time were of no help either; the limits of grip that these tyres could provide showed how far ahead of their time the Auto Union cars were.

Between 1935 and 1937 Auto Unions won 25 races, driven by Ernst von Delius, Tazio Nuvolari, Bernd Rosemeyer, Hans Stuck and Achille Varzi. Their main competition came from the Mercedes Benz team, with Auto Union proving particularly successful in the 1936 and 1937 seasons. Known as the Silver Arrows, the cars of the two German teams dominated Grand Prix racing until the outbreak of World War II in 1939.

Having been made redundant from Steyr Automobile, Dr. Ferdinand Porsche founded Porsche in Stuttgart, with engineering colleagues including Karl Rabe, and financial backing from Adolf Rosenberger. Unfortunately, car commissions were low in the depressed economic climate, so Porsche founded the subsidiary company Hochleistungsfahrzeugbau GmbH (HFB) (High Performance Car Ltd.) in 1932 to develop a racing car, for which he had no customer.

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