AUTC meaning in General ?

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, after the company bought a design by Dr. Ferdinand Porsche in 1933.

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. All of the designs were difficult to handle due to extreme power/weight ratios (wheelspin could be induced at over 100 mph (160 km/h)), and marked oversteer due to uneven weight distribution (all models were tail heavy). The Type D was easier to drive because of its smaller, lower mass engine that was better positioned toward the vehicle's center of mass.

Between 1935 and 1937, Auto Unions won 25 races, driven by Ernst von Delius, Tazio Nuvolari, Bernd Rosemeyer, Hans Stuck and Achille Varzi. Auto Union proved particularly successful in the 1936 and 1937 seasons. Their main competition came from the Mercedes Benz team, which also raced sleek, silver cars. 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.