Hubraum
Between 1929 and 1940, DKW produced a less well remembered but technically intriguing series of rear-wheel drive cars called (among other names) "Schwebeklasse" and "Sonderklasse" with two-stroke V4 engines. Engine displacement was 1,000 cc, later 1,100 cc. The engines had two extra cylinders for forced induction, so they appeared like V6 engines but without spark plugs on the front cylinder pair.