BMW K4

The BMW K4 was an experimental car of the Bayerische Motoren Werke from 1939 and 1940, built on a pre-production chassis of the BMW 335. Like the K1 of the year before, it was a four door upper class saloon designed for high cruising speed and low fuel use, with five full seats, a streamlined pontoon body with integrated fenders and a Kamm tail with a cut-off rear. The body was not designed at BMW but by Professor Wunibald Kamm at the research institute for motor vehicles and vehicle engines in Stuttgart, and the coachbuilder Reutter in Stuttgart built it in 1940. The exact drag coefficient is not recorded but lies between the 0.23 of the K1 and the 0.37 of the shorter Kamm car K3. Unlike the K1 it wore the BMW kidney grille. The water cooled straight six of 3,485 cubic centimetres from the 335 made 66 kilowatts at 3,500 revolutions a minute, driving the rear wheels through a four speed gearbox with an overdrive, and the Kamm cars could change tyre pressure from the dashboard while driving to cut rolling resistance. The K4 weighed about 1,500 kilograms. The public reacted partly with harsh criticism of its looks, so it stayed a one off, and its trace is lost at the end of the war.