three-quarter+coupé

SUBJECT AREA: Automotive engineering, Land transport, Steam and internal combustion engines

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Wankel was first employed at the German Aeronautical Research Establishment, where he worked on rotary valves and valve sealing techniques in the early 1930s and during the Second World War. In 1951 he joined NSU Motorenwerk AG, a motor manufacturer based at Neckarsulm, near Stuttgart, and began work on his rotary engine; the idea for this had first occurred to Wankel as early as 1929. He had completed his first design by 1954, and in 1957 his first prototype was tested. The Wankel engine has a three-pointed rotor, like a prism of an equilateral triangle but with the sides bowed outwards. This rotor is geared to a driveshaft and rotates within a closely fitting and slightly oval-shaped chamber so that, on each revolution, the power stroke is applied to each of the three faces of the rotor as they pass a single spark plug. Two or more rotors may be mounted coaxially, their power strokes being timed sequentially. The engine has only two moving parts, the rotor and the output shaft, making it about a quarter less in weight compared with a conventional piston engine; however, its fuel consumption is high and its exhaust emissions are relatively highly pollutant. The average Wankel engine speed is 5,500 rpm. The first production car to use a Wankel engine was the NSU Ro80, though this was preceded by the experimental NSU Spyder prototype, an open two-seater. The Japanese company Mazda is the only other automobile manufacturer to have fitted a Wankel engine to a production car, although licences were taken by Alfa Romeo, Peugeot- Citroën, Daimler-Benz, Rolls-Royce, Toyota, Volkswagen-Audi (the company that bought NSU in the mid-1970s) and many others; Daimler-Benz even produced a Mercedes C-111 prototype with a three-rotor Wankel engine. The American aircraft manufacturer Curtiss-Wright carried out research for a Wankel aero-engine which never went into production, but the Austrian company Rotax produced a motorcycle version of the Wankel engine which was fitted by the British motorcycle manufacturer Norton to a number of its models.

While Wankel became director of his own research establishment at Lindau, on Lake Constance in southern Germany, Mazda continued to improve the rotary engine and by the time of Wankel's death the Mazda RX-7 coupé had become a successful, if not high-selling, Wankel -engined sports car.

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