At the meeting of the Union of German Engineers, which took place in Munich, at the Deutsches Museum, designer Felix Wankel presented a rotary piston engine – a power plant that is completely new in design.
In the Wankel engine, the role of a kind of piston was performed by a triangular rotor. It rotated in a stationary housing with a special configuration. During work, a cavity of variable volume was periodically formed there, in which all stages of the four-stroke process were sequentially carried out.
A fundamentally important advantage of the Wankel engine was its adherence to the “rotation only” principle. There were no connecting rods, pistons or valves performing translational movement. This increased efficiency and also made it possible to simplify the design, reduce the dimensions and weight of the engine.
In 1963, at the IAA Motor Show in Frankfurt, the compact convertible NSU Wankel Spider was shown – the first car with a rotary piston engine intended for consumers. The following year he went into series. Engine with a chamber displacement of 500 cm3. had a power of 50 hp. With. and accelerated the car to 150 km/h. In 1964-67. 2375 of these machines were manufactured.
But this was only the first sign. In October 1967, at the Frankfurt Motor Show, a presentation of a much more solid model took place – the 4-door sedan NSU Ro 80. It had an engine with two rotors (2×497.5 cm3), which developed 115 hp. With. Among other features of the car, it is necessary to mention a semi-automatic gearbox – three-stage, with a torque converter. As well as independent suspension on all wheels and disc brakes.
Thanks to the small size of the engine, the length and height of which were just over half a meter (508 and 546 mm, respectively), the hood turned out to be quite low. The car as a whole had a wedge-shaped shape and excellent streamlining for those times: the drag coefficient was only 0.33.
It is no coincidence that the NSU Ro 80 model won the prestigious international title Car of the Year 1968 (“Car of 1968”). This car was produced for ten years – until 1977 inclusive. A total of 37,389 units were produced.
It is noteworthy that licenses for the Wankel engine were acquired by such reputable companies as Daimler Benz (1961), General Motors (1970) and Toyota (1971). In 1969, an experimental Mercedes-Benz C111 car with a three-rotor Wankel engine appeared. The following year, a four-rotor unit was installed on it, which allowed it to reach speeds of up to 290 km/h. But the car never went into production.
The most popular cars with a rotary piston engine were models from the Japanese company Mazda. The beginning, however, was modest: in 1967, the Mazda Cosmo coupe appeared, which was produced in a circulation of only 1,176 units. But already the RX-2 model (1970) was produced in the amount of 225,004 units. It had a two-rotor engine (2 x 574 cm3) with 130 hp. With. and developed 190 km/h. It was followed by the RX-3 (1971), RX-4 (1972, etc.). In 1978, the millionth Mazda car with a rotary piston engine was produced.
It must be said that the Wankel engine developed insufficient power at low speeds. And at high engine speeds, incomplete combustion of the fuel mixture occurred, which affected the composition of the exhaust gases. The emergence of increased environmental requirements was the main reason why cars with Wankel engines were eventually stopped being produced. Nevertheless, they remain one of the most striking innovations in the history of the 20th century automobile.