History of The Rotary Engine

NSU Ro80, 1967

DSC_0804

ENGINE: KKM 871 (Test Car)
DISPLACEMENT: 1.5 Litre Twin Rotor (2 x 746.6 cc)
POWER: 150 hp @ 6,000 rpm

ENGINE: KKM 612
DISPLACEMENT: 995cc Twin Rotor (2 x 497.5 cc)
POWER: 115 hp @ 5,500 rpm

After five years of development, the NSU Ro80 was presented to the public at the 1967 International Motor Show. Journalists had previously had the opportunity to have a look at the revolutionary car on 21st August 1967 at Solitude Palace. In the same year, it became the first German car to claim the “Car of the Year” title awarded by an international Jury. With a 115 hp dual-disc rotary engine and front-wheel drive, NSU embraced a new, exclusive class with the Ro80. Series production began in October 1967.

When the NSU engineers set about designing the Ro80, they faced a task which should really make any engineer happy: They were not hampered or curtailed by regulations or by restrictions from a previous model. As the intention right from the outset was to sell this car in the very highest price bracket, the NSU engineers were also able to opt for costly design solutions based on the very latest findings. The result was a car which the people at NSU believed represented the future. It was established right from the start that the new car should be given the NSU/Wankel rotary engine.

The body line of the new car was unusual. Claus Luthe, who was in charge of the small NSU Design Studio, designed a saloon car whose lines were considered bold, and which was regarded up to a point as futuristic and very aggressive. The bonnet remained very flat due to the characteristic low installation height of the rotary engine. There were no fashionable gimmicks or stylistic embellishments to be found anywhere – there were no chrome strips, no unnecessary glitzy pomp, simply a shape which stood out in its own right. Every single aspect of the Ro80 body was carefully designed with aerodynamics in mind; the wedge shape had an exceptional drag coefficient of just 0.355.

The typical shape of the body, in which the starting point of the rear window was located higher than the comparable point for the windscreen, had a beneficial side effect: The boot was very large. The behaviour of the Ro80 on the road can be summed up in one statement: serene, up to the limits and laws of physics. NSU achieved this excellent road handling thanks to a careful, albeit also very expensive design of the wheel guidance and spring components, with advanced MacPherson struts on the front wheels, and with semi-trailing arms at the rear combined with long-stroke dampers and a large wheelbase. The hydraulic steering also allowed the Ro80 to glide gracefully, and effortlessly through the corners.

The Iberian Red Ro80 above was a test vehicle in which a new generation of advanced rotary engines were trialled. The fuel-injected engine with individual nozzles provided 150 hp at 6,000 rpm and propelled the streamlined test car to a top speed of 210 km/h. The standard chassis handled the additional performance very well, the test models were merely equipped with a stabiliser on the rear axle and a wider wheel/tyre combination.

The last Ro80 rolled off the production line in Neckarsulum on 19th April 1977, with 382 of them produced in the final year. In total, 37,406 vehicles were built. The Volkswagen group thus said goodbye not only to the NSU brand, but also the rotary engine. All further development work on the rotary engine ceased in Neckarsulum in 1978.

The Engine of the Ro80

In the year that it was released, the Ro80 was equipped with a dual-disc rotary KKM 612 type engine producing 115 hp. In the first two years, the engine had dual ignition, after which it was switched to single ignition. In 1971, an additional fan-belt-driven air compressor (vane pump) and an exhaust gas afterburner were added in order to comply with emission limits.

The engine initially proved to be not quite fully developed, which meant that in the first few years engine damage was a frequent occurrence, particularly when the car was being used in city traffic. The reputation of the Ro80 was badly affected, despite a goodwill regulation to replace the engine offered by the NSU factory.

However, it was not always the engine that was at fault. Out of ignorance, an uncertain diagnosis, over cautiousness, but also to show courtesy to the new customers, some dealers sent engines back to the parent company that had minimal to no defect. Even engines with a dirty air nozzle were replaced “to be on the safe side”. For a while, the proportion of the engines sent in that were classified at the factory as being “without complaint” was 35%.

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