History of The Rotary Engine

Audi 200 KKM, 1977

ENGINE: KKM 871
DISPLACEMENT: 1.5 Litre Twin Rotor (2 x 746.6 cc)
POWER: 170 hp @ 6,500 rpm

In 1976, Audi NSU began road testing the KKM 871 engine in the Ro80. To allow comparisons to be made, the engines were coupled with a 3-speed or 4-speed selective automatic gearboxes. On all versions, the top speed was over 210 km/h. The testing programme included very promising results. The KKM 871 would have been the ideal nit to power an upgraded NSU Ro80; however, the decision to abandon it had already been taken in Wolfsburg. The Ro80 did not fit the model policy of the VW group. This was by no means the end for the KKM 871: For the new Audi 100 (C2) appeared on the scene in October 1976. The opportunities for the KKM 871 re-emerged as the decision had not yet been made on whether to choose an Audi turbocharged 5-cylinder engine or develop a new 6-cylinder unit.

It was then decided at the end of 1976, in a large-scale campaign, to present the highly successful KKM 871 on the international stage. This also presented the opportunity to demonstrate the new level of scepticism among old licences or those still to be recruited towards the Wankel principle. As the company’s withdrawal from its own rotary activity from 1974 and discontinuation of the Ro80 due in April 1977, a move was already heralded from the NSU/Wankel commitment and thus the presentation had a certain tokenistic feel to it.

The engine was built on a small scale, modified according to the country of presentation and installed from the beginning of 1977 in a fleet of 20 of the new Audi 100 (C2, from 1976). There was a delay because the gearbox of the Audi 100 proved to be too weak. The Audi 100 with the KKM 871 was presented in Europe, in the USA, in Japan and during the Frankfurt Motor Show in September 1977. The primary target in Europe was Citroën and in the USA the focus was mainly on General Motors, but its reaction was fairly reticent.

Some of the Ro80 and Audi 100/200 models powered by the KKM 871 engine were still used as company cars following the official end of the KKM 871 development. Almost all of the company’s top executives, especially in Wolfsburg, had one of these fast-paced models parked on their drive. In 1982, Audi NSU presented Felix Wankel with the phased-out company car that belonged to the CEO Dr. Habbel, an Audi 200 KKM (above), to mark his 80th birthday.

The Engine of the Audi 200 KKM

In 1971, the decision was made at Audi NSU with the blessings of Rudolf Leiding, who was appointed Audi NSU boss in this year, to focus rotary development on a new design. The future of the rotary engine still seemed to be secure. The new engine with the abbreviation KKM 871 – named after the VW development assignment EA 871 – was a dual-disc rotary engine.

The KKM 871 was planned right from the outset for front-wheel drive and not just exclusively for Audi NSU. Consideration was also given to what Citroën wanted in respect of the CX model series which was being developed. The company also wanted to keep open the option of using the KKM 871 in a future Audi 100 in which it was scarcely possible to use a 6-cylinder in-line engine due to the front-wheel drive concept. Further project specifications were: a chamber size of around 750 cc in order to match the engine size (2x dual chamber volume), power and smoothness of a conventional 3-litre 6-cylinder engine, and do this within the installation space and weight of a 2-litre 4-cylinder engine.

The fuel consumption was to be at the level of the comparable 6-cylinder engine and the manufacturing costs were to be significantly cheaper than those in the engine of the Ro80. The most import measure was the study for a side inlet; however, a decision was only to be made following the evaluation of the test results in which, by way of comparison, the peripheral inlet was also examined using the KKM 886 single-disc version. Whereas the development of new reciprocating piston engines was already being stepped up in Neckarsulum, the decision on the production of the KKM 871 was put back ever further. This time it was used to examine further concepts: stratified loading with direct partial quantity injected and turbocharging were tested to increase the level of power to around 230 hp.

The fact that the engine ran with almost no vibration and the advantages in terms of weight and size meant that the rotary engine was also tested in the aviation industry. The dual ignition and the ease with which the engine could be modified to make it suitable for aerobatics were beneficial; the liquid cooling was less desirable. The Ro80 engine was also used for multiple aircraft, including the BX-110 test helicopter for the Swiss Berger. An aircraft called the Frantrainer, which was manufactured by the company Rhein-Flugzeugbau, was flown for the first time in 1973. It was propelled by two KKM 871, which were arranged in tandem and transferred their power to a propeller with seven blades around it. Audi NSU supplied four of the engines to the company, but declined to supply any more.