Wankel Fever: The Mercedes-Benz C 111

Debut of the Mercedes-Benz C 111-II at the Geneva Motor Show from 12 to 22 March 1970, the second version of the experimental vehicle with a four-rotor Wankel engine.

A visionary design in form, drive system and materials: The Mercedes-Benz C 111 thrilled both the motoring world and the public when it celebrated its debut at the International Motor Show (IAA) in Frankfurt/Main 50 years ago. The rotary-engined sports car never entered series production, yet rapidly became an icon. From 1975 on it provided the basis for successful record-breaking cars. Coinciding with the anniversary: the book "Mercedes-Benz C 111" by Hartmut Jundt and Wolfgang Kalbhenn will be published at the end of October 2019. Based on the extensive original documentation in the Mercedes-Benz Classic archives, it tells the story of the vehicle and rotary engine development at Mercedes-Benz.

Blank cheques: In September 1969, visitors to the International Motor Show (IAA) in Frankfurt/Main crowded around the futuristic super-sports car presented to the world public by Mercedes-Benz in sheer amazement. Was this swing-door model perhaps the legitimate successor to the legendary 300 SL "Gullwing" (W 198) of 1954? This was not the case, although well-heeled customers even sent blank cheques to Untertürkheim. The C 111 remained purely an experimental vehicle, it never entered series production. Only twelve examples of the two versions appearing in 1969 and 1970 were produced.

Revolutionary: In this fascinating mid-engine sports car, Mercedes-Benz was above all testing the powertrain with its rotary piston engine on the principle developed by Felix Wankel. The C 111 of 1969 was powered by a three-rotor Wankel engine with a chamber volume of three times 600 cubic centimetres and an output of 206 kW (280 hp). After further development, the C 111-II presented just six months later at the Geneva Motor Show in spring 1970 featured a four-rotor engine with four times 600 cubic centimetres and 257 kW (350 hp).

Wankel fever: Mercedes-Benz had already been working on the Wankel rotary engine since the early 1960s. Draft vehicle designs were produced in parallel with this, for example the mid-engine SLX sports car conceived by Bruno Sacco and designed by Mercedes-Benz designer Giorgio Batistella from 1964. The company's engineers continued to develop the Wankel engine further with great courage and pioneering spirit, despite major challenges. In 1967 Head of Development Prof. Dr Hans Scherenberg reported that the rotary engine had an around 50 percent higher fuel consumption than a reciprocating V-engine of the same cubic capacity. In the end, fuel consumption and emissions were the major stumbling blocks for series production of the powerful and smooth-running Wankel engine. Mercedes-Benz finally ended its Wankel engine development in early 1976.

C 101: It was under this project name that concerted realisation of the Wankel sports car began at the end of 1968. It was the responsibility of the head of passenger car development, Rudolf Uhlenhaut, while the project manager was Dr Hans Liebold, head of pre-development. The fascinating design was created by a team under Joseph Gallitzendörfer, while Bruno Sacco, who had recently moved from pre-development to styling, coordinated body development for the spectacular sports car. The first test drive of the first complete vehicle took place at Hockenheimring on 15 July 1969. The experimental vehicle was then unveiled to the public under the name C 111 at the International Motor Show (IAA) in September – this was how Mercedes-Benz avoided a conflict with model designations trademarked by Peugeot with a zero as the middle digit.

Innovation platform: Alongside the Wankel engine, technologies were tested in the C 111 that had only been realised in series production vehicles to a limited extent, among them bodies of glass-fibre reinforced plastic (GRP) and joining techniques such as adhesive bonding and riveting. This technological look into the future was underlined by the visionary design of the wedge-shaped super-sports car.

Weissherbst: The iconic character of the C 111 was also reinforced by the unusual paint finish in metallic orange. The designation "Weissherbst" derived from wine-making referred to the glowing orange/rosé colour of these popular wines. The vehicle displayed at the IAA show in Frankfurt was the first C 111 in this spectacular paint finish. The other vehicles in the first series, which were used as demonstration vehicles during the IAA show, were still in a white paint finish, but were later likewise repainted in "Weissherbst".

Headlines: Admiration for the C 111 was reflected in the media: "The four-rotor version would not only be the most comfortable and smooth, but also the fastest car of this kind. I am firmly convinced that there would be thousands of customers for such a car around the world," Paul Frère wrote in the motoring magazine "auto motor und sport", issue 8/1970. "The car that takes your breath away," said the "Deutsche Auto-Zeitung". The motoring magazine "Road & Track" wrote the following in November 1969: "If we tell them how much we like it [the C 111], maybe they'll produce it." The magazine "Hobby" put the further improved C 111-II on its title page in April 1970, and described it as the "four-rotor rocket from Untertürkheim".

Ultimate trumps: The experimental vehicle not only thrilled with its visionary concept, but also with a performance that was outstanding in its time. The first version of the C 111 reached a top speed of 260 km/h, and the C 111-II even managed 300 km/h. In the "Car Quartet" card games of the early 1970s, this catapulted the C 111 into the superleague. In fact the C 111 became the title motif in Quartet games like "German Cars" by Altenburg-Stralsunder Spielkarten (ASS) in 1970/71 and "Fast sports cars" by Bielefelder Spielkarten in 1970.

Records: In 1976 the second career of the C 111 began as a record-breaking car with reciprocating engines. Two versions with five-cylinder turbodiesel engines (C 111-II D in 1976 and C 111-III in 1978) were created, as well as the C 111-IV with a V8 petrol engine in 1979. On the high-speed track in Nardò, Italy, the C 111s established numerous new records, one of them the circuit world record with 403.978 km/h by the C 111-IV on 5 May 1979.

Drivable dream: In 2014 the specialists at Mercedes-Benz Classic restored one of these dream sports cars from their collection to drivable condition. To preserve the few still available Wankel engines for the future, they installed an M 116 3.5-litre V8 engine. This engine had already been installed in a C 111 for comparative and test purposes in 1970 – precisely the same car that was again being used. This means that the legendary C 111 takes an active role in classic events and can be seen up close by fans of the brand.