At the Frankfurt International Motor Show (IAA) in September 1969, Mercedes-Benz presented an out-of-the-ordinary car: the C 111. The world queued up to see this “test lab on wheels” with its wedge-shaped body and upward-opening gullwing doors. The color, an orange metallic, originally designated “rosé wine”, also helped to rivet attention. Less conspicuous, but no less unusual, were the technical innovations. The body consisted of fibreglass-reinforced plastic and was riveted and bonded to the steel frame-floor unit.
The C 111 served to test the Wankel engine. A three-rotor unit developing 206 kW (280 hp) provided the propulsion power and permitted a top speed of 260 km/h (162 mph) – quite remarkable for the time. Just a few months later a thoroughly revised version of the C 111 was shown at the Geneva Motor Show. It featured a four-rotor Wankel engine with an output of 257 kW (350 hp). The car accelerated from standstill to 100 km/h (62 mph) in 4.8 seconds and attained a top speed of 300 km/h (186 mph).
Little more was heard about the Wankel engine; diesel technology now became the focus of research. And record-breaking versions of the C 111 again captured public interest: in June 1976, April 1978 and May 1979, the C 111 completed runs on the high-speed test track in Nardo in southern Italy, which produced several absolute world records over various distances.
On the first record run, the C 111-II D, almost unchanged on the outside in comparison with 1970, was powered by a thoroughly revised five-cylinder diesel engine displacing 3.0 litres; instead of the 59 kW (80 hp) of the production car it now developed 140 kW (190 hp). In 1978, the C 111-III developed and output of 169 kW (230 hp) with an additional intercooler. But this record-breaking car now had little in common with the original C 111. The silver-coloured body mounted on a floor unit with changed dimensions was even more thoroughly streamlined.
The record-breaking C 111-IV of 1979 came with further aerodynamic refinements, additionally featuring distinctive spoilers, a changed front end and two tail fins. Its propulsion unit was a 4.5 litre V8 engine from regular production, enlarged to displace 4.8 litres and generate 367 kW (500 hp). In this version the C 111-IV was no longer a pure research vehicle but one that achieved top-class sporting performance. And yet it was a source of numerous insights benefitting large-scale production.