The C 111 study from 1969 was an embodiment of futuristic design merged with innovative technology. The vehicle served as a platform for testing different drive system concepts, and with its bodywork made from glass-fibre-reinforced plastic, it put its stamp on the design of state-of-the-art sports cars. The lightweight skin of the coupé, whose design opened up new possibilities for aerodynamics, was bonded to the steel sub-frame. This path continued with the even more elegant C111-II, presented at the Auto Salon in Geneva in 1970.
The C111 Type I was powered, not by a reciprocating piston engine but a wankel engine. The performance of the C111 with a three-rotor wankel engine was convincing from the very outset. With its 280 hp, the wankel drive unit accelerated the vehicle to a top speed of 260 km/h, the sprint from 0 to 100 km/h took a mere 5 seconds. The 1970 C111-II was powered by a large four-rotor wankel engine. This powerplant delivered 350 hp and made a top speed of 300 km/h possible. And this second C111 accelerated from 0 too 100 km/h in a highly respectable time of 4.8 seconds. However, this powerful performance contrasted with a poor efficiency level which cannot be improved through technical modifications. Due to its high consumption levels and too-high pollutant emissions, Mercedes-Benz gave up work on this engine variant in spite of its impressive running smoothness and compact size.
Instead of this, Mercedes-Benz pressed ahead with the further development of the diesel engine, frowned upon as loud a sluggish. In 1976 engineers installed a three-litre 5-cylinder turbo-diesel engine motor in a C 111-II. Thanks to turbocharging and charge-air cooling the vehicle, now dubbed C 111-IID, delivered 190 hp to the road and impressed at the Italian high-speed track of Nardo with its spectacular speeds. The average speed of this lightning test drive was 252 km/h, and Mercedes-Benz proved that diesel-powered vehicles could certainly also sprint.