Off radar

The fallen stars
Mercedes C111

Investment for the future

Photo credit: Daimler Media, Mercedes-Benz, Wheelsage

The end of the 60s was marked by great technological innovations and achievements for humanity, such as the Apollo 11 moon landing in 1969. The period was also a particularly fertile one for cars, with considerable experimentation happening among the manufacturers at the time. After shelving the SLX project, the new board at Mercedes gave the green light to a series of experimental cars to develop new technical solutions. The code name within the company was C101, later changed to C111 to avoid legal disputes with Peugeot who had registered and patented the three-digit acronyms with a zero in the middle for its models. 

1969. The first rudimentary prototype of the Mercedes C111 equipped with a three-rotor Wankel engine, mounted at the rear, during the first track tests in Germany. Note the design of the front that will remain very similar over the years

The first tests began in 1969 in Germany, under the direction of Rudolf Uhlenhaut – the creator of the 300SL – on the tracks of Untertürkheim and Hockenheim, with the first prototype equipped with a curious aluminium body just over a metre high from the ground, but above all a three-rotor Wankel engine, a solution that at that time seemed to have a great future after it appeared in the NSU Spider in 1964.

Towards the first definitive model: the C111 with wool tufts for the wind tunnel during the first tests that preceded the official presentation in 1969

The first appearance of the three-rotor C111 was at the Frankfurt Motor Show in 1969 in the characteristic ‘Weißherbst’ colour (named after a well-known German rosé wine), and it immediately aroused great interest especially thanks to the countless technical innovations that made it appear almost as a spacecraft when compared to the cars of the period: body panels made of fiberglass reinforced plastic combined with an innovative riveting and gluing technique, rear suspension inspired by the F1 cars of the time, and mind-blowing performance with a top speed of 270 km/h and acceleration from 0 to 100 km/h in just 5 seconds.

The first real C111, with its three-rotor Wankel engine, is presented at the Frankfurt Motor Show in 1969 in the colour ‘Weißherbst’ – the name of a rosé wine – which will characterize all future versions

The biggest flaw of the car, however, was the lack of torque at low and medium revs, a problem that led the technicians to develop a second prototype with an elongated wheelbase and more refined aerodynamics, presented a few months later at the 1970 Geneva Motor Show, equipped with four rotors and a maximum power output of 350hp. 

After the disappointing first performance tests of the Wankel engine, the C111-II was presented in 1970 at the Geneva Motor Show equipped with a four-rotor Wankel engine. The very beautiful and advanced line was also further refined

However, the prospect of stricter anti-pollution regulations and the oil crisis of 1973 put an end to the idea of Mercedes offering its customers a Grand Tourer with a Wankel engine. And so the project was steered towards one that looked into ways to enhance the potential of diesel engines, which at the time were viewed with scepticism. 

Rudolf Uhlenhaut, car development director of Mercedes, with the compact three-rotor Wankel engine used in the first experiments. Despite a promising start, this technology could not demonstrate its superiority over classic piston engines

The C111 was subsequently transformed into a real laboratory with a third prototype equipped with a 2999cc supercharged 5-cylinder diesel engine, used for promotional purposes towards diesel fuels, obtaining several speed records on the Nardò track, among which an average speed of 316 km/h (195.4 mph) over a 12-hour cruise stands out as a real achievement.

This image shows an indisputable advantage of the Wankel engine: its compactness, so much so that the C111 was able to accommodate 3 generous suitcases

The final development of the C111 was the fourth version, conceived in 1975 to break the world track speed record of 355 km/h, unofficially held by the Porsche 917/30 Can-Am at the Talladega Circuit. Equipped this time with a twin KKK-turbocharged 4800cc V8 petrol engine producing 500hp, along with heavily modified and extremely aerodynamic bodywork on the front and tail, on 4th April 1979, again in Nardò, the car recorded an average lap-speed of over 403 km/h. Despite the construction of 12 examples, including all the versions, the C111 played a significant role for experimentation but remained a dream for the many who would have liked to possess one.

1977. The first version of the diesel-powered C111, again in orange, is joined a year later by the record-breaking model which, in classic Mercedes tradition, abandoned the colour to achieve maximum lightness
The C111-III on the Nardò track at full speed. The record of 316 km/h over 12 hours set with a turbocharged 2999cc diesel engine is extraordinary
Old rivalries return: after the pre-war challenges for speed records between Mercedes and Auto Union, this time the car to beat was the Porsche 917/30 Can-Am, from which the C111-IV with its supercharged petrol engine, snatched the world speed record on a track at over 400 km/h