Nov 12 2013
C111-II was first presented at Geneva Motor Show in March 1970. Compared to previous car this version had a significantly improved bodywork in terms of vision for the driver as well as aerodynamic efficiency – the Cd was 0.325, not bad at the time.
Improvements were also made to the engine. The C111-II consisted in a four-rotor Wankel engine with an output of 258 kW /350 HP that was fitted on a sheet steel chassis and covered by a fiberglass and reinforced plastic body. This made possible for the car to go from 0 to 100 km/h (0 – 62 mph) in 4.8 seconds and to a top speed of 300 km/h (186 mph). New modifications like a new variable intake system increased torque up to 540 Nm. The four-rotor engine was equipped with a single ignition and direct injection. The total curb weight was 1240 kg (2734 lbs). Other characteristics included a new configuration of the suspensions which allowed wider rims , a leather interior and the first anti-lock braking system.
When C111-II made its appearance at the Geneva Motor Show, interested parties send blank checks to Stuttgart to secure one of these cars for themselves. However, it was never been planned to produce the new Gullwing in series, and the C 111 was not to appear in showrooms. The coupe may have looked like the systematic further development of the Sport Light models from the 1950’s, but it was not a design study for a new SL: it was to serve as an experimental car.
The development department of Mercedes-Benz eventually succeeded in solving the engineering-design problems involved in the rotary-piston principle, especially in engine mechanics, but the problem of the Wankel engine’s poor degree of efficiency, due to the elongated, variable combustion chambers of the rotary-piston principle, was not to be overcome with technical modifications. This problem was simply inherent in the design: in a Wankel engine, the fuel burns within the space between the convex side of the rotary piston and the concave wall of the piston housing rather than the cylindrical combustion chamber of a reciprocating-piston engine. The variable, anything but compact combustion chambers of the Wankel engine were responsible for poor thermodynamic fuel economy as compared to a reciprocating-piston engine, resulting in significantly higher fuel consumption for the same output.
Furthermore, the hopes for this car to go into the production were destroyed by even more stringent emission legislation in a large number of countries and finally by the 1973 oil crisis. The engines of the first two C111 versions were straightforward gas-guzzlers. And since the pollutant content in the exhaust gas of the Wankel engines was also too high, Mercedes-Benz discontinued work on this type of engine in 1971, in spite of its impressively smooth running characteristics and compact size.
The 1970 C111-II was the last Mercedes-Benz fitted with a Wankel engine. The last engine mount was the four-cylinder rotary engine DB M950 KE409.
In retrospect, Dr. Kurt Obländer, head of engine testing in the C 111 project, described the Wankel engine as follows: ‘Our four-rotor engine with gasoline injection represented the optimum of what could be reached with this engine concept. The multi-rotor design called for peripheral ports for the intake-air and exhaust-gas ducts. We were able to solve the difficult problems in engine cooling and engine mechanics by technical means. But the main problem of the concept, its low thermodynamic degree of efficiency, remained. Due to the elongated, not exactly compact combustion chambers, fuel economy was poor, resulting in high fuel consumption and unacceptably high pollutant emissions. These drawbacks were inherent in the design principle.’
In 2000 the car’s developer Dr. Hans Liebold said: “The Wankel engine was not yet mature enough to be handed over to customers in line with company standards,”
The C111-II reviewed by the press
In April 1970, racing driver and journalist Paul Frère wrote in “Motor” about his experiences in trial driving: “This car provides an unequaled combination of comfort and handling, the latter being quite definitely in the racing car class.”