Including the first two C111 prototype designs here: the C111 proper from 1969 with a Wankel engine, and a C111-II running a 3.5-liter V8. The way to tell them apart is that the V8-powered C111-II has open spaces in the rear flying pillars, while the C111-I has louvered and solid-looking pillars.
1969 Mercedes-Benz C111 and 1970 C111-II
The Mercedes-Benz C111 was a sports-car vision revealed in the late 1960s with a slant-nosed, mid-engine design far removed from any Mercedes passenger vehicle. It was part of the continuing quest to broaden the Mercedes brand into new segments, in this case the supercar market.
We will cover the orange-colored C111 and C111-2 models in a later article.
This post is dedicated to the much-later iteration on the theme from 1977 and 1978.
The original C111’s Wankel engine was shelved indefinitely by the early 1970s, and production of the car was a non-starter due to dramatic Wankel failures in Audi sedans in the late 1960s. This almost sunk Audi overall, by the way, and Mercedes wanted to avoid the same fate, understandably.
A revolutionary new diesel five-cylinder engine with advanced Bosch fuel and electronics systems was proven in 1975 and ran around in a normal Merc sedan as its prototype. But this diesel was fast and super powerful compared to all others before. Electronic fuel injection finally made turbochargers able to live up to their potential, doubling power outputs of diesel engines almost overnight.
Mercedes needed a light and sporty prototype chassis to really prove how amazing this new diesel was to the world. Plenty of C111 shells were still around, and the engine compartment was just the right size for the new 240D engine making 190-horsepower.
Mercedes found that the C111-III was faster than anyone ever expected.
And suddenly the long-held German dream of high-speed glory came flooding into the present. Let’s set records, they exclaimed!
Over the next few years, the C111-III evolved at warp-speed to implement not just this diesel, but all of Mercedes’ latest knowledge on lightweighting, aerodynamics, and safety tech. No one wanted a repeat of the tragic 1930s V-max record runs, so crude ABS and extreme attention to downforce and anti-lift were a big part of the program.
The aero refinements were extensive, with flush shutlines and shrouded block headlamps that were unheard-of at the time for production cars. The cD achieved by the C111-III is still impressive today: just above 0.183 is super sleek.
How serious about aero? This giant red tube fed air from the nose back toward the engine – passing right through the cabin en route.
The C111 became longer, more streamlined and eventually decked out with wings, splitters and aero additions galore.
All this effort and expertise worked: the C111-III set more than a dozen diesel speed records, and three overall records for any engine type.
It was a brave new world for turbodiesel, and the C111-III’s achievements helped kickstart the fuel’s adoption in S-Classes from the late 190s forward. The tech would trickle down and eventually dominate the luxury segment, and mid-market, of European car shoppers for the next four decades.
PAris is stepping up now against the sooting and filthiness that resulted from all this diesel running around their cities. The proposed diesel ban in Paris by 2020 is creating quite a kerfluffle for PSA and others — long devoted to mastering the art of the TD engine’s efficiency and live-ability.
The C111-III is where the diesel engine really matured into world-class tech. Its aero shell is just as lovely as a contribution to the Mercedes archives, however.