Press Release
Testing of the diesel engine
Then, in the fall of 1973, a boycott of the oil-producing countries brought about the so-called oil crisis and crude oil, hitherto an inexpensive commodity, became a precious resource. Developers were requested to come up with new engines which, more than anything else, used the expensive fuel sparingly. The most obvious proposition was the low-consumption diesel engine but the compression-ignition unit was still thought to be sluggish and noisy. There had certainly been examples of either vice in automotive history but the diesel engine had long since been developed into a refined power unit, perfectly capable of driving sporty passenger cars.
In 1976, Mercedes-Benz decided to disprove the old prejudice - and what could have been better suited to providing counter-evidence than a C 111 with diesel engine? The engineers installed a three-liter naturally-aspirated compression-ignition engine with five cylinders in the C 111-II for the first tests. In the car, now called C 111-IID, the OM 617 LA engine developed as much as 190 hp, thanks to turbocharging and intercooling, as opposed to the 80 hp output of the production engine which powered the Mercedes-Benz 240 D 3.0 (W 115, Stroke Eight) and, at a later stage, other models. In June 1976, the C 111-IID reached spectacular speeds on the test track at Nardo near Lecce in Italy. In the course of 60 hours, four drivers established a total of 16 world records - thirteen of these applying to diesel-engined cars and three to cars in general, irrespective of their type of engine. During the tests, an average speed of 252 km/h was recorded, and Mercedes-Benz proved impressively that diesels also have sprinter qualities.
Second career as a record-breaking car
The success of the sparsely modified C 111-II in Nardo spurred the developers on to new heights. This time, they did not create a design study for a road-going sports car but a thoroughbred racing car for the sole purpose of establishing speed records: the C 111-III. The new car was built in 1977; it was narrower than the first C 111, had a longer wheelbase and perfect aerodynamic properties, thanks to complete streamlining and rear airfoils. In 1978, the C 111-III lined up at the start in Nardo. Once again, a diesel engine growled under the silver-painted plastic bodywork. While this engine had been derived from a production unit, it had been tuned to develop 230 hp and gave the streamlined car a top speed well over 300 km/h. With this Silver Arrow, Mercedes-Benz established nine absolute world records in the late 1970s.
However, the C 111 was still to take the final evolutionary step towards becoming an all-out racing machine. The last version of the sports car, the C 111-IV presented in 1979, broke the track record by reaching a speed of 403.978 km/h. This time, it was no longer a diesel engine working under the plastic skin but a V8 gasoline engine with a displacement of 4.5 liters and an output of 500 hp. The shape of the bodywork was equally a far cry from the first version. Ten years on, and the bodywork crafted with esprit and courage in 1969 had become a slim, elongated rocket with two airfoils and massive spoilers in a silvery livery.
Setting the standards for the design of modern sports cars
Even the first C 111 hadn't deserved its nickname, "test lab on wheels". As well as incorporating highly innovative parts and assemblies, the coupe set the standards for the design of modern sports cars.
The gullwing doors, retained for all four series of the C 111, identify this charismatic experimental car as a member of the legendary Mercedes-Benz sports car family. These doors, hinged at the roof, developed into hallmarks of Mercedes-Benz sports cars. They first featured on the filigree 300 SL (W 194) which was entered in racing in 1952; from this car, a road-going sports car (W 198/I) was derived of which just about 1,400 units were built between 1954 and 1957. The coupe with its breathtaking metal skin on a spaceframe was powered by a modified version of the six-cylinder in-line engine from the 300 "Adenauer Mercedes". Rudolf Uhlenhaut, head of the passenger car testing department at Mercedes-Benz and creator of the 300 SL, topped the development of the dynamic sports car line with a 300 SLR in 1955. The engine of the "Uhlenhaut Coupe" was based on that of the open-top 300 SLR racing sports car in which Stirling Moss and Denis Jenkinson won the Mille Miglia in 1955: the sports car was powered by the eight-cylinder in-line engine from the company's racing cars at the time but the plans to put the SLR coupe to the acid test in the Carrera Panamericana long-distance race in Central America were thwarted.
Gullwing doors - intriguing to this day
The stylish gullwing doors of the SL and SLR models of the 1950s are still being regarded as an expression of elegance and dynamism today - and quite rightly so. However, they were also a technical necessity, dictated by the filigree spaceframe which had to be combined with wide, stability-enhancing sills, thereby requiring door hinges at the top. On the four series of the C 111, the gullwing doors were design quotations relating back to the Silver Arrow era. The C 112 research car presented at the IAA in 1991 equally featured gullwing doors hinged at the roof.
This elegant door design did not return to series production until the up-to-date Mercedes-Benz SLR McLaren. The new coupe with styling features reminiscent of the current McLaren-Mercedes Formula One racing car swings its doors upwards into the air as elegantly as the C 111 did 35 years ago and the 300 SL 50 years ago. There is, however, one major difference: after half a century, the dream of a series-produced road-going Mercedes-Benz racing coupe has finally come true.
The C 111 reviewed by the press
In November 1969, Ron Wakefield, writing for "Road & Track", directly compared the C 111 with Italian sports cars: "During my first ride I was immediately struck by the quietness of the power unit inside the car. It was far quieter than, say, a 12-cyl. [Lamborghini] Miura though not so hushed as the Ford V8 of the De Tomaso Mangusta. As the engine wound up I once again noticed the motorcycle sound and it was a smooth, steady pull all the way up to what seemed like much too early a shift at 7000 rpm."
In April 1970, racing driver and journalist Paul Frère wrote in "Motor" about his experiences in trial driving: "This car provides an unequalled combination of comfort and handling, the latter being quite definitely in the racing car class."
In late 1969, "Auto Motor & Sport" wrote: "The quiet running of the Wankel engine and the virtually complete absence of wind noise will initially deceive you into wrongly assessing the actual speed. When you think you're doing 150 or 160 km/h, a glance at the speedometer will quickly tell you that you are in fact doing 240 km/h. Incidentally, 7000 rpm in fourth gear correspond to 226 km/h."
