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Proposed Mercedes gull-wing successor in 1969 used rotary engine

Sleek rotary-engined coupe so awed show-goers that several blank cheques were passed

Published: September 23, 2019, 10:30 PM
Updated: September 29, 2019, 7:48 PM

Mercedes-Benz C 111

At about the time that Mazda was starting to produce its rotary-engined sport coupes, another manufacturer was looking at also building a sporty car using the German developed powertrain.

Mercedes-Benz C 111-II

At the 1969 IAA in Frankfurt, Mercedes-Benz introduced the world to a gull-winged C 111 concept many believed was the long-awaited successor to the iconic Mercedes-Benz 300 SL. The sleek mid-rear rotary-engined coupe so awed show-goers that several blank cheques were handed over to Mercedes to go toward purchasing the production version that never materialized.

The C 111 was designed by a team led by Joseph Gallitzendörfer, with the composite fibreglass body (painted in a unique orange metallic and bonded to the chassis and platform by adhesives and rivets) handled by Bruno Sacco. The vehicle was completed and tested at Hockenheimring in summer 1969, prior to its fall public unveiling in Frankfurt.

Mercedes-Benz C 111 wind testing

Only 12 C 111s were ever produced — experimental cars, meant to try out the advancements in powertrain, drivetrain and aerodynamics. At their hearts were versions of Felix Wankel’s invention, the rotary engine.

The car introduced to the world in Frankfurt used a 1.8-litre 3-rotor engine, which had been in Mercedes-development since the early ’60s, putting out 280 hp. Six months later, the engine had grown to 2.4 litres with the addition of a fourth rotor and power had grown to 350 hp.

Head of Mercedes-Benz passenger car development Rudolf Uhlenhaut with Mercedes-Benz C 111 3-rotor Wankel

“The 4-rotor version would not only be the most comfortable and smooth, but also the fastest car of this kind,” wrote Paul Frère in auto motor und sport. “I am firmly convinced that there would be thousands of customers for such a car around the world.”

But as Mazda discovered over the years, fuel consumption and emissions proved to be insurmountable obstacles for production approval. Before the original engine was developed, Head of Development Prof. Dr Hans Scherenberg had reported fuel consumption that was 50% higher than the same size piston V-engine and after several years of massaging, by 1976 Mercedes had abandoned development of the engine.

Mercedes-Benz C 111

As impressive as the performance of the rotary was (originally pushing the car to a top speed of 260 km/h and then 300, in its second iteration), it wasn’t the only thing the C 111 had going for it, and once the company abandoned the Wankel rotary and switched to traditional internal combustion engines in the car’s original design, it went on to set records with 5-cylinder turbodiesel and V-8 gasoline engines, with the latter setting a circuit world record average speed of 403.978 km/h, a decade after its auto show debut.

Mercedes-Benz Classic restored one of the original cars in 2014, equipping it with a 3.5-litre V-8, which ironically, had been used as comparison engine to the Wankel rotary back in 1970.