Mercedes-Benz 1962. The C 111
 

While the Wankel engine had the advantages of being compact design and very quiet, the Wankel engine’s inherent problems – poor degree of efficiency, due to the elongated, variable combustion chambers of the rotary-piston principle could not be overcome by any degree of engineering ingenuity. 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 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 says Mercedes-Benz.
https://www.youtube.com/watch?v=ekSRRvGPlnI

https://www.youtube.com/watch?v=XBoMKJ6ptNY

https://www.youtube.com/watch?v=0sAvkXDd3Ic
FLASHCar
If that wasn’t enough, Mercedes-Benz, in just a few months showcased the C 111-II at the Geneva Motor Show. The three rotor Wankel engine was swapped for a four-rotor Wankel engine with an output of 350 hp.The engine, a DB M950 KE409 model, also had 600 cubic centimetres of volume per rotary piston and was the most advanced of the rotary piston engines developed at Mercedes-Benz. The engine transmitted its power to the rear wheels via a five-speed transmission, accelerated the C 111-II from a standing start to 100 km/h in 4.8 seconds and gave a top speed of 300 km/h.