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.