The 540 K Cabriolet of 1934 was called by Mercedes 'Special Roadster'. It had a 5-liter eight-cylinder engine. The dimensions for bore (86 mm) and stroke (108 mm) are strangely twisted in relation to today. The long stroke resulted in a good torque. This required the rated speed to be low with 3400 rpm. With compressor the engine reached 118 kW (160 hp) without 74 kW (100 hp). Also, the production number was with 25 copies in two years far below the present, even with luxury cars.