| Mercedes-Benz M21 | |
| Manufacturer: | Mercedes-Benz |
| Production: | 1933–1936 |
| Configuration: | Straight-six |
| Bore: | 70mm |
| Stroke: | 85mm |
| Displacement: | 2L |
| Valvetrain: | 12-valve, SOHC, two-valves per cylinder |
| Power: | 40hp |
| Torque: | 83lb.ft |
| Fuelsystem: | Carburetor |
| Fueltype: | Gasoline |
| Compression: | 5.75:1 |
| Oilsystem: | Dry sump |
The Mercedes-Benz M21 engine is a naturally-aspirated, 2.0-liter, straight-6, internal combustion piston engine, designed, developed and produced by Mercedes-Benz; between 1933 and 1936.[1] [2] [3] [4] [5] [6] [7]
The side-valve six-cylinder engine had a capacity of 1,961 cc which produced a claimed maximum output of 400NaN0 at 3,200 rpm. The engine shared its 85mm piston stroke length with the smaller 6-cylinder unit fitted in the manufacturer's W15 model, but for the W21 the bore was increased by 5mm to 70mm. The stated top speed was 98 km/h (61 mph) for the standard length and 95 km/h (59 mph) for the long bodied cars. Power from the engine passed to the rear wheels through a four-speed manual transmission in which the top gear was effectively an overdrive ratio. The top two ratios featured synchromesh. The brakes operated on all four wheels via a hydraulic linkage.[8]
During the model's final year, Mercedes-Benz announced, in June 1936, the option of a more powerful 2,229 cc 550NaN0 engine, which was seen as a necessary response to criticism of the car's leisurely performance in long bodied form.[9]