Mercedes-Benz M121 engine

The M121 engine was developed just after the end of World War II. It was built in the Sindelfingen Works factory, which assembled the Mercedes Ponton Model series to which the engine belonged to. The M121 engine made its debut in 1955. It was the first generation of 4-cylinder engines from Mercedes Benz. The M121 replaced the less efficient M136 1.8-litre engine, a pre World War II engine that was introduced 2 years before in 1953. The M121 benefited from innovations and technology from Mercedes' larger engines such as the M186 3.0-litre and M180 2.2 liter engines. One of these innovations was a new single over head camshaft design which allowed for more power and efficiency. It was developed by a team led by Hans Scherenberg. Within this team, Karl-Heinz Goschel was one of the key engineers who developed the engine design. ==M121 variants==

M121 The M121 engine featured a single chain driven overhead camshaft layout with staggered valves operated by long and short rocker arms. The cylinder block was made from cast iron. The cylinder bore diameter for the M121 was . The three ring crankshaft was forged. The stroke of the engine was . This gave the M121 a displacement of . The engine had a compression of 8.5:1 and a single exhaust. Through this configuration, the M121 BII engine had an initial rating of at 5500 RPM and of torque at 4000 rpm. After testing of the final vehicle, the power rating was lowered to . The crankshaft was initially carried by three main bearings, raised to five in the M121 BIX variant. 190c M121 BI The M121 BI was developed for the new W110 190c introduced in 1961. It had an increase of , yet retained the same fuel consumption ( on premium gasoline). Top speed increased to from . Both performance increases were achieved despite the new model's significantly heavier bodywork required to meet new safety regulations. M121 BII The first version of the M121 to reach the market, the M121 BII was put into serial production in May of 1955 for use in the new W121 Mercedes 190SL roadster. Fitted with dual carburetors, it produced at 5700 rpm. For the 190SL, acceleration to took 14.5 seconds, and the top speed was . This made the M121 BII one of the faster engines on the road in its day. The fuel economy of the M121 BII was . M121 BIX The final version of the M121 engine was the 2.0 L M121BIX, produced from 1965 to 1968 for the new W110 Mercedes Benz 200. A increase in bore from enlarged displacement to . Compression was increased to 9.0:1, the crankshaft went from three to five bearings, and a second Solex 38PDSJ carburetor was added. Combined, power was increased to at 5200 rpm and of torque was produced at 3600 rpm. ==Applications==

The M121 engine was first employed in the 1956 Mercedes Benz W121 180 "Ponton". The subsequent 190 and 200 models featured an updated version which offered greater performance through variations in compression ratios and improved carburetor systems. Its use continued in the W110 "Fintail" 190c and 200. The M121 engine has also been used in trucks such as the Mercedes-Benz L319 introduced in 1967. 1967. Some Unimog off-road models also used the M121. ==References==