The BMW M20 is a SOHC straight-six petrol engine which was produced from 1977 to 1993. It was introduced eight years after the larger BMW M30 straight-six engine, which remained in production alongside the M20. The first cars to use the M20 were the E12 5 Series and the E21 3 Series. The initial M20 model had a displacement of , with later versions having displacements of up to . The M20 began to be phased out following the introduction of the M50 engine in 1990. The final M20 engines were fitted to the E30 3 Series wagon (estate) and convertible model built in April 1993. The M20 was the basis for the BMW M21 diesel engine. It is also loosely related to the BMW M70 V12 petrol engine. History By the 1970s, BMW felt the need for a six-cylinder engine smaller than the BMW M30, to use in the 3 Series and 5 Series. The resulting M20 had a displacement of , BMW's smallest straight-six engine of its day. BMW presented the M20 engine at the 1977 IAA as a 90 kW 2.0-litre Solex 4A1 carburetted version, and as a 105 kW 2.3-litre K-Jetronic multi-point injected version. Later versions had displacements up to . The M20 was used in the E12 5 Series, E21 3 Series, E28 5 Series, E30 3 Series and E34 5 Series. Early versions of the M20 were sometimes referred to as the "M60", although the M60 designation has since been re-used for a V8 engine produced from 1992 to 1996. Design As per the M30, the M20 has an iron block, aluminium head and a SOHC valvetrain with 2 valves per cylinder. It has a traditional rocker arm design and no hydraulic tappets. The major differences to the M30 are: A timing belt rather than a timing chain Bore spacing of , rather than Slant angle of 20 degrees, compared with 30 degrees for the M30. Models M20B20 The first models to use the M20 were the E12 520/6 and the E21 320/6, which used a version known as the M20B20VE or M60/2. This engine uses a bore of and a stroke of . A Solex 4A1 four-barrel carburetor was used in the M20B20VE ("VE" is for vergaser- "carburettor" in German), and it has a compression ratio of 9.2:1 and a redline of 6,400 rpm. The M20 first became fuel-injected in 1981, with Bosch