BMW M20

BMW M20 engine
Overview
Manufacturer	BMW
Production	1977–1993
Combustion chamber
Configuration	Straight-six engine
Displacement	2.0 L (1991 cc; 121.5 cu in) 2.3 L (2316 cc; 141.3 cu in) 2.5 L (2494 cc; 152.2 cu in) 2.7 L (2693 cc; 164.3 cu in)
Cylinder bore	80 mm (3.1 in) (2.0, 2.3) 84 mm (3.3 in) (2.5, 2.7)
Piston stroke	66 mm (2.6 in) (2.0) 75 mm (3.0 in) (2.5) 76.8 mm (3.0 in) (2.3) 81 mm (3.2 in) (2.7)
Chronology
Predecessor	None
Successor	BMW M50

The BMW M20 is a straight-six SOHC piston engine produced from 1977-1993. It was released in 1977 in the E12 520/6 and E21 320/6 and began to be phased out following the introduction of the M50 engine in 1990.

Like the larger capacity M30 engine from which it is derived, the M20 has a SOHC and 2 valves per cylinder. While the M30 camshaft is chain driven, the M20 camshaft and auxiliary shaft are driven by a timing belt. Initially released with a carburetor, later models used Bosch fuel injection.

With displacements ranging from 1991 cc to 2693 cc, it was the "little brother" to the larger BMW M30. It has 91 mm (3.6 in) bore-spacing instead of the 100 mm (3.9 in) of the M30 six-cylinder and the M10 four-cylinder engines.

Powering the E21 and E30 3-Series, as well as E12, E28 and E34 5 Series cars, it was produced for nearly two decades, with the last examples powering the E30 325i touring built until April 1993.

Early versions of the M20 were sometimes referred to as the "M60", although the M60 code has since been used by BMW for a V8 engine produced from 1992-1996.

The M20 was the basis for the M21 diesel engine and the M70 V12 engine.

The first models to use the M20 were the E12 520/6 and the E21 320/6, which used the 1991 cc M20B20. This engine uses a bore of 80 mm (3.1 in) and a stroke of 66 mm (2.6 in). Fuel was supplied by a Solex 4A1 four-barrel carburetor.

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