The BMW M40 is an SOHC four-cylinder petrol engine which was produced from 1987–1994. It served as BMWs base model four-cylinder engine and was produced alongside the higher performance BMW M42 DOHC four-cylinder engine from 1989 onwards.
Compared with its M10 predecessor, the M40 uses a belt-driven camshaft, and hydraulic tappets. Like the M10, the M40 uses an iron block and an aluminium head. Fuel injection for the E30 versions is Bosch Motronic 1.3, and the E36 versions use Bosch Motronic 1.7.
Following the introduction of the BMW M43 engine in 1991, the M40 began to be phased out.
The M40B16 is a 1.596 cc 97.4 cu in version of the M40, which has a bore of 84 mm 3.3 in and a stroke of 72 mm 2.8 in. It produces 76 kW 102 bhp and 142 N⋅m 105 lb⋅ft.
- 1990–1994 E36 316i
- 1988–1994 E30 316i
- 1992–1993 Bertone Freeclimber 2
The M40B18 is a 1.796 cc 109.6 cu in version of the M40, which has a bore of 84 mm 3.3 in and a stroke of 81 mm 3.2 in. It produces 84 kW 113 bhp and 163 N⋅m 120 lb⋅ft.
- 1992–1993 E36 318i
- 1987–1994 E30 318i
- 1988–1994 E34 518i