M20B23

M20B23 is a 2.3-liter inline-six engine from BMW's M20 family. Developed for use in the 1980s, it was employed in several mid-range BMW models, most notably in early 3-series variants such as the 323i, and reached various markets with minor tuning differences. The engine is part of BMW’s DOHC 24-valve line and shares the general M20 architecture with its larger and smaller siblings.

Technically, the M20B23 is a naturally aspirated, four-stroke, inline-six with a double overhead camshaft configuration and 24 valves. It uses a cast-iron engine block with an aluminum cylinder head and features a cam-chain drive. Fuel delivery progressed from early mechanical systems to electronic management during its production, with models commonly equipped with Bosch fuel-injection and Motronic or related control units depending on year and market. The displacement is approximately 2.3 liters, with output varying by market and emissions requirements.

Performance and characteristics vary by specification and region, but typical figures place power in the vicinity of 165–170 horsepower (roughly 123–127 kW) and peak torque around 170–180 Nm. The engine is known for a smooth delivery of torque and comparatively robust reliability when properly maintained, though older examples often require attention to cooling components, gaskets, and fuel-system wear.

Applications commonly included the E21 and early E30 3-series, where the 323i used the M20B23 engine. It was eventually superseded by larger M60/M54 derivatives in BMW’s lineup, but remains noted for its role in the late‑1980s era of the brand’s inline-six family.