M20
M20B25 2.5 litre 12 Valve Engine
The M20 is an straight-6 piston engine of BMW.
The 12-valve, belt driven SOHC design was introduced in the 1977 BMW 520/6 and 320/6. With displacements ranging from 2.0 to 2.7 liters, it was the "little brother" to the larger BMW M30 engine. It was intended to replace the larger displacement 4-cylinder motors and was born out of BMW's conviction that a small six had more development potential than a large four (i.e. 2 liters+)
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 sometime in 1993. By that time, the newer twin-cam M50 engines with 4 valves per cylinder had already been used in the E36 and E34 for a couple of years.
Three different head castings were used over the engine's production run. The earliest was #1264200 aka the "200". These were used in all e21 320/6 and 323i and e12 520/6 engines and later in the e28 and e30 eta engines (eta = "Power With Economy"). The next version was #1277731 aka the "731". This head was the same as the 200 but featured larger intake ports. The final version was #1705885 or "885" introduced in the 325i. Ports were further enlarged, valves were larger and the combustion chamber was redesigned to improve flow and thermodynamic efficiency.
As the BMW M21, it became a diesel engine that was also available with a turbocharger.
Engine Specs
| Engine | Displacement | Power | Torque | Redline | Year |
|---|---|---|---|---|---|
| M20B20 | 2.0 L (1990 cc/121 in³) | 92 kW (123 hp) @ 5800 | 165 N·m (121 ft·lbf) @ 4000 | 1981 | |
| 92 kW (123 hp) @ 5800 | 170 N·m (125 ft·lbf) @ 4000 | 1981 | |||
| 95 kW (127 hp) @ 6000 | 174 N·m (128 ft·lbf) @ 4000 | 6200 | 1985 | ||
| 95 kW (129 hp) @ 6000 | 164 N·m (120 ft·lbf) @ 4300 | 6200 | 1986 | ||
| M20B23 | 2.3 L (2316 cc/141 in³) | 102 kW (143 hp) @ 5300 | 205 N·m (151 ft·lbf) @ 4000 | 6500 | 1982 |
| 110 kW (139-150 hp) @ 6000 | 205 N·m (151 ft·lbf) @ 4000 | 6500 | 1983 | ||
| M20B25 | 2.5 L (2494 cc/152 in³) | 126 kW (168 hp) @ 5800 | 226 N·m (166 ft·lbf) @ 4000 | 6700 | 1985 |
| 120 kW (170 hp) @ 5800 | 215 N·m (158 ft·lbf) @ 4000 | 6700 | 1985 | ||
| 125 kW (168 hp) @ 5800 | 222 N·m (163 ft·lbf) @ 4300 | 6700 | 1987 | ||
| M20B27 | 2.7 L (2693 cc/164 in³) | 92 kW (121 hp) @ 4250 | 240 N·m (177 ft·lbf) @ 3250 | 4500 | 1983 |
| 95 kW (127 hp) @ 4250 | 240 N·m (177 ft·lbf) @ 3250 | 4500 | 1986 | ||
| 90 kW (120 hp) @ 4250 | 230 N·m (169 ft·lbf) @ 3250 | 4500 | 1985 | ||
| 95 kW (127 hp) @ 4800 | 230 N·m (169 ft·lbf) @ 3200 | 4500 | 1986 |
Other variations
- M20b20
- M20b23
