The BMW E12 520/6, which had a 2-liter M20B20 modification, was the first vehicle with an M20 engine. The piston stroke is 66 mm, and the cylinder diameter is 80 mm. In 1982, a BMW 520i was the first vehicle to use an M20B20 engine with a Bosch L-Jetronic injector. A Bosch Motronic catalytic converter system was used to update it in 1987.
Specifications
| Manufacturer | Munich Plant |
| Family | M20 |
| Production years | 1977-1992 |
| Cylinder block alloy | cast iron |
| Fuel system | carburetor/injector |
| Configuration | inline |
| Number of cylinders | 6 |
| Valves per cylinder | 2 |
| Piston stroke, mm | 66 |
| Cylinder bore, mm | 80 |
| Compression ratio | 9.2 9.8 9.9 9.8 8.8 |
| Displacement, cc | 1991 |
| Power output, hp | 122/6000 125/5800 126/5800 129/6000 129/6000 |
| Torque output, Nm / rpm | 160/4000 170/4000 170/4000 174/4000 174/4300 |
| Fuel type | petrol |
| Weight, kg | ~113 (dry) |
| Fuel consumption, L/100 km (for E30 320i) — city — highway — combined |
13.0 7.5 9.5 |
| Oil consumption, gr/1000 km | up to 1000 |
| Recommended engine oil | 5W-30 / 5W-40 / 10W-30 / 10W-40 / 10W-50 / 15W-50 |
| Engine oil capacity, liter | 4.25 |
| Normal engine operating temperature, °C | ~90 |
| Engine lifespan, km | ~300 000 |
Frequent problems
They encounter camshaft wear, overheating, and cylinder head integrity violations when using M20B20 engines.
Overheating can cause the cylinder head to move. At the first indication of overheating, you should assess the condition of the cooling system to prevent cylinder head failure. Air pockets are found in the system and eliminated by blowing. Evaluating the state of the radiator, pump, and thermostat is also essential.
Engine overheating can cause the cylinder head to crack. A crack frequently develops around the 4-5 cylinder; the issue can be resolved by swapping out the component.
To prevent belt breakage, valve bending, and piston breakage, the timing belt’s condition and the tensioner roller’s location should be closely observed.
A knock indicates camshaft wear, which is typical for motors with a range of 200,000 kilometers or more. A new cylinder head is installed to address the issue.