BMW M50B20

The BMW M50B20 is a 2.0 liters (1,990 cc, 121.4 cu·in) straight-six, four-stroke cycle natural aspirated gasoline engine from BMW M50-family. The engine was manufactured from 1990 to 1992.

The BMW M50B20 engine features a cast-iron block and aluminum head with a dual overhead camshaft (DOHC) and four valves per cylinder (24 in total). The engine is equipped with an electronic fuel injection system (DME M3.1), coil-on-plug ignition, a knock sensor, and a lightweight plastic intake manifold.

The engine has an 80.0 mm (3.15 in) cylinder bore and 66.0 mm (2.6 in) piston stroke. This engine has a compression ratio rating of 10.5:1 and a redline of 6,500 rpm. The BMW M50B20 engine produced 145 PS (110 kW; 147 HP) at 6,000 rpm of maximum output power and 190 N·m (19.4 kg·m, 140 ft·lb) at 4,700 rpm of peak torque.

The breakdown of the engine code is as follows:

• M50 – Engine Family
• B – Gasoline
• 20 – 2.0 Liter Displacement

General information

Cylinder block

The BMW M50B20 engine has a cast-iron cylinder block, bore is 80.0 mm (3.15 in) and stroke is 66.0 mm (2.6 in). The pistons are each fitted with two compression rings and a single oil ring.

Main bearing cap bolts tightening procedure and torque specs:

• Step 1: 20 Nm; 2.04 kg·m; 14.76 ft·lb
• Step 2: Tighten bolts at the angle of 50°

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing bolts

• Step 1: 5 Nm; 0.51 kg·m; 3.69 ft·lb
• Step 2: 20 Nm; 2.04 kg·m; 14.76 ft·lb
• Step 3: Tighten bolts at the angle of 70°

Cylinder head

The cylinder head is made of an aluminum alloy with good cooling efficiency. The engine has a dual overhead camshaft with four valves per cylinder. Intake valves are 30.0 mm (1.18 in) in diameter and exhaust valves are 27.0 mm (1.06 in). Specifications of M50B20 camshafts are as follows: duration is 240° for inlet and 228° for exhaust valves, valve lift is 9.7 and 8.8 mm, respectively. This motor is equipped with hydraulic lifters.

Head tightening procedure and torque specs:

• Step 1: 30 Nm (3.06 kg·m; 22.14 ft·lb)
• Step 2: Tighten bolts at the angle of 90°
• Step 3: Once again, tighten bolts at the angle of 90°

Maintenance data

Vehicle applications

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