BMW M20B20

BMW M20B20The BMW M20B20 is a 2.0 L (1,990 cc, 121.4 cu·in) straight-six, natural aspirated four-stroke gasoline engine, manufactured by BMW from 1976 to 1992 .

The cylinder bore is 80.0 mm (3.15 in) and the piston stroke is 66.0 mm (2.6 in). The compression ratio rating is 9.2:1, 9.9:1 or 8.8:1.

The BMW M20B20 engine produced from 122.4 PS (90 kW; 120.7 HP) at 6,000 rpm to 129.2 PS (95 kW; 127.4 HP) at 6,000 rpm of maximum output power and from 163 N·m (16.6 kg·m, 120.1 ft·lb) at 4,000 rpm to 174 N·m (17.7 kg·m, 128.2 ft·lb) at 4,000 rpm of peak torque.

The BMW M20B20 features:

  • Cast-iron cylinder block
  • Aluminum cylinder head
  • SOHC design with two valves per cylinder (12 in total)
  • Carburetor or electronic fuel injection depending on modification
  • Pressure feed lubrication system
  • Liquid-cooled cooling system

General information

Engine Specifications
Engine model M20B20
Engine type Straight-six, 4-stroke, SOHC
Displacement 2.2 L, 1,990 cm3, (121.4 cu·in)
Max. horsepower From 122.4 PS (90 kW; 120.7 HP) at 6,000 rpm
to 129.2 PS (95 kW; 127.4 HP) at 6,000 rpm
Max. torque From 163 N·m (16.6 kg·m, 120.1 ft·lb) at 4,000 rpm
to 174 N·m (17.7 kg·m, 128.2 ft·lb) at 4,000 rpm
Cooling system Liquid-cooled
Lubricating system Pressure feed
Fuel system Fuel system Solex 4A1 four-barrel carburetor
Mechanical fuel injection system (Bosch K-Jetronic)
Electronic fuel injection system (Bosch LE-Jetronic, L-Jetronic, Motronic DME1.1/DME1.3)
Starting system Electic starter 12V
Firing order: 1-5-3-6-2-4
Dimensions (L x W X H)
Dry weight 170 kg (374.8 lbs)

Cylinder Block and Head

Cylinder block
Cylinder block alloy: Cast-iron
Compression ratio: 1973-1981: 9.2:1,
1981-1987: 9.9:1,
1987-1990: 8.8:1
Cylinder bore: 80.0 mm (3.15 in)
Piston stroke: 66.0 mm (2.6 in)
Cylinder internal diameter (standard): 80.000 mm (3.1496 in)
Piston skirt outer diameter (standard): 79.980 mm (3.1488 in)
Number of piston rings (compression / oil): 2/1
Side clearance (Top): 0.040-0.080 mm (0.0016-0.0031 in)
Side clearance (Second): 0.030-0.070 mm (0.0012-0.0028 in)
Side clearance (Oil): 0.020-0.050 mm (0.0008-0.002 in)
Ring end gap (Top): 0.200-0.500 mm (0.0079-0.0197 in)
Ring end gap (Second): 0.200-0.500 mm (0.0079-0.0197 in)
Ring end gap (Oil): 0.200-0.500 mm (0.0079-0.0197 in)
Number of main bearings: 7
Crankshaft main journal diameter: 60.000 mm (2.3622 in)
Crankpin journal diameter: 45.000 mm (1.7717 in)
Crankshaft center distance: 33.0 mm (1.3 in)
Cylinder head
Cylinder head alloy: Aluminium
Valve arrangement: SOHC
Valves: 2,(12 valves in total)
Valve head diameter (INTAKE): 40.0 mm (1.5748 in)
Valve head diameter (EXHAUST): 34.0 mm (1.3386 in)
Valve steam diameter (INTAKE): 7.000 mm (0.2756 in)
Valve steam diameter (EXHAUST): 7.000 mm (0.2756 in)

Service Data

Engine speed
Idle speed: 700-780 rpm
Redline: Before 1981: 6,400 rpm
After 1981: 6,200 rpm
Compression pressure
Minimum: 10.2 kg/cm2 (9.9 bar, 145 psi) / 350 rpm
Valve clearance
Intake valve clearance: 0.25 mm (0.0098 in)
Exhaust valve clearance: 0.25 mm (0.0098 in)
OIl system
Recommended oil: SAE 5W-30, 10W-30
Oil capacity: With filter change: 4.25 L (4.5 US. qt, 3.7 Imp. qt.)
Without filter change: 4.0 L (4.2 US. qt, 3.5 Imp. qt.)
Oil change interval, km (miles): 10,000 (6,000)
Fuel system
Type: Carburetor or electronic fuel injection
Ignition system
Spark plug: Bosch: W8LCR, NGK: ZGR5A
Spark plug gap: 0.7 mm (0.0276 in)

Applications

Model Years Produced
BMW 520/6 (E12) 1976–1981
BMW 320/6 (E21) 1977–1982
BMW 520i (E28) 1981–1982
BMW 520i (E28) 1982–1984
BMW 320i (E30) 1982–1984
BMW 520i (E28) 1984–1987
BMW 320i (E30) 1984–1987
BMW 520i (E28) 1986–1987
BMW 320i (E30) 1987–1992
BMW 520i (E34) 1988–1990