The 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 |
References
1. BMW TIS (Technical Information System)
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