The BMW M20B23 is a 2.3 L (2,316 cc, 141.3 cu·in) straight-six, natural aspirated four-stroke gasoline engine, manufactured by BMW from 1977 to 1987.
The cylinder bore is 80.0 mm (3.15 in) and the piston stroke is 76,8 mm (2.99 in). The compression ratio rating is 9.8:1 or 9.5:1 depending on the year.
The M20B23 engine produced from 138.7 PS (102 kW; 136.8 HP) at 5,300 rpm to 149.6 PS (110 kW; 147.5 HP) at 6,000 rpm of maximum horsepower and from 176 N·m (17.9 kg·m, 129.7 ft·lb) at 4,500 rpm to 205 N·m (20.9 kg·m, 151.1 ft·lb) at 4,000 rpm of maximum torque.
The BMW M20B23 features:
- Cast-iron block and Aluminum head
- SOHC design
- K-Jetronic, L-Jetronic or LE-Jetronic fuel system
- Pressurazed lubrication system
- Liquid-cooled cooling system
General information
| Engine Specifications | |
| Engine model | M20B23 |
| Engine type | Straight-six, 4-stroke, SOHC |
| Displacement | 2.3 L, 2,316 cm3, (141.3 cu·in) |
| Max. horsepower | From 138.7 PS (102 kW; 136.8 HP) at 5,300 rpm to 149.6 PS (110 kW; 147.5 HP) at 6,000 rpm |
| Max. torque | From 176 N·m (17.9 kg·m, 129.7 ft·lb) at 4,500 rpm to 205 N·m (20.9 kg·m, 151.1 ft·lb) at 4,000 rpm |
| Cooling system | Forced air |
| Lubricating system | Pressurazed |
| Fuel system | 1977-1982: K-Jetronic 1982-1984: L-Jetronic 1984-1987: LE-Jetronic |
| Starting system | Electric starter |
| 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: | Before 1982: 9.5:1 After 1982: 9.8:1 |
| Cylinder bore: | 80.0 mm (3.15 in) |
| Piston stroke: | 76.8 mm (2.99 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: | 38 mm (1.495 in) |
| Cylinder head | |
| Cylinder head alloy: | Aluminium |
| Valve arrangement: | SOHC, belt driven |
| 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: | 750-800 rpm |
| Redline: | 6,400-6,500 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) |
| Ignition system | |
| Spark plug: | Bosch: W8LCR, NGK: ZGR5A |
| Spark plug gap: | 0.7 mm (0.0276 in) |
Applications
| Model | Years Produced |
| BMW 323i (E21) | 1977–1982 |
| BMW 323i (E30) | 1982–1984 |
| BMW 323i (E30) | 1984–1987 |
References
1. BMW TIS (Technical Information System)
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