BMW M20B23

BMW M20B23The 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