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BMW M20B20 Engine Specifications
The BMW M20B20 is a 2.0 liters (1,990 cc, 121.4 cubic inches) straight-six, four-stroke cycle naturally aspirated gasoline engine from BMW M20-family. The engine was manufactured from 1976 to 1992. The engine features a cast-iron block and aluminum head with a single overhead camshaft (SOHC) and two valves per cylinder (12 in total). It has an 80.0 mm (3.15 in) cylinder bore and 66.0 mm (2.6 in) piston stroke. An early version of this engine was equipped with the Solex 4A1 four-barrel carburetor. This engine has a compression ratio of 9.2:1 and a redline of 6,400 rpm. It produced 122 PS (90 kW; 121 HP) at 6,000 rpm of horsepower and 163 Nm (16.6 kgm, 120.1 ft-lb) at 4,000 rpm of peak torque. In 1981, the engine began to use a mechanical fuel injection system and the Bosch K-Jetronic engine management system. The compression ratio rating was increased to 9.9:1. In September 1982 the fuel system was updated to electronic fuel injection (LE-Jetronic) with a redline of 6,200 rpm. In 1987, the M20B20 was revised with the addition of the Bosch Motronic engine management and catalytic converter. It has a compression ratio rating of 8.8:1. This engine produced 130 PS (95 kW; 127 HP) at 6,000 rpm of horsepower and 174 Nm (17.7 kgm, 128.2 ft-lb) at 4,000 rpm of peak torque.
Engine code identification: M20 - Engine Family B - Gasoline 20 - 2.0 Liter Displacement
| GENERAL TECHNICAL DATA |
Engine model ..................... M20B20
Cylinder layout ..................... Four stroke, Inline-6 (Straight-6)
Fuel type ..................... Gasoline
Year of production ..................... 1976-1992
Total displacement ..................... 2.0 L, 1,990 cc (121.4 cubic
inches)
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)
Power adder ..................... None
Maximum power ..................... From 122 PS (90 kW; 121 HP) at 6,000
rpm
to 129 PS (95 kW; 127 HP) at 6,000 rpm
Maximum torque ..................... From 163 Nm (16.6 kgm, 120.1 ft-lb)
at 4,000 rpm
to 174 Nm (17.7 kgm, 128.2 ft-lb) at 4,000 rpm
Firing order ..................... 1-5-3-6-2-4
Dimensions (L x H x W) ..................... -
Weight ..................... 170 kg (374.8 lbs)
| CYLINDER BLOCK |
The BMW M20B20 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 cylinder block, a
monoblock specially cast structure. The pistons are each fitted with two
compression rings and a single oil ring.
Cylinder block alloy ..................... Cast iron
Compression ratio ..................... 9.2:1, 9.9:1, 8.8:1
Cylinder bore ..................... 80.0 mm (3.15 in)
Piston stroke ..................... 66.0 mm (2.6 in)
Number of piston rings (compression / oil) ..................... 2 / 1
Number of main bearings ..................... 7
Cylinder inner diameter (standard) ..................... 80.000 mm
(3.1496 in)
Piston skirt diameter (standard) ..................... 79.980 mm (3.1488
in)
Piston ring side clearance ..................... Top
..................... 0.040-0.080 mm (0.0016-0.0031 in)
Second ..................... 0.030-0.070 mm (0.0012-0.0028 in)
Oil ..................... 0.020-0.050 mm (0.0008-0.002 in)
Piston ring end gap ..................... Top .....................
0.200-0.500 mm (0.0079-0.0197 in)
Second ..................... 0.200-0.500 mm (0.0079-0.0197 in)
Oil ..................... 0.200-0.500 mm (0.0079-0.0197 in)
Crankshaft journal diameter ..................... 60.000 mm (2.3622 in)
Crankpin diameter ..................... 45.000 mm (1.7717 in)
Main bearing cap bolts tightening procedure and torque specs:
60 Nm (6.12 kgm; 44.28 ft-lb)
After securing bearing cap bolts, make sure crankshaft turns smoothly by
hand.
Connecting rod bearing bolts
Step 1: 5 Nm; 0.51 kgm; 3.69 ft-lb
Step 2: 20 Nm; 2.04 kgm; 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 single overhead camshaft with two valves
per cylinder. The camshaft is driven by a timing belt.
Intake valves are 40.0 mm (1.57 in) in diameter and exhaust valves are
34.0 mm (1.34 in). The valves are opened and closed by rocker arms.
These rocker arms perform a dual function of cam follower valve
adjuster, as one end contains the eccentric and the adjustment nut. The
rocker arms pivot around rocker arm shafts.
Valve Arrangement ..................... SOHC, belt drive
Valves ..................... 12 (2 valves per cylinder)
Intake/Exhaust duration ..................... -
Valve head diameter ..................... INTAKE .....................
40.0 mm (1.5748 in)
EXHAUST ..................... 34.0 mm (1.3386 in)
Valve steam diameter ..................... INTAKE .....................
7.0 mm (0.2756 in)
EXHAUST ..................... 7.0 mm (0.2756 in)
Head tightening procedure and torque specs:
Step 1: 30 Nm (3.06 kgm; 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 |
Valve clearance
Intake valve ..................... 0.25 mm (0.010 in)
Exhaust valve ..................... 0.25 mm (0.010 in)
Compression pressure
Minimum ..................... 10.2 kg/cm2 (9.9 bar, 145 psi) / 350 rpm
Oil system
Recommended engine oil ..................... 5W-30, 5W-40, 10W-30,
10W-40, 10W-50, 15W-40, 15W-50
Oil type API ..................... -
Engine oil capacity (Refill capacity) ..................... With filter
change 4.25 l
Without filter change 4.0 l
Oil change interval, km (miles) ..................... 10,000 (6,000)
Ignition system
Spark plug ..................... Bosch: W8LCR, NGK: ZGR5A
Spark plug gap ..................... 0.7 mm (0.028 in)
| VEHICLE APPLICATIONS |
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
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