BMW M20B23 Engine Specifications
The BMW M20B23 is a 2.3 liters (2,316 cc, 141.3 cubic inches)
straight-six, four-stroke cycle naturally aspirated gasoline engine from
BMW M20-family. The engine was manufactured from 1978 to 1987.
The engine features a cast-iron block and aluminum head with
a single overhead camshaft (SOHC) and two valves per cylinder (12 in
total). The cylinder bore is 80.0 mm (3.15 in) and the piston stroke is
76.8 mm (2.99 in).
The first version of the M20B23 engine uses the same head “200” and
block as the M20B20 but a longer 76.8 mm (3.02 in) stroke crank. This
engine used mechanical fuel injection system K-Jetronic, the compression
ratio is 9.5:1 and the redline is 6,400 rpm. This engine produced 143 PS
(105 KW; 141 HP) at 6,000 rpm of horsepower and 176 Nm (17.95 kgm;
129.89 ft-lb) at 4,500 rpm of peak torque.
The 1982 version used L-Jetronic, the 731 cylinder head, a compression
ratio of 9.8:1. This version produced 139 PS (102 kW; 137 HP) at 5,300
rpm of maximum horsepower and 205 Nm (20.9 kgm, 151.1 ft-lb) at 4,000
rpm of torque.
In 1984, the fuel injection system, exhaust, and camshaft were upgraded
to LE-Jetronic. Redline increased to 6,500 rpm. This engine produced 150
PS (110 kW; 147 HP) at 6,000 rpm of maximum output power and 205 Nm
(20.9 kgm, 151.1 ft-lb) at 4,000 rpm of peak torque.
The breakdown of the engine code is as follows:
M20 - Engine Family
B - Gasoline
23 - 2.3 Liter Displacement
Engine model ..................... M20B23
Cylinder layout ..................... Four stroke, Inline-6 (Straight-6)
Fuel type ..................... Gasoline
Year of production ..................... 1977-1987
Total displacement ..................... 2.3 L, 2,316 cc (141.3 cubic
inches)
Fuel system ..................... Mechanical fuel injection system
(Bosch K-Jetronic)
Electronic fuel injection system (Bosch L-Jetronic, LE-Jetronic)
Power adder ..................... None
Maximum power ..................... From 139 PS (102 kW; 137 HP) at
5,300 rpm
to 150 PS (110 kW; 147 HP) at 6,000 rpm
Maximum torque ..................... From 176 Nm (17.95 kgm; 129.89
ft-lb) at 4,500 rpm
to 205 Nm (20.9 kgm, 151.1 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)
The BMW M20B23 engine has a cast-iron cylinder block, bore is 80.0 mm
(3.15 in) and stroke is 76.8 mm (2.99 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 ..................... 9.5:1, 9.8:1
Cylinder bore ..................... 80.0 mm (3.15 in)
Piston stroke ..................... 76.8 mm (2.99 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°
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°
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)
BMW 323i (E21) ..................... 1977-1982
BMW 323i (E30) ..................... 1982-1984
BMW 323i (E30) ..................... 1984-1987
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