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BMW M20B25 Engine Specifications
The BMW M20B25 is a 2.5 liters (2,494 cc, 152.19 cu-in) straight-six, four-stroke cycle naturally aspirated gasoline engine from BMW M20-family. The engine was manufactured oNmunich Plant (Munich, Germany) since 1985 to 1991. This engine was developed on base of low displacement the M20B20 (2.0 liters). The BMW M20B25 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 84.0 mm (3.31 in) cylinder bore and 75.0 mm (2.95 in) piston stroke. It was equipped with Bosch Motronic 1.1/1.3 Adaptive fuel injection. An early version of this engine was equipped with the Bosch Motronic 1.1 engine management system and manufactured from 1985 to 1986. This engine has a compression ratio of 9.7:1 and a redline of 6,500 rpm. It produced 171 PS (126 kW; 169 HP) at 5,800 rpm of output power and 226 Nm (23.0 kgm; 166.8 ft-lb) at 4,000 rpm of torque. In 1987, the engine management was upgraded to Motronic 1.3 and the compression ratio rating was reduced to 9.3:1. This engine produced 171 PS (126 kW; 169 HP) at 5,800 rpm. The M20B25 version with catalytic converters has a compression ratio rating of 8.8:1 and produced 170 PS (125 kW; 168 HP) at 5,800 rpm of maximum horsepower and 222 Nm (22.6 kgm; 163.8 ft-lb) at 4,300 rpm of torque.
Engine code identification:
M20 - Engine Family
B - Gasoline
25 - 2.5 Liter Displacement
| GENERAL TECHNICAL DATA |
Engine model ..................... M20B25
Cylinder layout ..................... Four stroke, Inline-6 (Straight-6)
Fuel type ..................... Gasoline
Year of production ..................... 1985-1991
Total displacement ..................... 2.5 L, 2,494 cc (152.19 cubic
inches)
Fuel system ..................... Fuel injection system
Power adder ..................... None
Maximum power ..................... 170 PS (125 KW; 168 HP) at 5,800 rpm
171 PS (126 KW; 169 HP) at 5,800 rpm
Maximum torque ..................... 215 Nm (21.9 kgm; 158.7 ft-lb) at
4,000 rpm
226 Nm (23.0 kgm; 166.8 ft-lb) at 4,000 rpm
222 Nm (22.6 kgm; 163.8 ft-lb) at 4,300 rpm
Firing order ..................... 1-5-3-6-2-4
Dimensions (L x H x W) ..................... -
Weight ..................... 175 kg(385 lbs)
| CYLINDER BLOCK |
The BMW M20B25 engine has a cast-iron cylinder block, bore is 84.0 mm
(3.31 in) and stroke is 75.0 mm (2.95 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 ..................... 9.7:1, 9.3:1, 8.3:1
Cylinder bore ..................... 84.0 mm (3.31 in)
Piston stroke ..................... 75.0 mm (2.95 in)
Number of piston rings (compression / oil) ..................... 2 / 1
Number of main bearings ..................... 7
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. Cylinder head number is 885. The engine has single overhead
camshaft with intake and exhaust duration of 256° The camshaft is driven
by a timing belt.
Intake valves are 42.0 mm (1.65 in) in diameter and exhaust valves are
36.0 mm (1.42 in), valve lift are 10.1 mm (0.397 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 ..................... SOHV, belt drive
Valves ..................... 12 (2 valves per cylinder)
Intake/Exhaust duration ..................... 256° / 256°
Valve head diameter ..................... INTAKE .....................
42.0 mm (1.65 in)
EXHAUST ..................... 36.0 mm (1.42 in)
Valve lift ..................... INTAKE ..................... 10.1 mm
(0.397 in)
EXHAUST ..................... 10.1 mm (0.397 in)
Head tightening procedure and torque specs:
Hex-Head
Step 1: 40.0 Nm; 4.1 kgm; 29.5 ft-lb
Step 2: 60.0 Nm (6.1 kgm; 44.3 ft-lb)
Step 2: Turn all bolts 25°
Torx Head
Step 1: 30.0 Nm (3.1 kgm; 22.1 ft-lb)
Step 2: Turn all bolts 90°
Step 2: Turn all another 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 325i (E30) ..................... 1985-1993
BMW 525i (E34) ..................... 1989-1990
BMW Z1 ..................... 1988-1991
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| Engines Technical Specifications |