BMW M50B25 (2.5 L, DOHC) Engine Specs, Review & Service Data

BMW M50B25 Engine Specs

The BMW M50B25 is a 2.5 liters (152.2 cu·in, 2,494 cc) straight-six, four-stroke cycle natural aspirated gasoline engine from BMW M50-family. The engine was manufactured from 1990 to 1992.

The BMW M50B25 engine is fitted with an electronic fuel injection system (DME M3.1), a knock sensor, a coil-on-plug ignition system, and a lightweight plastic intake manifold.

The BMW M50B25 engine delivered 192 PS (141 kW; 189 Horsepower) at 6,000 rpm of maximum output power and 245 N·m (25 kg·m, 180.6 ft·lb) at 4,700 rpm of peak torque.

The BMW M50B25 engine features a dual overhead camshaft (DOHC), a cast-iron block and aluminum head, and four valves per cylinder (24 in total). 

BMW M50B25 engine has an 84.0 mm (3.31 in) cylinder bore and 75.0 mm (2.95 in) piston stroke. This BMW M50B25 engine has a compression ratio rating of 10.0:1 and a redline of 6,500 rpm. 

The breakdown of the BMW M50B25 engine code is as follows:

  • M50 – Engine Family
  • B – Gasoline
  • 25 – 2.5 Liter Displacement

BMW M50B25 Engine Specs

BMW M50B25 (2.5 L, DOHC) Engine Specs

Engine Specifications

Engine code M50B25
Layout Four stroke, Inline-6 (Straight-6)
Fuel type Gasoline
Production 1990-1992
Displacement 2.5 L, 2,494 cc (152.2 cu in)
Fuel system Electronic fuel injection (MS40.1)
Power adder None
Max. horsepower 192 PS (141 kW; 189 HP) at 6,000 rpm
Max. torque 245 N·m (25 kg·m, 180.6 ft·lb) at 4,700 rpm
Firing order 1-5-3-6-2-4
Dimensions (L x H x W):
Weight 194 kg (428 lbs)

Cylinder head

Valve Arrangement: DOHC, chain drive
Valves: 24 (4 valves per cylinder)
Intake/Exhaust duration: 240°/228°
Valve head diameter: INTAKE 33.000 mm (1.2992 in)
EXHAUST 30.500 mm (1.2008 in)
Valve steam diameter: INTAKE 7.000 mm (0.2756 in)
EXHAUST 7.000 mm (0.2756 in)

Cylinder block

Cylinder block alloy Cast-iron
Compression ratio: 10.0:1
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
Cylinder inner diameter (standard): 84.000-84.014 mm (3.3071-3.3076 in)
Piston skirt diameter (standard): 83.980 mm (3.3063 in)
Piston ring side clearance: Top 0.020-0.052 mm (0.0008-0.002 in)
Second 0.020-0.052 mm (0.0008-0.002 in)
Oil 0.020-0.055 mm (0.0008-0.0022 in)
Piston ring end gap: Top 0.200-0.400 mm (0.0079-0.0157 in)
Second 0.200-0.400 mm (0.0079-0.0157 in)
Oil 0.200-0.450 mm (0.0079-0.0177 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:

  • Step 1: 20 Nm; 2.04 kg·m; 14.76 ft·lb
  • Step 2: Tighten bolts at the angle of 50°

After securing bearing cap bolts, make sure crankshaft turns smoothly by hand.

Connecting rod bearing bolts

  • Step 1: 5 Nm; 0.51 kg·m; 3.69 ft·lb
  • Step 2: 20 Nm; 2.04 kg·m; 14.76 ft·lb
  • Step 3: Tighten bolts at the angle of 70°

Maintenance Data

Compression pressure
Standard 10.2 kg/cm2 (9.9 bar, 145 psi) / 350 rpm
Oil system
Recommended engine oil 5W-30, 5W-40, 10W-30, 10W-40
Oil type API
Engine oil capacity (Refill capacity) With filter change: 5.75 L (6.08 US. qt, 5.06 Imp. qt.)
Oil change interval, km (miles) 10,000 (6,000)
Ignition system
Spark plug Bosch: FGR7DQP, NGK: BKR6EQUP
Spark plug gap 0.7 mm (0.028 in)

Vehicle Applications

Model Years Produced
BMW 525i, 525ix (E34) 1990-1992
BMW 325i, 325is (E36) 1991-1992

Also Check:

Final Words

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