BMW M50B25TUThe BMW M50B25TU is a 2.5 liters (2,494 cc, 152.2 cu·in) straight-six, four-stroke cycle natural aspirated gasoline engine from BMW M50-family. The engine was manufactured on Munich Plant (Munich, Germany) from 1992 to 1996.

The BMW M50B25TU engine features a cast-iron block and aluminum head with a dual overhead camshaft (DOHC) and four valves per cylinder (24 in total). The engine is equipped with an electronic fuel injection system (DME M3.3.1), VANOS (Variable Valve Timing System from BMW) for inlet camshaft, coil-on-plug ignition system, a knock sensor, and a lightweight plastic intake manifold.

The engine has an 84.0 mm (3.31 in) cylinder bore and 75.0 mm (2.95 in) piston stroke. This engine has a compression ratio rating of 10.5:1 and a redline of 6,500 rpm. The BMW M50B25TU engine produced 192 PS (141 kW; 189 HP) at 5,900 rpm of maximum output power and 245 N·m (25 kg·m, 180.6 ft·lb) at 4,200 rpm of peak torque for BMW E36 and 450 N·m (45.9 kg·m, 331.7 ft·lb) at 4,200 rpm for BMW E34.

The breakdown of the engine code is as follows:

  • M50 – Engine Family
  • B – Gasoline
  • 25 – 2.5 Liter Displacement
  • TU – Technical Update

General information

Engine Specifications
Engine codeM50B25 TU
LayoutFour stroke, Inline-6 (Straight-6)
Fuel typeGasoline
Displacement2.5 L, 2,494 cc (152.2 cu in)
Fuel systemElectronic fuel injection (MS40.1)
Power adderNone
Max. horsepower192 PS (141 kW; 189 HP) at 5,900 rpm
Max. torque E36: 245 N·m (25 kg·m, 180.6 ft·lb) at 4,200 rpm
E34: 450 N·m (45.9 kg·m, 331.7 ft·lb) at 4,200 rpm
Firing order1-5-3-6-2-4
Dimensions (L x H x W):
Weight194 kg (428 lbs)

Cylinder block

The BMW M50B25TU 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 compression ratio rating of 10.5:1. The pistons are each fitted with two compression rings and a single oil ring.

Cylinder block
Cylinder block alloyCast-iron
Compression ratio:10.5:1
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:Top0.020-0.060 mm (0.0008-0.0024 in)
Second0.030-0.065 mm (0.0012-0.0026 in)
Piston ring end gap:Top0.200-0.400 mm (0.0079-0.0157 in)
Second0.200-0.400 mm (0.0079-0.0157 in)
Oil0.400-1.400 mm (0.0157-0.0551 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°

Cylinder head

The cylinder head is made of an aluminum alloy with good cooling efficiency. The engine has a dual overhead camshaft with four valves per cylinder. Intake valves are 33.0 mm (1.30 in) in diameter and exhaust valves are 30.5 mm (1.20 in). Specifications of M50B25TU camshafts are as follows: duration is 228° for inlet and 228° for exhaust valves, valve lift is 9.0 and 9.0 mm, respectively. This motor is equipped with hydraulic lifters.

Cylinder head
Valve Arrangement:DOHC, chain drive
Valves:24 (4 valves per cylinder)
Intake/Exhaust duration:228°/228°
Valve head diameter:INTAKE33.000 mm (1.2992 in)
EXHAUST30.500 mm (1.2008 in)
Valve steam diameter:INTAKE6.000 mm (0.2362 in)
EXHAUST6.000 mm (0.2362 in)

Head tightening procedure and torque specs:

  • Step 1: 30 Nm (3.06 kg·m; 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

Compression pressure
Standard10.2 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 plugBosch: FGR7DQP, NGK: BKR6EQUP
Spark plug gap0.7 mm (0.028 in)

Vehicle applications

ModelYears Produced
BMW 325i, 325is (E36)1993-1995
BMW 525i, 525ix (E34)1992-1996
Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.

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