The BMW M52B25 is a 2.5 L (2,494 cc, 152.2 cu·in) straight-six, natural aspirated four-stroke gasoline engine, manufactured by BMW from 1995 to 2000.
The cylinder bore is 84.0 mm (3.31 in) and the piston stroke is 75.0 mm (2.95 in). The compression ratio rating is 10.5:1.
The M52B25 engine produced 170.0 PS (125 kW; 167.6 HP) at 5,500 rpm of maximum horsepower and 245 N·m (25 kg·m, 180.6 ft·lb) at 3,500 rpm of maximum torque.
The BMW M52B25 features:
- Cast-aluminum alloy cylinder block with Nikasil coated cylinder liners
- Aluminum cylinder head
- DOHC design with 4 valves per cylinder (24 valves in total)
- Distributorless ignition system with individual ignition coils for each cylinder ignition system
- Electronic fuel injection (EFI)
- Siemens MS 41.0, DME (Digital Motor Electronics) system
- Single VANOS (Variable Valve Timing System from BMW)
General information
| Engine Specifications | |
| Engine model | M52B25 |
| Engine type | Straight-six, 4-stroke, DOHC |
| Displacement | 2.5 L, 2,494 cm3, (152.2 cu·in) |
| Max. horsepower | 170 PS (125 kW; 167.6 HP) at 5,500 rpm |
| Max. torque | 245 N·m (25 kg·m, 180.6 ft·lb) at 3,500 rpm |
| Cooling system | Liquid-cooled |
| Lubricating system | Pressure feed |
| Ignition system | Distributorless ignition system with individual ignition coils for each cylinder |
| Fuel system | Electronic fuel injection (EFI) |
| Starting system | Starter 12V |
| Firing order: | 1-5-3-6-2-4 |
| Dry weight | 158 kg(348 lbs) |
Cylinder Block and Head
| Cylinder block | |
| Cylinder block alloy: | Aluminium |
| Compression ratio: | 10.5:1 |
| Cylinder bore: | 84.0 mm (3.31 in) |
| Piston stroke: | 75.0 mm (2.95 in) |
| Cylinder internal diameter (standard): | 84.000-84.010 mm (3.3071-3.3075 in) |
| Piston skirt outer diameter (standard): | 83.980-83.989 mm (3.3063-3.3066 in) |
| Number of piston rings (compression / oil): | 2/1 |
| Piston pin diameter: | 22.000 mm (0.8661 in) |
| Side clearance (Top): | 0.020-0.060 mm (0.0008-0.0024 in) |
| Side clearance (Second): | 0.030-0.065 mm (0.0012-0.0026 in) |
| Side clearance (Oil): | 0.020-0.060 mm (0.0008-0.0024 in) |
| Ring end gap (Top): | 0.100-0.300 mm (0.0039-0.0118 in) |
| Ring end gap (Second): | 0.200-0.400 mm (0.0079-0.0157 in) |
| Ring end gap (Oil): | 0.250-0.500 mm (0.0098-0.0197 in) |
| Number of main bearings: | 7 |
| Crankshaft main journal diameter: | 60.000 mm (2.3622 in) |
| Crankpin journal diameter: | 45.000 mm (1.7717 in) |
| Crankshaft center distance: | 37.50 mm (1.475 in) |
| Cylinder head | |
| Cylinder head alloy: | Aluminium |
| Valve arrangement: | DOHC, chain driven |
| Valves: | 4, (24 valves in total) |
| Head height: | 140.0 mm (5.5118 in) |
| Valve head diameter (INTAKE): | 33.0 mm (1.2992 in) |
| Valve head diameter (EXHAUST): | 30.5 mm (1.2008 in) |
| Valve steam diameter (INTAKE): | 6.0 mm (0.2362 in) |
| Valve steam diameter (EXHAUST): | 6.0 mm (0.2362 in) |
Service Data
| Compression pressure | |
| Minimum: | 10.0 kg/cm2 (9.9 bar, 145 psi) / 350 rpm |
| Compression differential limit between cylinders: | 1.0 kg/cm2 (1.0 bar, 15 psi) / 350 rpm |
| Oil system | |
| Lubrication system: | Pressure feed |
| Oil type: | BMW High Performance Synthetic (API SH) |
| Recommended oil: | SAE 5W-30 |
| Oil capacity: | 6.5 L (6.87 US. qt, 5.72 Imp. qt.) |
| Oil change interval, km (miles): | 5,000-10,000 (3,000-6,000) |
| Fuel system | |
| Type: | Electronic fuel injection (EFI) |
| Ignition system | |
| Type: | Distributorless ignition system with individual ignition coils for each cylinder |
| Spark plug: | Bosch: FGR7DQP, NGK: BKR6EQUP |
| Spark plug torque: | 25 N·m (2.5 kg·m, 18.4 ft·lb) |
Applications
| Model | Years Produced |
| BMW 323i (E36) | 1995-1998 |
| BMW 323ti (E36/5) | 1995-2000 |
| BMW 523i (E39) | 1995-2000 |
References
1. BMW TIS (Technical Information System)
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