The BMW N52B25 is a 2.5 liters (2,497 cc, 152.4 cu·in) straight-six, liquid-cooled, four-stroke cycle natural aspirated gasoline engine from BMW N52-family. The engine was manufactured on Munich Plant (Munich, Germany) from 2005 to 2011.
The BMW N52B25 engine features a magnesium-aluminum alloy cylinder block. The aluminum cylinder head uses chain-driven double overhead camshafts (DOHC) and four valves per cylinder (24 valves in total). It is equipped with a Siemens MSV70 engine management system, double VANOS (Variable Valve Timing System from BMW), Valvetronic (Variable Valve Lift system), electronic controlled throttle, variable-length intake manifold (called “DISA” by BMW), a distributorless ignition system with individual ignition coils for each cylinder.
Cylinder bore and piston stroke are 82.0 mm (3.23 in) and 79.0 mm (3.11 in), respectively. The compression ratio rating is 11.0:1.
The N52B25 engine had three modifications:
- N52B25O1 this modification was manufactured from 2005 to 2008, and used for BMW models with 25i index. This engine produced 218 PS (160 kW; 215 HP) at 6,500 rpm of horsepower and 250 N·m (25.5 kg·m, 184.3 ft·lb) at 2,750-3,000 rpm of torque.
- N52B25U1 this version with decreased level of HP was manufactured from 2005 to 2010 and used for BMW models with 23i index. This version produced 177 PS (130 kW; 174 HP) at 6,500 rpm of output power and 230 N·m (23.5 kg·m, 169.5 ft·lb) at 3,500-5,000 rpm of torque.
- N52B25 this version was equipped with another intake manifoldand was was manufactured from 2009 to 2011. This version produced 204 PS (150 kW; 201 HP) at 6,400 rpm of output power and 250 N·m (25.5 kg·m, 184.3 ft·lb) at 2,750-4,250 rpm of torque, and used for BMW models with 23i index.
The breakdown of the engine code is as follows:
- N – New engine generation
- 5 – Six-cylinder
- 2 – Valvetronic
- B – Gasoline
- 25 – 2.5 Liter Displacement
General information
| Engine Specifications | |
| Engine code | N52B25 |
| Layout | Four stroke, Inline-6 (Straight-6) |
| Fuel type | Gasoline |
| Production | 2005-2011 |
| Displacement | 2.5 L, 2,494 cc (152.2 cu in) |
| Fuel system | Fuel injection system |
| Power adder | None |
| Max. horsepower | N52B25O1: 218 PS (160 kW; 215 HP) at 6,500 rpm N52B25U1: 177 PS (130 kW; 174 HP) at 6,500 rpm N52B25: 204 PS (150 kW; 201 HP) at 6,400 rpm |
| Max. torque | N52B25O1: 250 N·m (25.5 kg·m, 184.3 ft·lb) at 2,750-3,000 rpm N52B25U1: 230 N·m (23.5 kg·m, 169.5 ft·lb) at 3,500-5,000 rpm N52B25: 250 N·m (25.5 kg·m, 184.3 ft·lb) at 2,750-4,250 rpm |
| Firing order | 1-5-3-6-2-4 |
| Dimensions (L x H x W): | – |
| Weight | 161 kg (353 lbs) |
Cylinder block
The N52B25 engine used a magnesium-aluminum alloy cylinder block, Alusil cylinder bores, cast iron crankshaft with seven main bearing journals, trapezoidal connecting rods (i.e. tapered small ends), aluminum pistons, and a lightweight thermoplastic intake manifold.
The cylinder bore is 82.0 mm (3.23 in) and the piston stroke is 79.0 mm (3.11 in). The compression ratio rating is 11.0:1.
| Cylinder block | ||
| Cylinder block alloy | Magnesium-aluminum alloy | |
| Compression ratio: | 11.0:1 | |
| Cylinder bore: | 82.0 mm (3.23 in) | |
| Piston stroke: | 79.0 mm (3.11 in) | |
| Number of piston rings (compression / oil): | 2 / 1 | |
| Number of main bearings: | 7 | |
| Cylinder inner diameter (standard): | 82.000-82.014 mm (3.2283-3.2289 in) | |
| Piston skirt diameter (standard): | 81.985 mm (3.2277 in) | |
| Piston pin outer diameter: | – | |
| Piston ring side clearance: | Top | 0.020-0.060 mm (0.0008-0.0024 in) |
| Second | 0.020-0.060 mm (0.0008-0.0024 in) | |
| Piston ring end gap: | Top | 0.180-0.330 mm (0.0071-0.013 in) |
| Second | 0.300-0.500 mm (0.0118-0.0197 in) | |
| Crankshaft journal diameter: | 56.000 mm (2.2047 in) | |
| Crankpin diameter: | 50.000 mm (1.9685 in) | |
Cylinder head
The cylinder head is made of Aluminium silicon (Alusil). The N52B25 engine uses chain-driven double overhead camshafts and four valves per cylinder. The N52B25 engine is equipped with BMW’s double VANOS on intake and exhaust camshafts and Valvetronic II system.
Standart head height is 112.0 mm (4.40 in). Intake valves are 32.2 mm (1.27 in) in diameter and exhaust valves are 27.0 mm (1.063 in). Valve clearance is set by self-adjusting (zero-lash) hydraulic lifters for reduced valve noise and the elimination of routine valve adjustment.
| Cylinder head | ||
| Cylinder head alloy | Aluminum | |
| Valve Arrangement: | DOHC, chain driven | |
| Valves: | 24 (4 valves per cylinder) | |
| Head height: | 112.0 mm (4.4094 in) | |
| Valve head diameter: | INTAKE | 32.2 mm (1.2677 in) |
| EXHAUST | 27.0 mm (1.063 in) | |
| Valve steam diameter: | INTAKE | 5.000 mm (0.1969 in) |
| EXHAUST | 6.000 mm (0.2362 in) | |
Maintenance 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 | |
| Recommended engine oil | 0W-30, 0W-40, 5W-40 |
| Oil type | BMW LL-01 |
| Engine oil capacity (Refill 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) |
| Ignition system | |
| Spark plug | NGK 5987 PLZFR6A-11S or Bosch FR7NPP332 |
| Spark plug gap: | 1.0 mm (0.0394 in) |
| Spark plug torque: | 23 N·m (2.3 kg·m, 17 ft·lb) |
Vehicle applications
| Model | Years Produced |
| N52B25U1 (130 kW) | |
| BMW 323i (E90) – Canada | 2006 |
| BMW 523i (E60/E61) | 2004-2007 |
| BMW Z4 2.5i (E85) | 2006-2008 |
| N52B25 (150 kW) | |
| BMW 323i (E90) Canada | 2007-2011 |
| BMW 523i (F10) | 2010-2011 |
| BMW Z4 sDrive23i (E89) | 2009-2011 |
| N52B25O1 (160 kW) | |
| BMW X3 2.5si, xDrive25i (E83) | 2005-2010 |
| BMW 525i, 525xi (E60/E61) – except U.S. and Canada | 2005-2010 |
| BMW 325i, 325xi (E90/E91/E92/E93) – except U.S. and Canada | 2005-2011 |
| BMW Z4 2.5si (E85) | 2005-2008 |
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