The BMW N52 was an inline six-cylinder petrol engine that was available in 2.5- and 3.0-litre capacities. Available from 2004, the N52 engine replaced the M54 engine and introduced a number of mass reduction measures – at 161 kg, it was 10 kg lighter than the M54.
Although the N52 was superseded by the N53 engine, the Australian, North American and Malaysian markets continued to receive N52-powered vehicles until the N20 engine was introduced.
Crankcase
The N52 engine had a two-piece crankcase and was the first engine for passenger vehicles to use magnesium. For the N52 engine, a special magnesium alloy (AJ62) was developed to reduce the possibility of corrosion and allow favourable machining characteristics. For the crankcase,
- The upper section of the crankcase was made from a magnesium/aluminium composite; and,
- The lower portion of the crankcase was designed as a bedplate structure and made from magnesium. Sintered steel inlays were used for the main bearings and, between the bedplate and the crankcase, a liquid sealer was injected under high pressure into a machined groove.
The crankcase contained an aluminium-silicon (AlSi17) insert – or ‘inner block’ – which was cast inseparably in a magnesium alloy. This insert provided
- threaded connections for the transmission mounting, cylinder head and crankshaft main bolts; and,
- coolant passages to prevent coolant from coming into contact with the magnesium portion of the block.
The N52 engine had Alusil cylinder bores such that iron cylinder liners were not required.
Unlike previous designs, the timing cover for the N52 engine was cast as an integral part of the engine block.
Components and DISA
The N52 engine had a cast iron crankshaft with seven main bearing journals, trapezoidal connecting rods (i.e. tapered small ends), aluminium pistons and a lightweight thermoplastic intake manifold. The N52 engine also had an electric coolant pump in place of the M54’s belt-driven pump.
The N52 engine had a three-stage Differential Intake Air Control (DISA) to improve the charge cycle, with the two DISA actuators controlled by electric motors (previously vacuum-controlled). The lower-powered, UL versions of the engine omitted DISA, had different DME programming and exhaust systems.
Cylinder head and valvetrain
The N52 engine had an Aluminium silicon (Alusil) cylinder head with a cast bridge to mount the ‘Valvetronic II’ actuator. While the N52 engine had variable intake and exhaust camshafts (BMW’s double VANOS), ‘Valvetronic II’ provided variable intake valve lift. Relative to Valvetronic I, changes for Valvetronic II included:
- Maximum lift for the intake valves increased to 9.9 mm, while minimum lift was reduced to 0.18 mm;
- A roller bearing was fitted for the intermediate lever to the eccentric shaft; and,
- Lighter valve timing gear (moved mass reduced by 13 per cent);
Furthermore, the N52 engine had four valves per cylinder that were actuated by roller cams and the cylinder head cover was cast from magnesium alloy.
Injection and ignition
The N52 engine had conventional port injection and Siemens MSV 70 engine management. For the N52B30, the compression ratio was 10.7:1 and maximum engine speed 7000 rpm.
| Engine | Capacity | Peak power | Peak torque | Models | Years |
|---|---|---|---|---|---|
| N52B25 | 2497 cc (82.0 x 78.8) |
130kW at 5800rpm | 230Nm at 3500-5000rpm | E60 523i, E61 523i, E85 Z4 2.5i |
2005-08 |
| 150kW at 6400rpm | 250Nm at 2750-3000rpm | E89 Z4 sDrive23i | 2009-11 | ||
| 160kW at 6500rpm | 250Nm at 2750-4250rpm | E90 325i, E91 325i, E92 325i, E60 525i, E61 525i, E83 X3 2.5i, E85 Z4 2.5si |
2005-10 | ||
| N52B30 | 2996 cc (85.0 x 88.0) |
160kW at 6100rpm | 270Nm at 2400-4200rpm | E82 125i, E88 125i, E84 X1 xDrive25i, E90 325i, E91 325i, E92 325i |
2007-11 |
| 190kW at 6600rpm | 300Nm at 2500-400rpm | E90 330i, E91 330i, E60 530i, E61 530i, E63 630i, E64 630i, E65 730i, E66 730i |
2004-07 | ||
| 190kW at 6600rpm | 310Nm at 2600rpm | E81 130i, E87 130i, E84 X1 xDrive28i, F25 X3 xDrive28i, E89 Z4 sDrive30i, F10 528i |
2009-11 | ||
| 195kW at 6650rpm | 315Nm at 2750rpm | E81 130i, E87 130i, E85 Z4 3.0si, E86 Z4 3.0si |
2005-09 | ||
| 200kW at 6650rpm | 315Nm at 2750rpm | E92 330i, E83 X3 3.0si, E70 X5 3.0si, E60 530i, E61 530i |
2006-10 |
Fault: N52 Hydraulic Valve Adjuster (HVA)
N52 engines produced prior to November 2008 were susceptible to ticking noises from the hydraulic valve adjuster (HVA) during cold engine starts or frequent short-distance driving. In these situations, the HVA elements may not have sufficient amounts of air-free oil. The condition usually remedies itself with a longer driving distance or operating times at full operating temperature. Vehicles produced after November 2008, however, were fitted with an improved cylinder head that overcame the problem.
