BMW N52 and N53 24 Valve Six Cylinder Engines

BMW N52 engine

N52 3.0 fitted to a Z4.

Chronology

The N52 was a six cylinder 24 valve engine, it was BMW's first six to use the Valvetronic technology introduced on the N42 engine. It was produced from 2004 until 2011.

The N52 was offered in most BMW models including the E90 three series, X3, X5, Z4 and five series.

In 2007 the updated N53 was introduced with direct injection, however this was unsuitable for markets with high sulphur fuel such as North America and Australia. Those markets retained the N52, a similar strategy as was used the the N46 and N43 four cylinder engines. This new engine didn't have Valvetronic technology.

The only 2.5 litre N52 was used in the E60 523i, Z4 2.5 and Canadian E90 323i. All other cars sold as 325i, 328i, 525i, or 528i were detuned three litre models. The same is true for the N53 in the E60 523i. Various minor differences in power and torque are due to tuning of intake, exhaust and software for individual models. For example the X3's engine was more suited to a higher torque at the expense of higher horsepower design.

For the first time since 1979 and the M20 engine the BMW 320i and 520i would no longer be six cylinder cars.

BMW N52 engine

Three litre N52 in an early E90 thee series.

Design

The N52 used double VANOS and Valvetronic technologies, for a good description of Valvetronic see the N42 page. Due to space constraints in the head caused by the use of direct fuel injection into the cylinders the N53 was unable to use Valvetronic. In the four cylinder N43 engine direct injection gave fuel savings of up to 23% depending on load.

BMW used new technology to give a block with highly unusual metallurgy. The upper block was light magnesium alloy, the lower section was with a normal aluminium alloy. The bearing journals were steel and were glued to the core of the block. There were no cast iron cylinder liners, Alusil coatings were used instead. This unique technology saw a block which was 10kg lighter than the M54 is replaced. The crankshaft was cast rather than forged, a cheaper option. The valve cover was also cast from magnesium.

To save power the engines used an electric cooling pump with a flow controllable depending on engine needs. The detuned "2.5" three litre engines did not use DISA variable intake technology but the full spec. engines had a new three stage DISA system, only two stages had been used up until this point. Unusually the DME was a Siemens unit rather than Bosch Motronic.

Cars which used the detuned 3.0 engines (such as the 125i) share the exact same major components with the same part numbers as the full 3.0 motor. These cars can be re-tuned for large performance gains.

BMW N53 engine

N53 direct injection engine.

Variants

Code Size Power
bhp@rpm
Torque
lb/ft@rpm
BHP/
litre
Torque/
litre
Made Bore x
Stroke
Timing Weight
(kg)
VANOS Used in
N52 2.5detuned

2.5

3.0detuned

3.0(328i)

3.0

3.0 X3

175 @ 5800

200 @ 6400

210 @ 6100

230 @ 6600

250 @ 6600

272 @ 6650

170 @ 3500-5000

184 @ 2750

200 @ 2750-4250

232 @ 2750-4250

232 @ 2750-4250

232 @ 2750-4250

70

80

70

77

83

91

68

74

70

78

78

78

2004-07 82x78.8

82x78.8

85x88

85x88

85x88

85x88

Chain 161 VANOS+
Valvetronic
Used in E90, Z4, X3, etc.
N53 2.5

3.0detuned

3.0

3.0

190 @ 6100

204 @ 6700

218 @ 6100

272 @ 6700

173 @ 3500-5000

200 @ 1500-4250

200 @ 2400-4250

236 @ 7550-4250

76

68

72

91

69

67

67

79

2007-11

82x78.8

85x88

85x88

85x88

Chain 126 VANOS,
no Valvetronic

E90, X3, Z4, etc.

 

BMW N53 engine

N53 engine.

Problems

Not surprisingly the same coil pack and injector issues that affected the four cylinder N43 direct injection engine can affect the 2007 onwards N53 too. Basically they seem to fail quite often, this isn't a problem unique to BMW but affects a lot of GDI engines. More of a supplier issue.

Fuel pumps fail more often than normal on the N53 because they're very high pressure units. Same as above, supplier issue.

On both of these points newer parts seem to last longer, so Bosch or whoever got their act together eventually. A late model car or one that's had new parts as a fix is likely to be more reliable for this reason.

The 15,000 mile service interval is too long. Change the oil a bit sooner and the filter half way through (cheap and easy). Be wary of cheapo garages using cheapo oil, this has caused engine failures. The correct oil is expensive. Again, not just a BMW problem. Wise to do a Winns oil flush if you buy one.

The inlet valves on the N53 can build up carbon deposits which restrict the air intake and sap power. This is a common problem on many GDI cars, especially if not driven hard regularly (town cars).

If an engine sounds very clattery it can be due to air in the hydraulic valve lifters. This can happen if the oil level falls very low or the car is used for nothing but very short trips, I've seen it once. The solution is to bleed the lifters. Warm the engine up with a short drive then with the car stationary run the engine at 3500rpm for three minutes, this can be tried several times back to back if needed. Certainly worked for me.