The BMW N53 is a naturally aspirated straight-6 petrol engine which was produced from 2006 to 2013. The N53 replaced the BMW N52 in certain markets and debuted on the post-facelift E60 5 Series. In European markets, the N53 began to replace its port injected parent, the BMW N52 in 2007. Markets such as the United States, Canada, Australia and Malaysia retained the N52 as the N53 was deemed unsuitable due to the high sulphur content of local fuel. The N52 and N53 are the last naturally aspirated straight-six engines produced by BMW, ending a history of continuous production of this engine configuration since the BMW M30 in 1968. In 2011, the N52 began to be replaced by the BMW N20 turbocharged four-cylinder engine. N53 production ceased in 2013. There is no BMW M version of the N53. The BMW N54 turbocharged straight-6 engine was produced alongside the N53.

Design

Compared with its N52 predecessor which was port-injected, the N53 uses direct injection. The direct injection system uses piezoelectric fuel injectors which inject into the combustion chamber, using a stratified lean mixture operation. The compression ratio was increased to 12.0:1 for the N53. As per the N52, the N53 has double-VANOS (variable valve timing) and a magnesium alloy block. Unlike the N52, the N53 does not have Valvetronic (variable valve lift), due to space limitations in the cylinder head. The bore of 85 mm and stroke of 88 mm are the same as the N52. Each cylinder has coil-on-plug ignition, as per the N52.

Versions

N53B25

The 2.5 L version of the N53 produces 140 kW and 235 Nm. It has a bore of 82 mm and a stroke of 78.8 mm. Applications:

N53B30 (150 kW)

A 150 kW version of the N53 was used in the pre-facelift F10 523i. Applications:

N53B30 (160 kW)

This 3.0 L version of the N53 produces 160 kW, the same figure as the 2.5 L version of its N52 predecessor. However, peak torque increased from 250 to 270 Nm. Applications:

N53B30 (190 kW)

A 190 kW version of the N53 was used in the pre-facelift F10 528i. Applications:

N53B30 (200 kW)

The most powerful version of the N53 produces 200 kW of power and 320 Nm of torque. Applications:

High-Pressure Fuel Pump failures

The N53 uses the same High-Pressure Fuel Pump (HPFP) as the BMW N54 turbocharged straight-six engine, which had HPFP failures leading to Lemon Law "buy backs" and legal action in the United States. The N53 engine was not sold in the United States, therefore the N53 engine was not involved with these actions. Failures of the N53 HPFP have been reported, although it is not known whether failure in the N53 is as common as the N54.