The N52 was the first water-cooled engine to use magnesium/aluminium composite construction in the engine block.[1] It was also listed as one of Ward's 10 Best Engines in 2006 and 2007.[2][3][4]
In European markets, the N52 began to be phased out following the release of the BMW N53 in 2007. However, in markets such as the United States, Canada, Australia and Malaysia, the N53 was deemed unsuitable due to the high levels of sulfur in the fuel.[5] From the year 2011, the N52 began to be replaced by the BMW N20 turbocharged four-cylinder engine until production of the N52 finished in 2015.[6]
Unlike its predecessors, there is no BMW M version of the N52.
Design
Rear of N52, with Valvetronic visible
Compared with its M54 predecessor, the N52 features Valvetronic (variable valve lift),[7] a lighter block due to the use of a magnesium alloy[8] and an electric water pump (replacing the belt-driven water pump)[9][10] and a variable output oil pump.[11] The redline was increased from 6,500 rpm to 7,000 rpm, except for N52B25 (130 kW).[12]
The N52 engine block is made from a combination of magnesium and aluminium.[12] Magnesium is lighter than aluminium, however it has a greater risk of corrosion from water and may creep under load at high temperatures; this makes traditional magnesium alloys not suited for withstanding the high loads to which an engine block is exposed. Therefore, BMW used a magnesium alloy for the crankcase shell, with an aluminum 'inner block' to overcome the limitations of magnesium alloys.[11][15] The cylinder liners are made of Alusil[16] and a hollow camshaft is used to reduce weight.[11]
N52 shown from the intake sideFront of the N52Front of the N52, with VANOS units visibleExhaust side of the N52Cutaway view of the N52 intake side, showing the cylinders
The 3.0 L (183 cu in) models of the N52 have a bore of 85 mm (3.35 in), a stroke of 88 mm (3.46 in) and a compression ratio of 10.7:1. Variations in power output are often due to different intake manifolds and variations of engine management software.[19]
The N51 engine is a SULEV version of the N52 that was sold in parts of the United States that had SULEV legislation.[25] Differences to the N52 versions include a variable-length intake manifold ("DISA") with three stages instead of one, and a compression ratio lowered from 10.7:1 to 10.0:1.[26]
Recalls
In 2017, BMW recalled 740,000 six-cylinder models due to reports of the heater for the crankcase ventilation valve short-circuiting and causing a fire.[27]
^"BMW N51 vs N52 Engine Differences". www.tuningforbmws.com. Archived from the original on 16 August 2018. Retrieved 17 August 2019. Note: Web page still active, but image links are broken in the current version
