BMW N53

The BMW N53 is a straight 6 DOHC piston engine which was produced from 2006 to 2011. It is the final naturally aspirated straight-6 engine produced by BMW, ending a history of continuous production of this engine configuration since 1968. The N53 released in 2006 in the facelifted E60/E61 523i and 525i. Following the introduction of the N20 turbocharged straight-4 engine in 2011, the N53 began to be phased out. The N54 turbocharged straight-6 engine was produced alongside the N53, therefore the N54 took over as the highest performance six-cylinder engine.

Compared with its N52 predecessor which was port-injected, the N53 uses direct injection (consisting of Piëzo-electric injectors directly in the cylinder) with a stratified lean mixture operation. The N53 has variable valve timing on both camshafts(called double vanos by BMW) and a magnesium alloy block. Unlike the N52, the N53 does not contain variable valve lift (called valvetronic by BMW), due to space limitations in the cylinder head.