BMW N54

The N54 was produced alongside the naturally aspirated BMW N53 engine; both engines have direct injection, double-VANOS (variable valve timing), an open-deck engine block[4][5] and an electric water pump.[6][7][8] Since the N54 is based on the older BMW M54 engine, it has an aluminium engine block (instead of the magnesium alloy used by the N53), a displacement of 2,979 cc (181.8 cu in) and does not have valvetronic (variable valve lift).[9]

Turbocharging is a key difference between the N54 and BMW's previous straight-six engines. The N54 has two small low-pressure turbochargers to minimise turbo lag. BMW's marketed the twin-turbo as "TwinPower Turbo",[10] although the term has since been used for engines which have a single twin-scroll turbocharger.[11] [12] The boost pressure is 8 psi (0.55 bar) and an air-to-air intercooler is used. Compared with the naturally aspirated BMW N52 that it replaced as BMW's highest performance six-cylinder engine, the N54 produces an additional 34 kW (45 bhp) and 108 N⋅m (80 lb⋅ft).[13]

The N54's direct injection system (called "High Precision Injection" by BMW[14]) uses piezo injectors. Its N55 successor uses solenoid-type injectors, because the piezo injectors are more expensive and not reaching their full potential to obtain the "lean burn" benefit.[15]

All versions have a bore of 84.0 mm (3.31 in), a stroke of 89.6 mm (3.53 in), a compression ratio of 10.2:1 and the redline is 7000 rpm.

Car & Driver noted the N54 had minimal turbo lag and "in feel and sound the twin-turbo could pass for naturally aspirated".[28] The N54-engined F01 740i was also praised for its linear power delivery.[29]

Comparing the N54-engined E60 535i with the 550i (using a 4.8–litre naturally aspirated V8), one reviewer noted that the V8 model had more torque but was "only marginally quicker than the 535i" and that the additional weight of the V8 engine was noticeable on twisty mountain roads.[30]

In the United States, some N54 engines experienced failures of the High Pressure Fuel Pump (HPFP), resulting a class action lawsuit, a voluntary recall and an extended warranty for the HPFP.

Failure of the HPFP can cause the engine to suddenly stop functioning, which has caused several near-misses on highways.[31] BMW was aware of HPFP problems, describing them in internal Technical Service Bulletins as "driveability problems".[31]

In April 2009, a class action suit was filed against BMW in connection with HPFP failures.[32][33] BMW settled the suit in June 2010. On 26 October 2010, following an ABC News story about HPFP failures,[34] BMW announced a recall of vehicles with the pump in question from manufacturing years 2007–2010.[35][36] The recall was applied to 130,000 cars, resulting in the replacement of the HPFP in approximately 40,000 of these cars.[37]

In the United States, the warranty period for the HPFP was increased to 10 years and 120,000 mi (190,000 km).[38]

On some cars, the HPFP was replaced multiple times without resolving the issue, potentially leading to the car being refunded under the Lemon Laws in some states.[39]

The High Pressure Fuel Pump issue caused BMW North America to extend the warranty for this pump to 10 years or 120,000 mi (190,000 km).

The warranty period for the fuel injectors was also increased, to 10 years or 120,000 mi (190,000 km).[40][41] An updated design for the fuel injectors was also introduced.[42][43]

Due to problems with rattling wastegates caused by premature bushing wear,[44][45] BMW extended the warranty period for wastegate-related issues to 8 years or 82,000 mi (132,000 km).[46]

These warranty extensions only apply to the United States.

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