N54 3.0L Turbocharged 2006 to 2008
The N54 is a direct injection turbocharged straight-6 automobile engine from BMW. It debuted at the 2006 Geneva Motor Show and was launched in late 2006 as a high-performance option for the BMW 3-Series, first to be released along with the new 3-series E92 Coupé, to be followed closely by other existing 3-series models, then with other BMW series as well. The N54 has won five straight International Engine of the Year awards, and three straight Ward's 10 Best Engines awards.
N54B30 (225 kW version)
N54B30 (240 kW version)
N54B30TO (250 kW version)
The use of two small turbochargers plus direct fuel injection allows for a broader power band and less turbo lag than previous turbocharged gasoline engines. Despite its relatively small-displacement, the N54B30 provides the midrange torque of a mid-displacement V8 engine more efficiently and at less weight.
The N54B30 does not use the second generation Valvetronic technology found in the naturally aspirated N52 and the newer (single) twin-scroll turbocharged straight-6 N55. The engine block of the N54 is derived from the older generation BMW M54B30 engine - all aluminum with cast iron cylinder liners. This is because the newer N52 aluminum-magnesium engine block was not deemed as suitable for turbo-charging with the above-mentioned engineering goals. The N54's block size is identical to the older M54B30 at 2979 cc/181 in³ instead of the 2996 cc/182 in³ of the new N52B30 3.0L engine, while the N54 is physically heavier (195 kg (430 lb)) than the very light (161 kg (355 lb)) N52 engine. There are some differences between the M54 and N54; the M54 is a single-piece block, with the water pump housing cast into the block, and is a closed-deck design, compared to the N54's two-piece block with a separate bedplate, electric water pump, and open deck. 
The engine uses two small low-pressure turbochargers to remove turbo lag at low elevations. For this reason, the turbo pressure is only 8.8 psi as the engineering goal was to offer the same driving feel as with naturally aspirated engines. BMW's brand for turbocharging is "TwinPower Turbo".
The engine's gasoline direct injection system uses high-priced piezo injectors, also used in the naturally-aspirated N53 (mostly European markets only). However it was found that the piezo injectors were very expensive and not reaching their full potential when used in North America, in contrast to Europe which they could perform lean burn. The succeeding N55's direct injection uses cheaper Bosch solenoid-type injectors. BMW's trademark for direct injection, regardless of type, is known as "High Precision Injection".
According to BMW, the N54B30 produces 306 hp (228 kW) and 295 lb·ft/400 N·m. Third party testing has revealed the engine is significantly underrated, producing 332 hp (248 kW) and 311 lb·ft/422 N·m in one test
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