The N54 is a twin-turbocharged straight-6 automobile engine from BMW. It 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. It is BMW's first production turbocharged gasoline engine in 26 years since the 745i in 1980. The new engine debuted at the 2006 Geneva Motor Show and won the International Engine of the Year award in 2007 and 2008.
According to BMW, the N54B30 produces 306 hp (228 kW) and 295 ft·lbf/400 N·m. Third party testing has revealed the engine is significantly underrated, producing 332 hp (248 kW) and 311 ft·lbf/422 N·m in one test. 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.
The ample torque of the engine combined with the lack of turbo lag provides the same feel as a small V8. The advantage of the N54B30 engine is that compared to similar power output 225 kW (302 hp) 290 lb·ft (390 N·m) V8 4.0L N62B40 it weighs 70 kg less than the V8, which is massive at 265 kg . Additionally, the N54 has higher low-end torque than the N62. It is likely for these reasons BMW chose to develop bi-turbo inline straight-6 engines for the 3-series instead of using heavier V8 engines.
Only the new BMW M3 will have a V8 engine in the 3-Series lineup, weighing in at 202 kg (445 lb) and generating 414 hp (309 kW) and 295 lb·ft (400 N·m), however this V8 is derived from the V10 engine that powers the BMW M5. Nonetheless the tuned version of the N54, which is found in the 2011 335is and 2009 Z4 sDrive35is, has higher low-end torque than the M3's V8 engine, 332 pound-feet at 1500 rpm for the 35is versus 295 pound-feet at 3900 rpm for the M3, and the V8's higher maximum horsepower of 414 hp (309 kW) is only available at 8300 rpm.