The BMW N54 engine is a 3.0-liter, twin-turbocharged inline six-cylinder engine that was first introduced in the 2006 E90 335i. The BMW N55 engine is a 3.0-liter, twin-turbocharged inline six-cylinder engine that was first introduced in the 2011 F10 535i. The BMW N54 engine produces 300 horsepower and 300 lb-ft of torque. The BMW N55 engine produces 320 horsepower and 332 lb-ft of torque. The BMW N54 engine has a single twin-scroll turbocharger. The BMW N55 engine has two twin-scroll turbochargers.
The BMW N54 engine is the older engine of the two and was used in models such as the 335i, while the BMW N55 engine is the newer engine and is used in models such as the 535i. The BMW N54 engine is considered to be the better engine of the two because it has more power and torque.