N55

N55 is a designation used for several distinct things, most notably a BMW Group engine and, in infrastructure, a road designation in Ireland. The term appears in different contexts, so a single article must distinguish between them.

The BMW N55 engine is a 3.0-liter inline-six turbocharged powerplant introduced in the late 2000s as the successor to the N54. It incorporates direct fuel injection, Valvetronic variable intake, Double-VANOS variable cam timing, and a single twin-scroll turbocharger with intercooling. Power outputs for the N55 vary by model and market, but are typically in the range of roughly 300 to 320 horsepower, with torque around 300 lb-ft (approximately 400 Nm). The engine has been used across a wide array of BMW vehicles, including sedans, coupes, convertibles, and SUVs, often paired with an eight-speed automatic transmission, and in some earlier configurations with manuals. The N55 is generally praised for smooth throttle response and broad low-end torque compared with its predecessor, though it shares some maintenance considerations common to modern turbocharged engines, such as potential issues with high-pressure fuel system components. Production and deployment of the N55 gradually gave way to the newer B58 engine family in many markets.

In addition to the automotive usage, N55 serves as a road designation in the Irish road network, where N prefixes identify national routes; the N55 refers to a specific national road within that system. Beyond these uses, N55 may also appear as a product or model code in other industries, reflecting its role as a generic alphanumeric designation.