The 2014–2019 BMW M3’s turbocharged inline-six engine is the S55. More fully, the engine is commonly identified as the S55B30, a 3.0-litre BMW M powerplant.
The S55 replaced the naturally aspirated V8 used by the previous-generation E90 M3. It retained BMW M’s high-revving performance character while adding two turbochargers, making the F80 M3 the first turbocharged production M3.
BMW developed the S55 from the N55 production engine, but substantially reworked it for motorsport-style demands. M-specific changes included a closed-deck block, strengthened internals, revised cooling and lubrication systems, and twin-scroll turbocharging. The engine produced 431 hp in the standard F80 M3 and later outputs rose in Competition versions.
Common mix-ups include the N54 and N55, which are related BMW turbocharged six-cylinder engines, and the S54, the naturally aspirated inline-six associated with the earlier E46 M3. The S58 succeeded the S55 in newer M cars.