BMW Série 3 Turbo

N47, N57, N54, B48… which engine code determines the turbo on the BMW Série 3?

On the Série 3, the engine capacity shown on the spec sheet is not enough to identify the turbo — it is the engine code that decides. A 320d can come with a M47 D20 (204D1 or 204D4) on the E46, a N47 D20 A or N47 D20 C on later generations, or a B47 D20 A on more recent versions — three engine families, three distinct turbos, with outputs ranging from 150 hp to 200 hp depending on the variant. The code can be read on a label attached to the engine block or in the manufacturer's documentation.

Diesel: from the M47 family to the N47 and N57 blocks

The 316d and 318d covered here are built, depending on the generation, around engine codes M47TU2, N47 D20 A or B47 D20 A — each with its own distinct variable-geometry turbo. The 325d, 330d and 330xd use the M57 D30 or N57 D30, 6-cylinder in-line blocks that the 335d inherits in a higher-output version (M57306D3 / N57306D3). On these diesel blocks, oil circuit contamination and lubricant degradation are the primary causes of turbo failure: worn bearings, excessive axial play, and turbine-side seal leaks. Before any replacement, identifying and correcting the root cause is essential — failing to do so risks damaging the new part very quickly.

Petrol: N54, N55, N20 and the B48 family

The 335i illustrates the variety of petrol engine codes across this generation: N54 B30 A, N54 B30 B (twin-turbo) and N55 B30 A (single variable-geometry turbo) are three entirely different architectures, and are not interchangeable. The more recent 320i, 328i and 330i use the B48 B20 A, B48 B20 B or B46 B20 B blocks, whilst intermediate versions (320i, 328i on certain model years) use the N20 B20. On N54 twin-turbo blocks in particular, an air leak upstream or insufficient lubrication at start-up produces the characteristic whistling and loss of boost pressure. The vast majority of turbos available here are new; a reconditioned turbo is offered on certain 335i / 335xi and 320d 200 hp references — the product page specifies the type for each manufacturer reference.