BMW 3 Series Turbo

N47, N57, M47, N54, N55, B47, B48: which engine code needs which new turbo on the Série 3?

On the BMW Série 3, the engine code stamped on the block is the essential starting point. A single commercial designation — 320d, 330d or 335i — covers several engine families depending on the generation (E46, E90/E91/E92/E93, F30/F31/F34) and year of manufacture. Mixing up a M47 D20 and a N47D20A on a 320d means ordering an incompatible turbo: the manufacturer references differ, and the physical fitment does not match.

Diesel: from the M47 family to the N47, N57 and B47 blocks

The 316d, 318d, 320d and variants (320td, 320Cd, 318td) span several generations of 2.0 diesel blocks. E46 versions carry the codes M47 D20 (204D1) or M47 D20 (204D4), while subsequent generations moved to M47N2 / M47TU2 blocks, then N47D20A / N47D20C and finally B47D20A on the facelifted F30/F31. For the 316d and 318d, the codes N47 D20 C and N47N are specific to these lower power outputs and do not share the same turbo references as the 320d of the same generation. The 6-cylinder diesel 325d, 330d, 330xd and 335d use distinct 3.0 blocks: 306D1 / M57 D30 for the early-generation 330d E46/E90, M57306D3 / N57D30A / N57N306D3 for later generations, and N57D30 for the 335D. These 6-cylinder blocks frequently use two turbos in series (twin-turbo with variable geometry on the N57): check how many turbos your engine has before ordering.

Petrol: N20, N54, N55 and the B48 family

The F30-generation 320i and 328i use the 4-cylinder N20B20, with a wastegate, whose turbo references are model-specific. The more recent 320i, 330i and 330e carry the codes B46B20B, B48B20A or B48B20B depending on the power output and plug-in hybrid variant. The 335i is the most complex case: it was produced with both the N54B30A, N54B30B (twin-turbo, two fixed-geometry turbos) and the N55B30A (single variable-geometry turbo). These two architectures are fundamentally different: an N54 takes two turbos, an N55 takes only one. Confusing the two families is the most common mistake on this model. The 335i 306 hp or 340 hp version uses the codes N54B30A, N54B30B or N55B30A depending on the exact year of production. On BMW turbocharged petrol blocks, a clogged lubrication circuit (degraded oil, end-of-life head gaskets) remains the primary cause of turbo bearing failure: always address the root cause before replacing the turbo.