BMW 3 Series Turbo

Turbo BMW Série 3: from the M47 block of the first diesel generations to the N47, N57 and B-series blocks — which reference for which engine?

The answer comes down to two criteria: the engine code stamped on the block and the exact power output of your variant, as several Série 3 variants share the same engine capacity yet use different turbos. The collection covers all turbocharged diesel and petrol generations, from the M47 D20 (204D1, 204D4) fitted to the E46 through to the B47 and B48 blocks found in the most recent versions, taking in the N47, N57, N54 and N55 families along the way.

Diesel: why the engine code takes precedence over the stated power output

The 320d is a telling example: outputs of 150, 163, 177, 184 or 200 hp can correspond to different variable-geometry turbos depending on whether the block is a M47 D20, N47 D20 A, N47 D20 C or N47D20O1. A 163 hp unit may therefore take a turbo from the M47N2/M47TU2 or the N47 D20 — these are not the same part. On the 330d and 325d, the codes M57 D30, M57306D3, N57D30A and N57N306D3 denote successive generations of the six-cylinder diesel, each with its own turbo mapping. The 335D uses the N57D30, a sequential twin-turbo block whose variable geometry on the low-pressure stage is a specific feature to identify before ordering. On the 316d and 318d, the codes N47 D20 A, N47 D20 C, N47N and B47D20A follow one another according to the vehicle's generation: confusing an N47 with a B47 will result in ordering an incompatible part.

Petrol: N54, N55, N20 and B-series — very different turbocharging architectures

The 335i is the most widely represented petrol engine in the collection. The codes N54B30A and N54B30B correspond to a twin-turbo fixed-geometry architecture with a wastegate, whereas the N55B30A moves to a single variable-geometry turbo: the parts are strictly different and cannot be substituted between one architecture and the other. The 328i and certain 320i models use the N20B20, a four-cylinder with a single turbo. The more recent 320i, 330i and 330e models carry the codes B46B20B, B48B20A or B48B20B, the B-series family with direct injection and a turbo integrated into the exhaust manifold. On these petrol engines as on the diesels, the most common causes of turbo failure are degraded lubrication (old oil or a blocked circuit), fouling from blow-by gases, or a foreign body on the intake side. Addressing the root cause before replacement is essential to the longevity of the new or reconditioned part.

New or reconditioned turbo depending on the engine

The vast majority of engines in this collection are supplied with a new turbo, sold with no old unit to return. The reconditioned turbo is available on 2 specific references: the 335i / 335xi (N54 B30, N55 B30) and the 320d 163-184-200 hp (N47D20A, N47D20C, N47D20O1). For these 2 engines, both options are available within the collection. The BMW manufacturer reference remains the most reliable identification guide; the equivalent references listed on each product page allow cross-checking against the number on the original turbo.