BMW X5 Owners & Service Manuals

BMW X5: Air Intake Ducting

With regard to the N54 engine, the air intake ducting plays a significant role due to the requirements of a turbocharged engine.

In principle, the energy of the escaping exhaust gases is utilized to "pre-compress" the inducted fresh air and thus introduce a greater air mass into the engine. This is only possible if the air intake ducting is "leak-free" and installed properly.

Engine Service Information
Fig. 35: Identifying Air Intake Ducting Components

It is important to note, when carrying out work on the air-intake ducting, it is important to ensure that the components are installed in the correct position and that all pipes are connected with tight seals.

A leaking system may result in erroneous boost pressure. This would be detected by the engine management system and will ultimately result in "limp-home" operation. There would also be a noticeable reduction in engine power.

For some of the duct work, there are special tools to ensure proper connections.

Air Intake Ducting Function

Engine Service Information

Fig. 36: Identifying Air Intake Ducting Function Diagram

The fresh air is drawn in via the air cleaner (10) and the charge-air suction lines (6 + 18) by the compressors of turbochargers (23 + 24) and compressed.

Because the turbochargers can get very hot during operation, they are connected with the engine's coolant and engine-oil circuits. The charge air is greatly heated when it is compressed in the turbocharger, making it necessary for the air to be cooled again in an intercooler (16).

The compressed and cooled charge air is routed from the intercooler via the throttle valve (12) into the intake manifold.

The system is equipped with several sensors and actuators in order to ensure that the load of fresh air is optimally adapted to the engine's respective operating conditions. How these complex interrelationships are controlled is discussed in the following sections.

Engine Service Information
Fig. 37: Identifying Air Intake Ducting


 Exhaust Gas Turbocharging

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 Boost-Pressure Control

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 Load Control

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