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.
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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
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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.
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Fig. 37: Identifying Air Intake Ducting
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Exhaust Gas Turbocharging
The turbocharger is driven by the engine's exhaust gases, i.e. exhaust gases
under pressure are routed by the turbocharger turbine and in this way delivers
the motive force to the compressor, which
Boost-Pressure Control
The boost pressure of the turbochargers is directly dependent on the flow of
exhaust gas which reaches the
turbocharger turbines. Both the velocity and the mass of the exhaust-gas flow
are directly
Load Control
Load control of the N54 engine is effected by means of the throttle valve and
the waste gate valves.
The throttle valve is the primary component in this process. The wastegate
valves are actuated t
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Ignition System Diagnosis
The ignition system on modern BMW engines consist of one ignition coil per
cylinder. This arrangement is
known as RZV, or Direct Stationary Ignition. The ignition coil receives fused
power usually from the DME
main relay or IVM (N62).
The ignition coil primary circuit is controlled (triggered) by
