BMW X5: 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 to bring about a fine tuning of the boost pressure. At full load the throttle valve is completely open and load control is undertaken by the wastegate valves.
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Fig. 43: Identifying Load Control Operations Diagram
Controlled Variables
The following variables, among others, influence control of the N54 engine's boost pressure:
- Intake-air temperature
- Engine speed
- Throttle-valve position
- Ambient pressure
- Intake-manifold pressure
- Pressure before the throttle valve (reference variable)
The electropneumatic pressure transducers are activated by the engine control unit on the basis of these variables. The result of this activation can be checked from the boost pressure achieved, which is measured before the throttle valve.
There follows a comparison of the boost pressure achieved with the set point data from the program map, which can if necessary give rise to an activation correction. The system therefore controls and monitors itself during operation.
Limp-home Mode
In the event during operation of malfunctions, implausible values or failure of any of the sensors involved in turbocharger control, activation of the wastegate valves is shut down and the valve flaps are thus fully opened.
Turbocharging ceases at this point.
The list below sets out those components or functional groups of the N54 engine in which a failure, a malfunction or implausible values result in boost-pressure control being deactivated.
The driver is alerted to a fault of this type via an EML indication.
- High-pressure fuel system
- Inlet VANOS
- Exhaust VANOS
- Crankshaft sensor
- Camshaft sensor
- Boost-pressure sensor
- Knock sensors
- Intake-air temperature sensor
One principle of vehicle repair is particularly important in this respect: It is important to focus on the causes rather than the effects.
With regard to diagnosis of the turbocharging system, always check the basics first. Look at such items as the vacuum hoses, the solenoids and the vacuum reservoir.
Don't overlook the fundamentals. Check compression, fuel system pressure (low and high), secondary ignition components etc.
The turbochargers are usually the last item to fail, but often one of the first items to be replaced.
READ NEXT:
Turbocharger Diagnosis
There are three "Golden Rules" to adhere to when diagnosing concerns on the
N54 engine:
1. When diagnosing cases of smoke from the exhaust, it is important to avoid
unnecessary replacement of
the tu
N52KP And N51 Fuel System
The N52KP and N51 engine continue to use the conventional "manifold
injection" system carried over from the N52. The fuel supply components are also
carried over with regard to the EKP module, fuel
SEE MORE:
Welding And Soldering Steel Parts
IMPORTANT: Comply with the following topics from "Body, General":
Safety regulations.
Handling electrical/electronic equipment, airbags and restraint
systems.
A. Welding steel parts:
General information
The following procedures are used for repairs:
MAG welding (M etal A ctive G as welding)
Refrigeration Oil
OIL USED IN FREON-CHARGED SYSTEMS
A mineral-based oil is used. The oil level in the compressor must be checked
before filling an air conditioner
with refrigerant. It can be checked only if the system is without refrigerant.
Always check the oil level each time a new system is filled with Freon R12
