Charging, function - GF09.00-P-2000OM

ENGINE 651.913 in MODEL 204.0/2 

ENGINE 651.925 in MODEL 212.0/2 

Function requirements for charging - general 

• Circuit 87M ON (engine timing ON) 
• Engine running 

Forced induction, general 

The cylinder charging efficiency is improved as a result of forced induction. As a result, the engine torque and power output are boosted. During forced induction, the flow energy of the exhaust gases is used to drive the turbocharger.

The turbocharger suctions in fresh air through the air filter on the compactor inlet and feeds it through the compactor outlet into the charge air pipe upstream of the charge air cooler.

The high speed of the compactor turbine wheel and the resultant high volume flow compactes the air in the charge air pipe. compaction heats the charge air, which now flows through the charge air pipe to the charge air cooler.

This cools off the charge air and feeds it through the charge air pipe to the charge air manifold.

Turbocharging is regulated by the boost pressure control. The boost pressure is regulated by the CDI control unit (N3/9) depending on the following values and associated components:

• Boost pressure sensor (B5/1)
• Coolant temperature sensor (B11/4)
• Charge air temperature sensor (B17/8)
• Pressure sensor downstream of air filter (B28/5)
• Temperature sensor upstream of turbocharger (B19/11)
• Crankshaft position sensor (L5) (except code (B03) ECO start-stop function), for the engine rpm
• Crankshaft Hall sensor (B70) (with code (B03) ECO start/stop function), for engine speed
• The injection quantity which is determined via the injection time of fuel injectors (Y76) and the fuel pressure in the rail. The fuel pressure in the rail is detected by the rail pressure sensor (B4/6).
• Exhaust back pressure sensor (B60), for the exhaust back pressure in the exhaust system
• Atmospheric pressure sensor, for measuring the atmospheric pressure

Function sequence for charging 

After evaluating the input signals, the CDI control unit actuates, based on the charge pressure characteristics map, the boost pressure regulator (Y77/1) by means of a pulse width modulated signal (PWM signal). The position of the guide vanes in the turbocharger are altered via the control linkage of the boost pressure regulator.

The adjustable guide vanes modify the flow cross-section through which the exhaust gas flows to the turbine. The guide vanes thus match the gas pressure present at the turbine to the required boost pressure. The turbocharger speed is used to determine the quantity of compacted air and thus the boost pressure.

The boost pressure is constantly being monitored by the boost pressure sensor and passed on to the CDI control unit.

To protect the turbocharger from thermal and mechanical overload, the CDI control unit monitors the exhaust temperature via the temperature sensor upstream of the turbocharger and the exhaust back pressure through the exhaust back pressure sensor.

The boost pressure is reduced if there is any risk of thermal or mechanical overload.