Charging Pressure Regulation

Charging pressure in the inlet manifold is principally controlled by engine speed and load. Charging pressure is limited under high loads by a charge pressure regulator. The charge pressure regulator is located on the exhaust side of the engine and controls the exhaust gas flow through a bypass duct at the side of the turbine.
The charging pressure regulator valve (wastegate) is closed when the load on the engine is normal or less. As the load increases and the charging pressure approaches the maximum preset limit, the wastegate opens allowing some of the exhaust gases to pass through the bypass duct thereby decreasing the load on the turbine.
The charging pressure regulator is a flap valve which closes or opens the bypass duct at the side of the turbine impeller. The flap valve is actuated by a rod from a diaphragm capsule located at the compressor housing. A spring in the diaphragm capsule closes the flap. The diaphragm is activated by pressure from the compressor. When pressure in the compressor is greater than that of the spring, the flap is opened releasing gas pressure from the side of the turbine thus reducing the load to which it is subjected. This in turn reduces compressor pressure.
In the event of a stuck charge pressure regulator, an overpressure relief system is provided to prevent overloading the engine. The overpressure switch is located under the dashboard on the same mounting bracket as the flasher relay. The fuel pump relay also has an extra function that cuts off the fuel pump if engine speed exceeds 6000 RPM.