Engine cooling

The opening and closing of the mapped thermostat is controlled by a characteristic map. This regulating operation can be split into 3 operating ranges:

• Mapped thermostat closed:

  The coolant only flows through the engine and the coolant circuit is closed.

• Mapped thermostat open:

  The entire coolant volume flows through the radiator. This results in maximum use of the available cooling output.

• Control range of the mapped thermostat:

  A proportion of the coolant flows through the radiator. The mapped thermostat maintains a constant coolant temperature within the control range at the engine inlet.

  In this operating range, the coolant temperature can now be selectively controlled with the assistance of the mapped thermostat. This means that a high coolant temperature can be set in the part-load range of the engine. High operating temperatures in the part-load range result in improved combustion. This in turn leads to reduced consumption and exhaust emissions.

  During full load operation, certain disadvantages are associated with higher operating temperatures (retarding of ignition due to knock).

  A lower coolant temperature is therefore specifically set during full load operation with the assistance of the mapped thermostat.