Engine cooling

The map thermostat opens and closes, regulated by a characteristic map. This regulation can be divided into 3 operating ranges:

• Engine cold, map thermostat closed:

  The coolant only flows in the engine (short circuit). The cooling circuit is closed. The thermostat is not activated.

• Engine hot, map thermostat open:

  The entire volume of coolant flows via the radiator. This means that the maximum available cooling output is exploited.

  The thermostat is not activated.

• Control range of the map thermostat:

Part of the coolant flows through the radiator. The map thermostat opens as of 105 °C and maintains a constant coolant temperature. In this operating range, the map thermostat can now be used to influence the coolant temperature specifically. This enables the setting of a higher coolant temperature in the part-load range of the engine. At higher operating temperatures in the part-load range, friction is reduced. This results in lower consumption and pollutant emissions. During full-load operation, higher operating temperatures involve disadvantages (retarding of the ignition due to knocking). For this reason, during full-load operation, the map thermostat is used to specifically set a coolant temperature of 85 °C.