Engine cooling
The cooling system consists of coolant cooling and a circuit for engine oil cooling. The branch that leads to the engine oil cooler also cools the exhaust turbocharger.
Overview:
| Index | Explanation |
|---|---|
| 1 | Radiator (coolant and air) |
| 2 | Electric fan |
| 3 | Exhaust turbocharger |
| 4 | Turbocharger coolant pump |
| 5 | Engine oil cooler (engine oil and coolant) |
| 6 | Coolant pump |
| 7 | Heat exchanger for heating system |
| 8 | Gearbox oil cooler (gearbox oil and coolant) |
| 9 | Coolant temperature sensor |
| 10 | Characteristic map thermostat |
| 11 | Expansion tank |
The map thermostat opens and closes, regulated by a characteristic map. This regulating operation can be split 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 results in maximum use of the available cooling power. 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 partial load range of the engine. At higher operating temperatures in the part-load range, friction is reduced. This in turn leads to reduced consumption and pollutant emissions. During full load operation, certain disadvantages are associated with higher operating temperatures (ignition advance reduction due to knock). For this reason, during full load operation, the map thermostat is used to specifically set a coolant temperature of 85 °C.