Thermal management of N-series engines

In after-sales material, BMW AG mentions, that thermal management of N series is directed by DME.

There are several work modes:

  • mapped: with lowered temperature – around 80 oC;
  • high power: temperature around 95 oC;
  • normal: temperature around 105 oC;
  • eco mode: temperature around 112 oC.

All these modes are maintained, using following components:

a) water pump with manageable productivity (directed via CAN interface);

b) thermostat;

c) heating of thermostat (electrical heater, managed from DME with PWM).


How is the temperature of engine managed?

The mechanical part of thermostat is identical to “regular” thermostat, only difference – the mechanical element can be heated additionally (using electrical heating, managed by DME).

  • High power mode (around 95 oC) is used in conditions of high load to reach maximum engine performance. In this case the water pump and the thermostat are used as in “regular” engines, the temperature of the engine is maintained, changing the productivity of water-pump. Extra benefit – also with low RPM and in idle run (right after high load), electrical water-pump maintains efficient flow of coolant/cooling of the engine.
  • Normal/Eco mode – to rise the temperature, the productivity of water-pump is decreased. Minimal productivity is limited with 15%. Eco mode turns on in case of low load/idle run. The thermostat has opened, and the temperature is maintained, changing the flow of coolant (productivity of water-pump). Conditions, when these modes are activated – oil temperature is not supposed to be significantly lower than the temperature of coolant.

At the same time, the maximum temperature of oil is also controlled – it is limited (typically: 110 oC), decreasing the temperature of coolant as much as needed.

  • Mapped (around 80 oC)  mode uses additional heating of thermostat. In this case – the temperature inside the thermostat reaches it’s (thermostat’s) opening level, even if the coolant is 10 – 15 oC cooler. Productivity of the water-pump is increased (till 75 – 80%) for maximum efficient cooling of the engine.

Mapped mode is used for following modes:

a) in case of essential error messages of engine, for example, if insufficient performance of CO catalytic converter is detected;

b) can be used during warming up of the engine, while the temperature of coolant is significantly different from temperature of oil.


Given that the temperature of coolant is limited according to temperature of oil, readings of oil temperature sensor are critically important!


General information regarding thermal conditions can be found here: ../F5/F2/F6

Information regarding actual heating and manual  control of thermostat can be found here: ../F6/F1/F4

 Information regarding water-pump can be found: ../F6/F1/F8