BMW 3: Operating strategy

The following graphic shows the positions of the rotary valve as the coolant temperature increases:

Switching diagram heat management module

0% - Rotary valve closed
100% - Rotary valve open

1. Cold start
2. Warm-up phase
3. Operating temperature
4. Transition from normal operation to maximum cooling requirement
5. Maximum cooling requirement

X - Rotational angle in angular degrees

1. Heater circuit
2. Main coolant circuit
3. Minor coolant circuit

The openings on the rotary valve vary the cross-sections of the different coolant ducts as a function of the rotational angle of the rotary valve. The following graphics schematically represent the various engine operation phases, from cold start to maximum cooling requirement.

Cold-start phase

Point A in the heat management module circuit diagram designates the cold start with an engine that has completely cooled down.

Cold-start phase

In the cold-start phase, the coolant circulates exclusively via a bypass in the coolant pump. The rotary valve in the heat management module closes the coolant lines so that the excess pressure that builds up opens the pressure relief valve in the coolant pump (opening pressure 2.2 bar) and the coolant is recirculated in the coolant pump.

Because the coolant circuits through the exhaust turbocharger and the ventilation line of the cylinder head cannot be closed, a low volumetric flow is returned to the coolant pump here.

Warm-up phase

Area A in the circuit diagram for the heat management module shows the opening angle of the rotary valve in the warm-up phase.

Warm-up phase

In the warm-up phase, the heat management module additionally opens the connection to the heating in addition to opening the bypass line. The coolant flows through the cylinder head, the exhaust turbocharger and the engine oil/coolant heat exchanger. The electrical Split Cooling Valve is closed; no coolant flow through the engine block (Split Cooling).

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