BMW 3 Owners & Service Manuals

BMW 3: Load point increase

Raising the load of the combustion engine at consistent engine speed is called load point increase.

This results in an increase in performance and the option to operate the combustion engine in the optimal range. The arising resistance, which counteracts the combustion engine, must be compensated so that on the one hand the load of the engine increases, and on the other hand the speed remains constant.

An example of this is the switching on of the air conditioning or the rear window heating in vehicles that are powered by combustion engine alone. The DME assumes the balancing of the additional resistance by feeding more fresh air to the combustion engine. The injected fuel quantity is also increased. The load of the combustion engine increases and is in a more optimal range in terms of efficiency and fuel consumption. However, this control happens so precisely that there is no engine speed increase, but only the occurring resistance is compensated.

In the G20 PHEV the electrical machine generates a counter-torque in alternator mode. As described above, the DME compensates this counter-torque and the combustion engine is operated more optimally. The electrical energy gained is used to charge the high-voltage battery unit. In this way, the combustion engine is also positively influenced during charging of the high-voltage battery unit.

The load point increase happens in addition to the already existing power requirement. This process is unnoticeable to the driver. Factors which are decisive over time and level of the load point increase:

  • State of charge of the high-voltage battery unit
  • Temperature of the combustion engine
  • Load of the combustion engine
  • Driving mode

Load point reduction

In order to reduce fuel consumption, the combustion engine can be relieved by a load point reduction if the high-voltage battery unit is sufficiently charged. The high-voltage battery unit is specifically discharged and the state of charge is reduced, although the vehicle is not being driven by purely electrical means.

"Coasting" function

As is already the case in all current hybrid vehicles, the G20 PHEV also has a "coasting" feature.

"Rolling without energy consumption" (coasting) means that the combustion engine is also shut down at higher speeds up to approximately 100 mph (160 km/h ) if it is not required for the drive. At the same time the separating clutch in the drive train is opened so that the vehicle rolls without engine braking effect. The advantage of increased efficiency through "coasting" is clearly visible: in this operating condition no fuel is consumed.

Hybrid-specific Check Control messages

If faults occur in the G20 PHEV, the driver is informed thereof via Check Control messages.

The following table summarizes the key hybrid-specific Check Control messages:

Hybrid-specific Check Control messages


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