Mean Volume Adaptation

The mean volume (quantity) adaptation is a learning process in which the air/fuel ratio (lambda value) is corrected by the adjustment of the air mass or exhaust gas recirculation. Unlike the other processes, this process affects all fuel injectors equally rather than the individual fuel injector.

An injection volume averaged across all cylinders is calculated from the lambda value measured by the oxygen sensor and the air mass measured by the hot-film air mass meter. This value is compared with the injection volume specified by the digital diesel electronics.

If a discrepancy is detected, the air mass is adjusted to match the actual injection volume by an adjustment of the exhaust gas recirculating valve. The correct lambda value is set in turn.

The mean volume adaptation is not an "instantaneous" regulation but an adaptive learning process. The injection volume error is taught into an adaptive characteristic map that is permanently stored in the EEPROM of the control unit.

Replacing the following components will require a reset (clearance) of this mean volume adaptation characteristic map:

• Hot-film air mass meter
• Fuel injector(s)
• Rail pressure sensor

It is possible to reset the characteristic map with the BMW diagnosis system.