Because the mechanical tolerances of the fuel injector solenoid valves change in the course of their service life, the IDM has to be adapted at regular intervals to take account of the changed fuel injector tolerances.
Adaptation is done individually for each cylinder over a period of 900 seconds per cylinder. The individual adaptation processes are performed in the same order as the firing sequence. The process is started with cylinder 1.
For adaptation to be carried out, the following conditions must be met:
โข Engine temperature at least 70 ยฐC,
โข Engine speed between 1800 and 3500 rpm,
โข Vehicle speed between 50 โฆ 70 km/h.
If this range is left during an adaptation process (i.e. the conditions are no longer satisfied), the adaptation process is stopped and then continued again when the values are once more within the range.
The pilot injection is deactivated when the adaptation is taking place.
The IDM sends the fuel injector solenoid valve an injection signal with a period of time (e.g. 8 ms) stored in the map.
The IDM can determine from the power consumption of the solenoid valve whether the solenoid valve can carry out the commands of the IDM or whether it is responding more quickly (for example in 7 ms) or more slowly (for example in 10 ms). The power consumption of the solenoid valve therefore acts as a reference to the signal sent by the IDM.
If there is a discrepancy between the signal sent and the response of the solenoid valve, an adaptation process must be carried out in the adaptive map tables.
NOTE: During the adaptation process, the injection signal is so short that the injector needle is not raised to inject any fuel. The result: during this period misfires occur and may be noticed in the aforementioned engine speed and vehicle speed range.
Note: Concerns may result if, in extreme cases, the operating conditions that would allow an adaptation process to take place, have not occurred for a long time.
These concerns may relate to:
โข rough engine running,
โข increased emissions of black smoke,
โข loud combustion noise.
After the adaptation process has been completed for one cylinder, the process then continues with the next cylinder (in accordance with the firing sequence).