An engine should operate satisfactorily under all operating conditions and ensure the energy it receives is utilised to a maximum. The fuel-air mixture must be optimally prepared for this purpose. Only in this way can effective combustion take place and provide the corresponding engine power output. Added to this, effective combustion also ensures that pollutant emissions are kept within acceptable limits.
Adaptation makes it possible for the engine control unit to learn certain values from components and equipment variants, thus making it possible to compensate for certain component tolerances. A fault is indicated if adaptation exceeds certain limits.
Lambda adaptation serves the purpose of compensating for component tolerances that influence the mixture and ageing effects.
Factors such as secondary air and fuel pressure also have an effect on lambda adaptation and are, in part, also compensated.
For this reason, exact intervention limits in the case of fault cannot be specified.
Lambda adaptation differentiates between idle (additive) and partial load (multiplicative) mixture adaptation:
- Idle adaptation is effective at idle speed and in the range close to idle speed. Its influence decreases as the engine speed increases (an important factor is secondary air for instance). The multiplicative mixture adaptation is measured or calculated or as a percentage.
- Partial load adaptation is effective over the entire characteristic map range (an important factor is the fuel pressure for instance) The additive mixture adaptation is measured or calculated in mg/stroke.
This test module is started automatically if faults regarding the mixture composition are stored in the engine management system. For this, the S54 engine has the two faults 2A2E and 2A2F. Faults in the mixture composition can have very different causes. This means that the intake area, exhaust system, and the fuel system must be checked.
Usually, if faults in the mixture composition are stored, other faults are stored in the engine system. It is recommended to start troubleshooting there.