Zero quantity calibration

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In the case of common rail injection , especially with very small injection quantities, tolerances of the injectors and their electrical control have a considerable effect on the injected quantity and thus also on the generation of pollutants . The zero-quantity calibration called (NMK) is also zero quantity adaptation (NMA) is a function of the diesel control unit , which measures in injection pauses (z. B. in thrust) by brief actuation of the injectors with increasing duration from when the micro-injection on the torque of the engine affects.

The two main influencing variables on an exact injection are the injected amount of fuel (see: injector volume adjustment ) and the injection duration. For an exact control it is essential to determine when the injection is really effective. The aim of the zero quantity calibration is therefore to determine the opening time delay of the individual injectors , which changes over time due to wear. The values ​​determined are then added to those stored in the map. The zero quantity calibration usually takes place cyclically in order to adapt the injection to the changing behavior of the injectors.

literature

  • Robert Bosch GmbH: Diesel engine management. 4th edition, Vieweg, 2004, ISBN 3-528-23873-9
  • Konrad Reif: Automobile Electronics: An Introduction for Engineers. 5th edition, Springer Vieweg, 2014, ISBN 978-3-658-05047-4