The tolerances given to the injectors on manufacture mean that the actual injected volume of fuel deviates slightly from the theoretically calculated volume of fuel. These injection volume tolerances are determined for each injector across the entire operating range following manufacture by measurements at the suppliers. From these measurements, a calibration value is generated for each injector.
During vehicle assembly, after installation of the DDE control module, the calibration value of each installed injector is stored in the DDE control module. The calibration values are allocated to the individual cylinders according to the installation of the injectors.
The injection volume calculated by the DDE control module during engine operation is corrected slightly by these calibration values thus improving the exhaust emissions.
The service function can be used to change the calibration values of the fitted injectors in the control module or store new values.
The structure of the alphanumeric calibration value depends on the exhaust emission stage of the engine:
This calibration value is stamped on the top of each injector, see illustrations below.
Behind the calibration value, an injector ID has also been stamped (2), but this is not relevant to the calibration. The injector ID is slightly offset from the calibration value and it has a slightly larger font size.
Fig. 1: Example of calibration value EURO 3, first version
Fig. 2: Example of calibration value EURO 3, second version
Fig. 3: Example of calibration value EURO 4
Important: If injectors have to be replaced, it must be ensured that the stamped calibration value of each injector is assigned to the right cylinder in the DDE control module.
Note: For cylinders for which no new calibration value is entered, the old calibration value is retained in the DDE control module.
Caution: If the DDE control module has been replaced, the injector volume calibration also has to be carried out so that the calibration values of the fitted injectors are stored in the new control module!