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 fuel injection rate 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 unit, the calibration value of each installed injector is stored in the DDE control unit. The calibration values are allocated to the individual cylinders according to the installation of the injectors.
The fuel injection rates calculated by the DDE control unit during engine operation is corrected slightly by these calibration values, thus improving above all the exhaust emissions. If incorrect values are stored, overheating e.g. of the turbocharger can also occur.
The service function can be used to change the calibration values of the fitted injectors in the control unit or store new values.
For the calibration values, the following figures and numbers are used in the MINI (R56):
This calibration value is stamped on the top of each injector (see graphic).
Behind the two-part, 8-digit calibration value (1), an additional single-digit code (2) and a 6-digit number (3) is printed. However, (2) and (3) are not relevant for the adjustment.
Graphic 1: Example of calibration value R56 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 unit.
Note: For cylinders for which no new adjustment value is entered, the old calibration value is retained in the DDE control unit.
Important: If the DDE control unit has been replaced, the injector quantity adjustment also has to be carried out so that the calibration values of the fitted injectors are stored in the new control unit!