BMW Injector volume calibration / compensation explanation

Injector volume calibration 

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, two calibration values are generated for each injector.

During vehicle assembly, after installation of the DME control module, the calibration values of each installed injector are stored in the DME control module. The calibration values are allocated to the individual cylinders according to the installation of the injectors.

The injection volumes calculated by the DME control module are corrected by these calibration values, thus improving the exhaust emissions.

The service function can be used to change the calibration values of the injectors in the control module or store new values.

The calibration values are printed in two blocks each with three digits on each injector (see graphics below). The inscription can be located either on the plastic bracket or the metallic upper part.

 

 Graphic 1: Example of inscription of the calibration values on the plastic bracket

 

Graphic 2: Example of inscription of the calibration values on the metallic upper part

 

Important:

If injectors are renewed or replaced, it must be ensured that the printed calibration values of each injector are assigned to the right cylinder in the DME (digital engine electronics) control module!
The injectors must be removed if the calibration values cannot be read out while they are fitted.
If the engine has already been operated with the injectors, the seal must be replaced before installation.
Ensure that the repair instructions are followed!

Important:

Conversions within the DME control module mean that the last position of the calibration values can differ slightly after saving the entered values. There is no input or control-module fault!

Important:

If the DME control module has been replaced, the calibration of the injectors must also be carried out so that the calibration values of the fitted injector are stored in the new control module! Otherwise, either rough engine operation is possible or the engine might not start.

Note:

For cylinders where no new calibration value is entered, the existing calibration values are retained in the DME control module.

 

Performing Injection quantity compensation using a BMW certified tool :

• Connect diagnosis system:

- Vehicle identification

- Function selection

- Select "Service functions" 

Select "Engine electronics" 

- Select "Adjustment functions"

- Select "Adjust injectors"

- Injection quantity compensation

For each replaced injector, the adjustment value must be entered according to the installation location (cylinder), this also means the adjustment value must be entered for each cylinder.