1.6.2.4 Operation Sequence

The function works independently for each cylinder bank. The intrusion loops for each bank take place one after another.

As soon as the function is active, all cylinders of one bank are shifted one after another towards a lean air fuel ratio until a calibratable difference in the engine roughness (ΔER_sp ) compared to the non-shifted cylinder is reached. This lean shift is applied without changing the average air fuel ratio of the bank since all other cylinders are shifted rich in parallel. The lean shift of each cylinder starts neutral, i.e. all cylinders are shifted back to the original injection timing after the calibrated difference in the engine roughness is reached.

For each cylinder the needed change in injection timing (Δt_i ) and the corresponding change in AFR (Δl_i ) are stored. After all cylinders of one bank have been shifted, the average change in AFR is calculated and compared to the cylinder individual AFR changes, hence a cylinder individual AFR deviation and the needed correction factors for the injection timing are achieved.

The filtered correction values are stored as cylinder individual adaptation values. If these adaptation values exceed a maximum of fall below a minimum limit, a diagnostic trouble (DTC) code is set.

Additionally, a DTC is set, if the predicted adaptation values exceed or fall below certain limits. The predicted adaptation values are calculated out of the old adaptation values and the non-filtered correction values after an entire diagnostic loop.