Description

Description

Mixture Primary Control
The air mass taken in by the engine and the engine speed are measured. These signals are used to calculate an injection signal. This mixture primary control follows fast load and speed changes.

Lambda-Control
The ECM compares the oxygen sensor signal of the sensor upstream of the catalyst with a reference value and calculates a correction factor for the primary control.

Adaptive Primary Control
Drifts and faults in sensors and actuators of the fuel delivery system as well as un-metered air leakage into the intake system influence the primary control. This causes deviations in the air fuel ratio. The adaptive primary control determines the controller correction in two different ranges.

Ranges of Learning Correction Coefficients tra and fra







Range 1 Determination of additive correction per time unit
Range 2 Determination of multiplicative correction

Lambda deviations in range 1 are compensated by an additive correction value multiplied by an engine speed term. By this means an additive correction per time unit is derived.

Lambda deviations in range 2 are compensated by a multiplicative factor.
Each value is determined only within its corresponding range. But each adaptive value corrects the primary control within the whole load and speed range of the engine. After the next start, the stored adaptive values are included in the calculation of the primary control; just before the closed loop fuelling control is activated.

Abbreviations for the fuel delivery system
NU1 Upper engine speed threshold, range 1
QU1 Upper air flow threshold, range 1

tra Additive learning correction coefficient per time unit (range 1)
TRADN Lower diagnosis threshold of tra
TRADX Upper diagnosis threshold of tra

QL2 Lower air flow threshold, range 2
QU2 Upper air flow threshold, range 2
RLU2 Upper engine load threshold, range 2
RLL2 Lower engine load threshold, range2

fra Multiplicative learning correction coefficient (range 2)
FRADN Lower diagnosis threshold of fra
FRADX Upper diagnosis threshold of fra

Diagnosis of fuel delivery system
Faults in the fuel delivery system can occur which cannot be compensated for by the adaptive control.

In this case the adaptive values leave a predetermined range.
If the adaptive value is outside this predetermined range, and if the condition is again present on a subsequent drive cycle, the MIL is illuminated and the appropriate DTC's are stored.