Lsf Lambda Sensor - PGO Tigra AF-125BAE Service Manual

11-4 LSF Lambda sensor

Function:
Test the oxygen content in exhaust to make
sure of the mixture of gasoline and air
completely burned and promote the
Air/Fuel Ratio precisely controlled by
ECU.
Theoretical Air/Fuel Ratio: 14.7:1
Principle:
When a ceramic tube's temperature is up to 350℃, the solid ceramic electrolyte is conductive and the oxygen
molecule inside and outside ceramics is catalyzed to oxygen anion, which freely moves inside ceramics, by the
sensor's platinum electrode so that oxygen molecule thereof diffuses via ceramics. Due to this characteristic,
the difference in concentrations of oxygen inside and outer ceramics could be transferred to the potential
difference and further electrical signal outputs. In virtue of the signals' voltages changing at the theoretical
equivalent air/fuel ratio (λ=1), it is necessary for a gasoline engine to keep the excess air coefficient  in the
range between 0.85 and 1.10, shown as follows.
Excess air coefficient (): Ratio of a mixed gas's actual air/fuel ratio to a theoretic equivalent air/fuel ratio.
=1: Mixed gas's actual air/fuel ratio = theoretic equivalent air/fuel ratio;
1: Mixed gas's actual air/fuel ratio > theoretic equivalent air/fuel ratio; thin mixed gas; voltage output
low (about 100mV)
1: Mixed gas's actual air/fuel ratio < theoretic equivalent air/fuel ratio; thick mixed gas; voltage output
high (about 800mV~1000mV)
Fig. 11-4.2, Characteristic curve of a Lambda sensor at 600C
Fuel Injection System 7
Fig. 11-4.1, Lambda sensor
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