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Principle of operation Function Oporaelon is basad on ilia fact that the curamic nio particular sensitivity of tho lambda sonsor material is oxygen-con conductive after reach- in the range around A — 1 permits the sensor ing temperatures of approximately 300*C. If the output signal to be fed as an actual value into t oxygen proportions at the two ends of the the control unit of the Jetronic (EFI). Any mix- probe differ, a voltage is generated between ture deviation from the preset value is sensed the two interfaces due to the special properties by the lambda sensor from the residual oxygen of the material used. This voltage is an indica- content of the exhaust gas, and transmitted to tion of the difference in the proportions of oxy- the control unit in the form of an electric signal. ; gen at the two ends of the probe. The control unit determines a change in the in the exhaust gas of internal-combustion duration of Injection, thereby correcting the anginas there are still residual proportions of air-fuei mixture virtually without tag. ' oxygen present, even when combustion takes The A closed loop and EFI systems guaran- place with excess fuel (at ). = 0.95 e. g. 0.2 .. teethe mixture-composition accuracy required 0.3 vol. ;o). The residual oxygen content is for effective operation of exhaust-gas catalysts largely dependent on the composition of the in exhaust-gas decontamination. air-fuei mixture supplied to tho engine for com- bustion. This dependency permits use of the Literature source oxygen content of the exhaust gas to measure VDT- the air-fuel ratio A (See graph below). Bosch Technical instruction Manual VDT- uF3P 751/1 "D- and L-Jetronic". Exhaust-gas testing m!! As the volume of traffic increases in cities, so 1000 SQQ•C too does air pollution. This phenomenon has gWC'-• become an acute hazard to the Inhabitants of -�` '-.• Los Angeles on account of its unfavorable 00 9 •C location as regards climate. For this reason in 1965 the State of California began to limit the emissions of toxic substances from pas- CM songer cars. Today all industrialized countries 600 have legally prescribed exhaust-gas tests. } which vary with regard to the driving cycle, ex- 0 haust-gas collecting and anaiys.s system and m X00 maximum permissible limits. The principle is common to them all. a prescribed driving cycle (regarded as repre- 200 sentative of driveability in particular zones) is simulated on a chassis dynamometer and the quantities of toxic substances emitted are L-Wa��l 0 1determined. The dynamometer can be so ad- 0,7 0.8 0,9 1,0 1,1 1,2 1,3 lusted that the braking power corresponds to Excess-air factor A the resistances encountered in actual road operating conditions and an inertial mass Characteristics of lambda sensor simulates the vehicle weight.