Abstract: The major part of the hazardous material quantities emitted by motor vehicles having an exhaust gas catalytic converter accrues in the start-up phases in which the catalytic converter is not yet at the operating temperature. The catalytic converter first begins to operate after it is heated up to the light-off temperature. The heat-up times must be kept as short as possible. With aging of the catalytic converter, the light-off temperature gradually increases, and thus, the heat-up time as well as the emitted hazardous material quantity also increases. In order to monitor the catalytic converter and thus the major part of the hazardous material emission, the light-off temperature must be repeatedly measured. Since this temperature cannot be read out clearly from the temperature-time curve of the catalytic converter after the start-up of the motor, the signal of a sensor for oxygen, carbon dioxide, water vapor, or combustible materials in the exhaust gas is additionally observed.

Abstract: A new method, to determine and control the air-fuel ratio for motor vehicles by employing a known method to determine the air factor lambda from the partial oxygen pressure of an exhaust gas brought to near total chemical equilibrium condition when knowing the mean chemical composition of the fuel is devised by, in addition to the partial oxygen pressure of the exhaust gas being brought to near total chemical equilibrium condition, the partial oxygen pressure of the exhaust gas that has not been exposed to means for adjusting the chemical equilibrium is measured, and where lambda is determined from the two partial oxygen pressures, the difference of the lambda values is obtained, and this difference is used as a measure for the concentration of the sum of residual hydrocarbons in the exhaust gas.