Double air-fuel ratio sensor system having improved response characteristics

摘要

In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, a delay operation is performed upon the output of the downstream-side air-fuel ratio sensor, so that the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side air-fuel ratio sensor and the delayed output of the downstream-side air-fuel ratio sensor.