Control system and method for engine

A fuel-air control system for an internal combustion engine having at least two combustion chambers, a fuel-air introducing system for supplying a fuel-air mixture to each of said combustion chambers, an exhaust system for collecting exhaust gases from said cylinders and discharging them to the atmosphere, an air-fuel ratio sensor associated with only one of said combustion chambers for sensing the air-fuel ratio in that combustion chamber, feedback control means for adjusting the air-fuel ratio in each of said combustion chambers by adjusting the fuel-air induction system associated therewith, at least one engine running condition sensor, an open control system for adjusting the air-fuel ratio in each of said cylinders in response to the output of said engine running condition sensor, and means for selectively changing the mode of engine control between feed back and open control,the amount of incremental adjustment in fuel-air ratio is made lesser during the initial time period when switching from open control to feedback control than after the target range has been reached the first time in the feedback control mode.

A fuel-air control method for an internal combustion engine having at least two combustion chambers, a fuel-air introducing system for supplying a fuel-air mixture to each of said combustion chambers, an exhaust system for collecting exhaust gases from said cylinders and discharging them to the atmosphere, an air-fuel ratio sensor associated with only one of said combustion chambers for sensing the air-fuel ratio in that combustion chamber, and feedback control means for adjusting the air-fuel ratio in each of said combustion chambers by adjusting the fuel-air induction system associated therewith, said method comprising the steps of controlling the combustion chamber with which the sensor is associated to provide the target air-fuel ratio and providing a leaner than target air-fuel ratio for the combustion chamber with which the sensor is not associated.

A fuel-air control method for an internal combustion engine having at least two combustion chambers, a fuel-air introducing system for supplying a fuel-air mixture to each of said combustion chambers, an exhaust system for collecting exhaust gases from said cylinders and discharging them to the atmosphere, an air-fuel ratio sensor associated with only one of said combustion chambers for sensing the air-fuel ratio in that combustion chamber, feedback control means for adjusting the air-fuel ratio in each of said combustion chambers by adjusting the fuel-air induction system associated therewith, at least one engine running condition sensor, an open control system for adjusting the air-fuel ratio in each of said cylinders in response to the output of said engine running condition sensor, said method comprising the steps of selectively changing the mode of engine control between feed back and open control and making the amount of incremental adjustment in fuel-air ratio lesser during the initial time period when switching from open control to feedback control than after the target range has been reached the first time in the feedback control mode.