System for internal combustion engine

A control system for a vehicle having a fuel vapor recovery system coupled between a fuel supply system and an intake manifold of an internal combustion engine, comprising:

• purging means coupled to the fuel supply system and the fuel vapor recovery system for periodically purging a vapor mixture of fuel vapor and purged air into the engine air/fuel intake;
• feedback means coupled to an exhaust gas oxygen sensor for providing an air/fuel ratio indication of engine operation;
• first correction means responsive to said air/fuel ratio indication and a measurement of airflow inducted into the engine for providing a base fuel command;
• learning means responsive to a deviation in said air/fuel ratio indication from a desired air/fuel ratio for providing a measurement of fuel vapor content in said purged vapor mixture;
• second correction means for subtracting a value related to said fuel vapor content measurement from said base fuel command to form a modified base fuel command and providing delivery of liquid fuel to the engine in relation to said modified base fuel command;
• and
• purge control means for stopping said purging and said learning means when said fuel vapor content measurement is less than a preselected value.

A control system for a vehicle having a fuel vapor recovery system coupled between a fuel supply system and an intake manifold of an internal combustion engine, comprising;

• induction means for inducting a mixture of ambient air and liquid fuel into the air/fuel intake;
• purging means coupled to the fuel supply system and the fuel vapor recovery system for periodically purging a vapor mixture of fuel vapor and purged air into the engine air/fuel intake;
• adaptive learning means responsive to an air/fuel measurement of engine operation for measuring fuel vapor content in said purged vapor mixture when said adaptive learning mean sis in a first state of operation and for measuring air/fuel offsets over a range of engine operating conditions when said adaptive learning means is in a second state of operation, said adaptive learning means switching from said first stat to said second state when said measurement of fuel vapor content is less than a preselected value;
• feedback means coupled to an exhaust gas oxygen sensor for providing said air/fuel measurement of inducted air and purged fuel vapors and liquid fuel, said feedback means also correcting said liquid fuel inducted into said engine in response to said air/fuel measurement and said fuel vapor content measurement and said air/fuel offset measurement;
• and
• purge control means for stopping said purging when said fuel vapor content measurement is less than said preselected value and for initiating said purging after said purging has been stopped for said preselected time.

A control method for a vehicle having a fuel vapor recovery system coupled between a fuel supply system and an intake manifold of a internal combustion engine, comprising the steps of:

• inducting a mixture of ambient air and liquid fuel into the air/fuel intake;
• periodically purging a vapor mixture of fuel vapor and purged air from said fuel vapor recovery system into the engine air/fuel intake;
• providing an air/fuel measurement of inducted air and purged fuel vapors and liquid fuel;
• measuring fuel vapor content in said purged vapor mixture in response to said air/fuel measurement;
• disabling said step of purging when said fuel vapor measurement is less than a predetermined value;
• measuring air/fuel offsets over a range of engine operating conditions in response to said air/fuel measurement for a predetermined time after said purging is disabled and reenabling said purging step after said predetermined time;
• and
• correcting said liquid fuel inducted into said engine in response to said air/fuel measurement and said fuel vapor content measurement and said air/fuel offset measurement.