Air/fuel control system with catalytic converter monitoring for a variable displacement engine
First Claim
1. A control method for an engine having a catalytic converter and first and second exhaust gas oxygen sensors respectively positioned upstream and downstream of the converter in the engine exhaust stream, comprising the steps of:
- activating a preselected group of cylinders in a first engine operating mode and activating all engine cylinders in a second engine operating mode;
providing a converter test period when a count in output transitions of the upstream sensor reaches a first preselected value while operating in said first mode and a count in transitions of the upstream sensor reaches a second preselected value while operating in said second mode;
generating an upstream count by counting said output transitions of the upstream sensor during said test period;
generating a downstream count by counting output transitions of the downstream sensor during said test period; and
indicating converter efficiency from a ratio of said downstream count to said upstream count during said test period.
2 Assignments
0 Petitions
Accused Products
Abstract
A control system and method for indicating the efficiency of a catalytic converter coupled to a variable displacement engine. A preselected group of cylinders is activated in a first engine operating and all cylinders are activated during a second engine operating mode. A converter test period is provided when a count in output transitions of the upstream sensor reaches a first preselected value while operating in the first mode and count in transitions of the upstream sensor reaches a second preselected value while operating in the second mode. Converter efficiency is generated by computing a ratio of upstream sensor counts to downstream sensor counts during the test period.
21 Citations
11 Claims
-
1. A control method for an engine having a catalytic converter and first and second exhaust gas oxygen sensors respectively positioned upstream and downstream of the converter in the engine exhaust stream, comprising the steps of:
-
activating a preselected group of cylinders in a first engine operating mode and activating all engine cylinders in a second engine operating mode; providing a converter test period when a count in output transitions of the upstream sensor reaches a first preselected value while operating in said first mode and a count in transitions of the upstream sensor reaches a second preselected value while operating in said second mode; generating an upstream count by counting said output transitions of the upstream sensor during said test period; generating a downstream count by counting output transitions of the downstream sensor during said test period; and indicating converter efficiency from a ratio of said downstream count to said upstream count during said test period. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A control method for an engine having a catalytic converter and first and second exhaust gas oxygen sensors respectively positioned upstream and downstream of the converter in the engine exhaust stream, comprising the steps of:
-
activating a preselected group of cylinders in a first engine operating mode and activating all engine cylinders in a second engine operating mode; providing a converter test cycle when the engine has completed operation in a first plurality of inducted airflow ranges for at least a first minimum duration in each of said first airflow ranges while operating in said first mode and the engine has also completed operation in a second plurality of inducted airflow ranges for at least a second minimum duration in each of said second airflow ranges while operating in said second mode; generating each of said first minimum durations when a count in output transitions of the upstream sensor reaches a first preselected count while operating in each of said first airflow ranges of said first mode and generating each of said second minimum durations when a count in output transitions of the upstream sensor reaches a second preselected count while operating in each of said second airflow ranges of said second mode; generating an upstream count by counting said output transitions of the upstream sensor during said test period; generating a downstream count by counting output transitions of the downstream sensor during said test period; and indicating converter efficiency from a ratio of said downstream count to said upstream count during said test period. - View Dependent Claims (7, 8)
-
-
9. An electronic memory containing a computer program to be executed by an engine controller which controls an engine having a catalytic converter and first and second exhaust gas oxygen sensors respectively positioned upstream and downstream of the converter in the engine exhaust stream, comprising:
-
activation means for activating a preselected group of cylinders in a first engine operating mode and activating all engine cylinders in a second engine operating mode; test cycle means for providing a converter test cycle when the engine has completed operation in a first plurality of inducted airflow ranges for at least a first minimum duration in each of said first airflow ranges while operating in said first mode and the engine has also completed operation in a second plurality of inducted airflow ranges for at least a second minimum duration in each of said second airflow ranges while operating in said second mode; duration means for generating each of said first minimum durations when a count in output transitions of the upstream sensor reaches a first preselected count while operating in each of said first airflow ranges of said first mode and generating each of said second minimum durations when a count in output transitions of the upstream sensor reaches a second preselected count while operating in each of said second airflow ranges of said second mode; upstream count means for generating an upstream count by counting said output transitions of the upstream sensor during said test period; downstream count means for generating a downstream count by counting output transitions of the downstream sensor during said test period; and converter indicating means for or indicating converter efficiency from a ratio of said downstream count to said upstream count during said test period. - View Dependent Claims (10, 11)
-
Specification