Catalyst warm-up assessment method for a motor vehicle catalytic converter

A method of assessing a catalyst warm up rate of a catalytic converter connected in an exhaust system of a motor vehicle internal combustion engine downstream of a first exhaust gas sensor and upstream of a second exhaust gas sensor, the method comprising the steps of:

• specifying a warm-up rate of said first and second exhaust gas sensors that is faster than a nominal warm-up rate of said catalytic converter;
• periodically measuring a first response rate of said first exhaust gas sensor and a second response raw of said second exhaust gas sensor during a warm-up period of said catalytic converter, and computing an oxygen storage characteristic of said catalytic converter based on a ratio of switching frequencies between said first and second exhaust gas sensors calculated over a predefined interval;
• determining an oxygen storage threshold corresponding to a minimum desired catalyst warm-up rate;
• and
• indicating that the catalyst warm-up rate is good if the computed oxygen storage characteristics is greater than the oxygen storage threshold, and that the catalyst warm-up rate is bad if the computed oxygen storage characteristic is less than the oxygen storage threshold.

A method of assessing a catalyst warm-up rate of a catalytic converter connected in an exhaust system of a motor vehicle internal combustion engine downstream of a first exhaust gas sensor and upstream of a second exhaust gas sensor, the method comprising the steps of:

• specifying a warm-up rate of said first and second exhaust gas sensors that is faster than a nominal warm-up rate of said catalytic converter;
• periodically measuring a first response rate of said first exhaust gas sensor and a second response rate of said second exhaust gas sensor during a warm-up period of said catalytic converter, and computing an oxygen storage characteristic of said catalytic converter based on said first and second response rates;
• determining an oxygen storage threshold corresponding to a minimum desired catalyst warm-up rate;
• indicating that the catalyst warm-up rate is good if the computed oxygen storage characteristic is greater than oxygen storage threshold, and that the catalyst warm-up rate is bad if the computed oxygen storage characteristic is less than the oxygen storage threshold;
• wherein an air/fuel ratio of said engine is controlled by a closed-loop control, and said first and second response rates correspond to output signal frequencies of said first and second exhaust gas sensors, respectively;
• and
• wherein said first and second exhaust gas sensors have respective first and second output signals that switch between high and low states in response to air/fuel ratios upstream and downstream of said catalytic converter, and said first and second response rates are measured by counting switching transitions of said first and second output signals over a predefined time interval.