Method and system for monitoring a catalytic converter

A system for monitoring exhaust gas conversion efficiency of a catalytic converter during operation of an internal combustion engine coupled to the catalytic converter, the system comprising:

• an upstream exhaust gas sensor interposed the engine and the catalytic converter for generating a first signal based on the exhaust gas upstream of the converter;
• a downstream exhaust gas sensor interposed the catalytic converter and atmosphere for generating a second signal based on the exhaust gas downstream of the converter;
• and
• a phase shift detector for estimating a phase shift between the first and second signals;
• a sampler for taking samples of the first and second signals;
• a processor, processing a portion of the samples of the first and second signals, such portion being a function of the determined phase shift to aligning the first and second signals such that the resulting phase shift between the first and second signals is substantially an integer multiple of π radians and for determining conversion efficiency of the catalytic converter based such phase aligned first and second signals.

A method for monitoring performance of a catalytic converter coupled to an exhaust of an engine using an upstream exhaust gas sensor disposed between the engine and the catalytic converter and a downstream exhaust gas sensor disposed between the catalytic converter and atmosphere, the upstream and downstream exhaust gas sensors generating first and second signals based on the exhaust before and after the catalytic converter;

• respectively, the method comprising:
• estimating a phase shift between the first and second signals;
• aligning the first and second signals such that the phase shift between the first and second signals is substantially an integer multiple of π radians;
• and
• determining conversion efficiency of the catalytic converter based upon such phase aligned first and second signals.

A method for monitoring exhaust gas conversion efficiency of a catalytic converter during operation of an internal combustion engine coupled to the catalytic converter, the system comprising:

• generating an upstream exhaust gas sensor signal based on the exhaust gas upstream of the converter from an exhaust gas sensor interposed between the engine and the catalytic converter;
• generating a downstream exhaust gas sensor signal based on the exhaust gas downstream of the converter from an exhaust gas sensor interposed the catalytic converter and atmosphere;
• estimating a phase shift between the upstream and downstream signals;
• sampling the upstream and downstream signals;
• processing a portion of the samples of the upstream and downstream signals, such portion being a function of the determined phase shift to align the upstream and downstream signals such that the phase shift between the upstream and downstream signals is substantially an integer multiple of π radians;
• and
• determining conversion efficiency of the catalytic converter based such phase aligned upstream and downstream signals.

A computer readable storage medium for use with an engine controller for monitoring performance of a catalytic converter coupled to an exhaust of an engine using an upstream exhaust gas sensor disposed between the engine and the catalytic converter and a downstream exhaust gas sensor disposed between the catalytic converter and atmosphere, the upstream and downstream exhaust gas sensors generating first and second signals based on the exhaust before and after the catalytic converter, respectively, the computer readable medium comprising:

• code estimating a phase shift between the first and second signals;
• code for aligning the first and second signals such that the resulting phase shift between the first and second signals is substantially an integer multiple of π radians;
• and
• code determining conversion efficiency of the catalytic converter based such phase aligned first and second signals.

A computer readable storage medium for use with an engine controller for monitoring performance of a catalytic converter coupled to an exhaust of an engine using an upstream exhaust gas sensor disposed between the engine and the catalytic converter and a downstream exhaust gas sensor disposed between the catalytic converter and atmosphere, the upstream and downstream exhaust gas sensors generating first and second signals based on the exhaust before and after the catalytic converter, respectively, the computer readable medium comprising:

• code for estimating a phase shift between the first and second signals;
• code sampling the first and second signals;
• code for processing a portion of the samples of the first and second signals, such portion being a function of the determined phase shift to align the upstream and downstream signals such that the resulting phase shift between the first and second signals is substantially an integer multiple of π radians;
• and
• code determining conversion efficiency of the catalytic converter based such phase aligned first and second signals.