Abstract: An air/fuel ratio control method for an internal combustion engine corrects airflow prediction errors. The method compares the current airflow to the value that was predicted several events in the past and creates an error signal. Based on this error signal, the current fueling is adjusted. These two mixtures, with equally offsetting lean and rich air/fuel ratios allow the catalytic converter to operate at peak efficiency despite prediction errors.

Abstract: A catalytic monitoring method for an engine having two engine banks of which each coupled to one of two catalytic converters using first and second exhaust gas oxygen sensors, respectively upstream and downstream of one catalytic converter. Third and fourth exhaust gas oxygen sensors are respectively coupled upstream and downstream of the other catalytic converter. Switch ratios are determined for each of the engine banks based on the switching ratios of each upstream and downstream pair of exhaust gas oxygen sensors. A combination of the switch ratios is used to determine overall catalytic converter system performance.

Abstract: An adaptive catalytic monitoring method for an engine having two engine banks each coupled to one of two catalytic converters uses first and second exhaust gas oxygen sensors respectively upstream and downstream of one catalytic converter. Third and fourth exhaust gas oxygen sensors are respectively coupled upstream and downstream of the other catalytic converter. Switch ratios are determined for each of the engine banks based the switching ratios of each upstream and downstream pair of exhaust gas oxygen sensors, with the switch ratio being adjusted by an adjustment gain that is a function of airflow and a catalytic converter characteristic. A combination of the adjusted switch ratios is used to determine overall catalytic converter system performance.

Abstract: A method for controlling the air/fuel ratio of an internal combustion engine uses a manifold pressure sensor and an exhaust gas recirculation system having an orifice and a exhaust pressure sensor located upstream of the orifice. Both the manifold pressure sensor and the exhaust pressure sensor are sampled synchronously with a frequency proportional to the firing frequency of the engine and then filtered to eliminate unwanted frequencies. The sampled signals obtained then have the necessary bandwidth needed for closed loop control of the exhaust gas recirculation flow and engine air/fuel ratio control.

Abstract: An air/ratio control system and method for an internal combustion engine coupled to a fuel vapor recovery system simultaneously maps a difference between a desired air/fuel ratio and a measured air/fuel ratio to fueling errors and a purge vapor flow. This system and method maximizes the ability to purge the vapor recovery system while maintaining the ability to diagnose fuel errors.

Abstract: A throttle position system for an internal combustion engine. Included is a method for filtering a throttle position sensor using a maximum allowable rate of change based on factors such as, for example, physical driver limits or physical electronic actuator limits, for rejecting noise spikes. The filtered signal retains the necessary lead for use in air/fuel ratio control while eliminating problems associated with large noise spikes. Fuel is supplied based on the filtered throttle position and measurements from either a mass air flow sensor or a manifold pressure sensor.