Abstract: Method and system are provided for monitoring performance of a catalytic converter coupled to an exhaust of an internal combustion engine supplied with fuel from a fuel tank where the fuel can include a first fuel and second fuel in concentrations that vary from one refueling to the next. A ratio indicative of catalytic converter exhaust gas conversion efficiency is determined from signals provided by an exhaust gas sensor disposed upstream and an exhaust gas sensor disposed downstream relative to the catalytic converter, and a ratio threshold value indicative of a malfunctioning catalytic converter is adjusted in dependence on the concentration of one of the first fuel and second fuel in the fuel in the fuel tank.

Abstract: A method of detecting catalytic converter deterioration based on the ratio of the arc length or the number of transitions of signals from sensors upstream and downstream of the converter where ratio determination is restricted to predefined air mass ranges within corresponding predefined engine speed/load ranges in order to avoid areas of engine speed and load instability that might impair test to test repeatability of the deterioration detection.

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: EGR system for an internal combustion engine (105) comprises an EGR valve (150) disposed in an EGR recirculation conduit (125) involves estimating exhaust gas temperature at an engine exhaust manifold. An exhaust gas temperature drop between the exhaust manifold and the EGR valve is estimated and a time constant is determined that models the exhaust gas temperature as a function of EGR mass flow rate so that exhaust gas temperature at the EGR valve can be estimated by adjusting the estimated exhaust gas temperature at the exhaust manifold by the exhaust gas temperature drop and the time constant.

Abstract: A system and method for monitoring efficiency of a catalytic converter count switches of at least one upstream sensor interposed the engine and the converter and count switches of a downstream sensor, interposed the converter and atmosphere, during a definite time period after a switch of the at least one upstream sensor to account for propagation delay of exhaust gases traveling between the at least one upstream and downstream sensor. Upstream sensor switches may optionally be counted only if predetermined entry conditions are satisfied while downstream switches occurring during respective definite time periods after an upstream switch are counted without regard to the entry conditions. A switch ratio based on the number of switches of the at least one upstream sensor and switches of the downstream sensor is used to monitor conversion efficiency of the catalyst.