Abstract: A method and apparatus for desulfating a NOx trap is proposed wherein the SOx purge temperature is achieved by modulating the amplitude of the A/F of the mixture supplied to the engine thereby storing oxygen in the trap during lean engine cylinder events and generating the required exotherm during rich engine cylinder events.

Abstract: A method and apparatus for desulfating a NO.sub.x trap is proposed wherein the SO.sub.x purge temperature is achieved by modulating the amplitude of the A/F of the mixture supplied to the engine thereby storing oxygen in the trap during lean engine cylinder events and generating the required exotherm during rich engine cylinder events.

Abstract: A method of monitoring hydrocarbons concentration in an exhaust gas includes the steps of: sampling exhaust gas on a vehicle, isolating the hydrocarbons from the exhaust gas on a vehicle, and measuring the amount of hydrocarbons isolated from the sample on a vehicle and providing an indication based on the amount of hydrocarbons. A sensor assembly for monitoring the concentration of hydrocarbons in an exhaust gas of a vehicle includes: a hydrocarbon absorbing material placed in a stream of gas on a vehicle, a gas sensor operatively connected with the absorbing material and in the stream of gas and producing a gas signal, and a sensor controller connected to the gas sensor for receiving the gas signal and for determining the amount of hydrocarbons.

Abstract: The invention is a nitrogen oxide trap comprising a porous support; and catalysts comprising platinum and lithium loaded on the porous support, the lithium being present in a high loading of at least 10 weight percent based on the weight of the porous support. The trap may be used in an internal combustion engine exhaust gas catalyst system. During lean-burn operation of the engine the trap sorbs nitrogen oxides (NOx) and releases the nitrogen oxides during decreased oxygen concentration in the exhaust gas, the desorbed NOx being converted to N.sub.2 and O.sub.2.

Abstract: An on-board monitoring system for estimating the hydrocarbon conversion efficiency of a vehicle catalytic converter receives temperature signals from a plurality of temperature sensors positioned to detect the temperature of exhaust gas entering the catalytic converter and to detect the temperature of the catalyst substrate in the catalytic converter at spaced positions along the direction of flow. Diagnostic routine initiation tests are performed to determine if the vehicle is operating within an acceptable range, and if so, then a plurality of sets of temperature values are measured and stored over a plurality of time intervals. During the time intervals, several engine operating parameters are checked to determine if the vehicle is operating within a range which conforms approximately to the range of operation encountered in the Federal Test Procedure (FTP).

Abstract: Methods and apparatus are provided for monitoring the performance of a hydrocarbon trapping device which removes hydrocarbons from an engine exhaust stream during cold startup conditions before the catalyst has reached its light-off temperature. The electronic engine controller which provides conventional fuel control functions is used to numerically integrate sensed values during a predetermined time interval in the engine's startup period. The sensed values indicate the rate at which hydrocarbons are being retained or purged by the trap, and the result of the integration indicates the total amount of hydrocarbon molecules trapped or purged. The integration result values may be retained for future readout during diagnostic procedures, and the result values may be compared with a threshold value to generate an alarm indication whenever the integration result value indicates that the trap is not performing satisfactorily.

Abstract: The invention relates to an improved emission control system. The system has particular applicability for use in an internal combustion engine (10) utilizing alternative fuels such as natural gas. More particularly, the invention provides an apparatus and method wherein hydrogen is removed by a conditioning catalyst (16) from the exhaust gas stream (21) to produce a conditioned exhaust gas (22). An exhaust gas oxygen (EGO) sensor (18) is in communication with the conditioned exhaust gas (22) and generates a signal in response to the sensed oxygen concentration of the conditioned exhaust gas (22). The A/F mixture entering engine (10) is adjusted by closed loop control means (14) in response to the signal generated by EGO sensor (18). The removal of hydrogen from the exhaust gas stream (21) eliminates lean shifts and allows oxygen sensor (18) and closed loop control means (14) to more accurately control the A/F ratio.