Abstract: An exhaust system for treating an exhaust gas composition having NO2 in a first NO2 concentration. The exhaust system includes a first catalyst that contacts a first portion of the exhaust gas composition converting it into a first oxidized exhaust mixture that includes NO2 in a second NO2 concentration that is greater than the first NO2 concentration. The system further includes a bypass that receives a second portion of the exhaust gas composition and a recombination section positioned downstream of the first catalyst. The first oxidized exhaust mixture is combined with the second portion of the exhaust gas composition to produce a first combined exhaust gas mixture. A second catalyst converts the first combined exhaust gas mixture to a second combined exhaust gas mixture having a third NO2 concentration that is less than the second NO2 concentration. The method used by the exhaust system is also provided.

Abstract: A method of reducing NOx in a vehicle exhaust operating by alternating exhaust flow between two lean NOx traps and directing the emerging exhaust to a downstream SCR catalyst system. While exhaust predominantly flows through one of the lean NOx traps, a reductant is provided to the other NOx trap so as to produce ammonia that is also directed to the SCR catalyst system. An exhaust system implementing the method of the invention is also provided.

Abstract: Ultrasonic detection of flaws in ceramic monoliths such as are commonly used in diesel particulate filters is made possible by beaming ultrasound into the monolith from an inlet or outlet face thereof and analyzing the reflected ultrasound from the same face. The monolith is preferably rotated during the scan, or the scan may be repeated from several rotational positions relative to the face of the monolith. Even small flaws which are hard to detect may be identified.

Abstract: An exhaust system for treating an exhaust gas composition having NO2 in a first NO2 concentration. The exhaust system includes a first catalyst that contacts a first portion of the exhaust gas composition converting it into a first oxidized exhaust mixture that includes NO2 in a second NO2 concentration that is greater than the first NO2 concentration. The system further includes a bypass that receives a second portion of the exhaust gas composition and a recombination section positioned downstream of the first catalyst. The first oxidized exhaust mixture is combined with the second portion of the exhaust gas composition to produce a first combined exhaust gas mixture. A second catalyst converts the first combined exhaust gas mixture to a second combined exhaust gas mixture having a third NO2 concentration that is less than the second NO2 concentration. The method used by the exhaust system is also provided.