Abstract: An exhaust system for a vehicular lean-burn internal combustion engine includes a NOx reduction catalyst, a source reductant, means (20) for contacting the catalyst with the reductant, means for sensing the temperature of the exhaust gas and/or the catalyst bed and means, when in use, for controlling reductant addition. The reductant addition control means supplies an amount of reductant to the catalyst at a rate corresponding to a measured temperature value of the exhaust gas and/or catalyst bed, which temperature value has been pre-determined to correlate, in use, with an amount of NOx in the exhaust gas.

Abstract: An exhaust gas aftertreatment system for an internal combustion engine comprises a conduit for carrying a flowing exhaust gas, at least one filter for particulate matter, an oxidation catalyst for oxidising nitrogen monoxide (NO) to nitrogen dioxide (NO2) which catalyst is disposed upstream of the at least one filter, means for limiting flow of an exhaust gas in the conduit comprising a cut-off valve disposed in the conduit and control means selectively to operate the means for increasing the back-pressure thereby to increase the temperature in the system.

Abstract: A canister (1) contains a catalyst for generating NO2 and a filter (8) for trapping PM, e.g. from diesel engines. The filter is thermally isolated from the canister, and preferably is surrounded by an annular monolith comprising the NO oxidation catalyst or a SCR catalyst. The invention facilitates the combustion of PM even at low exhaust gas temperatures, in a compact device.

Abstract: A heavy duty diesel engine having an exhaust system incorporating a catalyst to convert NO to NO2 and a particulate trap on which soot particles are continuously oxidized, and a portion of the exhaust gases are recirculated through a cooler and exhaust gas flow valve before being mixed with air and fed to the engine cylinders. The system also incorporates a sensor to detect the amount of NOx in the exhaust to adjust the gas flow valve, thereby adjusting the portion of recirculated exhaust gas fed to the engine cylinders.

Abstract: A heavy duty diesel engine (1) has an exhaust system incorporating a catalyst (5a) to convert NO to NO 2 and a particulate trap (5b) on which soot particles are continuously oxidized, and a portion of the cleaned gases are recirculated through a cooler (7) and an exhaust gas flow valve (8) before being mixed with air and fed to the engine cylinders. Considerable reductions in NOx can be achieved.