| 摘要 |
An exhaust system for a vehicular lean-burn internal combustion engine includes a NO<SUB>x </SUB>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 NO<SUB>x </SUB>in the exhaust gas.
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