| abstract |
A method of and a system for cleaning exhaust gases from engines of motor vehicles, wherein the exhaust gases are passed through reducing and oxidizing catalysts so that nitrogen oxides are reducing in the reducing catalyst and carbon monoxide and hydrocarbons are oxidized in the oxidizing catalyst. The engines are so arranged as to be operable on a relatively thin mixture which is preferably proportioned to provide an excess-air ratio of about 1.0 to 1.15 so that substantially no carbon monoxide and hydrogen are present in the exhaust gases emitted from the engine. A reducing agent such as hydrocarbons is admixed to the exhaust gases entering the reducing catalyst for removing an excess of oxides and reducing the nitrogen oxides in the exhaust gases while secondary air is supplied to the exhaust gases entering the oxidizing catalyst for assisting in the oxidization of the carbon monoxide and hydrocarbons remaining in the exhaust gases passed through the oxidizing catalyst. |