Method to reduce noxious components in the exhaust of internal combustion engines

Claim 1

Method to reduce noxious components in the exhaust of an internal combustion engine in which a reactor means (12) is provided to treat the exhaust gases, and a sensing means (13; 23, 33) is exposed to the exhaust gases and provides an output signal representative of the composition of the exhaust gases, said method comprising the steps of sensing the presence, or absence of free oxygen in the exhaust gases from the engine to obtain a measure of the composition of the exhaust gases from the engine before their liberation into the atmosphere; controlling the proportion of air and fuel ( lambda ) of the fuel-air mixture applied to the internal combustion engine to be below the stoichiometric value of unity ( lambda <1); introducing additional air into the exhaust gases before such liberation; controlling said introduction of additional air to the exhaust gases until the gases have a predetermined optimal relationship with respect to the stoichiometric value ( lambda 1); and further controlling the proportion of air and fuel ( lambda ) of the fuel-air mixture applied to the internal combustion engine in dependence on the sensed composition of the exhaust gases.