The principle of operation of a catalytic converter (catalyst) (Mazda Familia BG)

Petrol models of MAZDA 323 can be equipped with adjustable or non-adjustable catalytic converter. Adjustable catalytic converter requires adjustable mixture former.

An adjustable mixture former is a carburetor or injection system in which the fuel-to-air ratio can be constantly changed depending on the operating mode and the oxygen content of the exhaust gases. This is not possible with the previous carburetor, since it does not have a corresponding control device. Therefore, either an electronically adjustable carburetor or a fuel injection system is used.

The control signals for the mixture generator come from the lambda probe, which is located in the front part of the system and is blown by the exhaust gas flow. The lambda probe is an electrical sensor that indicates the residual oxygen content in the exhaust gases in the form of electrical oscillations and allows us to draw a conclusion about the composition of the fuel-air mixture. In a split second, the lambda probe can send a corresponding signal to the control element of the mixture generator, thanks to which the optimal fuel-air ratio can be maintained. On the one hand, this is necessary, since the operating modes are constantly changing (idle, full throttle), on the other hand, because afterburning in the catalytic converter can only occur if there is a sufficient amount of gasoline in the exhaust gases. Thus, in order for afterburning to occur in the catalytic converter at a temperature of +300°...+800°C, it is necessary that the fuel-air mixture contain more fuel than in pure combustion.

A three-functional catalyst is used everywhere. This means that with such a catalyst based on lambda regulation, the oxidation of carbon monoxide (CO) and hydrocarbon (HC) is carried out simultaneously, as well as the reduction of nitrogen oxide (N0x)