Functioning of the controlled catalyst (Mitsubishi Lancer 3)

COLT/LANCER engines have been equipped with an adjustable catalyst since September 1988 (and by special order since September 1986). An adjustable catalyst, in turn, requires the use of an adjustable mixture preparation method.

The variable mixture method refers to a specific design of the carburetor or injection device, in which the fuel-air ratio can always be changed depending on the driving conditions and the oxygen content of the exhaust gases. Previous carburetors did not provide this capability, since they did not have the appropriate control element. For this reason, engineers returned to the idea of an electronically controlled carburetor or injection device.

The mixer receives commands from the lambda probe, which is located in the muffler before the catalytic converter and is flown around by the exhaust gases. The lambda probe is an electrical sensor that converts information about the residual oxygen content in the exhaust gases into electrical oscillations and ensures the ability to correct the air-fuel mixture. In a fraction of a second, the lambda probe transmits the corresponding signals to the injection device control unit, which constantly monitors the air-fuel mixture. This is necessary, on the one hand, because the operating conditions are constantly changing (idle, full throttle), and, on the other hand, also because the gases are burned out in the catalytic converter if the engine exhaust still contains a sufficient proportion of gasoline.

In order for combustion to occur at all in the catalyst at temperatures from 300° to 800°C, the air-fuel mixture must contain a greater proportion of fuel than would be required for clean combustion.

The catalysts commonly used are so-called triple catalysts. This means that, as a result of lambda control, carbon monoxide (CO) and hydrocarbons (HC) are oxidized simultaneously, as well as nitrogen oxides (NO) are reduced_x).