Depending on the model and composition of the equipment, cars are equipped with catalysts. In the presence of a catalyst, the vehicle must be operated only on unleaded gasoline. If a variable catalyst is installed, a variable mixing device must also be provided.
Under the adjustable mixture preparation device in technology is meant a carburetor or injection system, where the proportion of air and fuel can constantly change depending on the parameters of movement and the oxygen content in the exhaust gases. A conventional carburetor does not provide this, since there is no corresponding control unit. For this reason, either a carburetor with an electronic control system or an injection system is installed.
The mixture preparation device receives control commands from the lambda probe located in front of the catalyst or in the exhaust manifold, where it flows around the exhaust gases. The lambda probe is an electrical measuring sensor that detects the content of residual oxygen in the exhaust gases and converts it into electrical voltage and thus allows you to influence the composition of the air-fuel mixture. In proportion, information about the oxygen content is transmitted from the lambda probe to the control unit of the mixture preparation device, which provides for constant regulation of its composition. On the one hand, this is necessary because the regimes are constantly changing (idle, full throttle), and on the other hand, also because the burning of the fuel in the catalyst occurs only when the exhaust gases contain sufficient for gasoline. Thus, in order for the afterburning of the fuel to occur in the catalyst at temperatures above 300°C., the proportion of fuel in the air-fuel mixture must be higher than that required for clean combustion. Thus, when operating a controlled catalyst, an increase in fuel consumption of about 5 percent should be expected.
The catalyst of common use is the so-called ternary catalyst. This means that in such a catalyst, under lambda control, carbon monoxide is simultaneously oxidized (SO) and hydrocarbons (PC), as well as a decrease in nitrogen oxides (Nox).
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