Vehicles with catalytic converter

Depending on the model and version, VW PASSAT vehicles are equipped with one catalytic converter. Gasoline engines with a catalyst must only run on unleaded gasoline. In the presence of a controlled catalyst, the system must also have a controlled mixture formation.

Controlled mixture formation can be performed by a carburetor or injection system, while the fuel-to-air ratio can constantly change depending on the condition of the car and the oxygen content in the exhaust gases. It is impossible to provide such mixture formation using a conventional carburetor, since it does not have an appropriate control system. For this reason, specialists resort to either electronically controlled carburetors or injection systems. The mixture formation system receives control signals from an oxygen sensor, which is located in front of the catalyst or on the outlet pipe and is washed by the exhaust gas stream. The oxygen sensor is an electrical sensor that indicates the residual oxygen content in the exhaust gases through fluctuations in electrical voltage and allows you to draw conclusions about the composition of the fuel-air mixture. In a fraction of a second, the oxygen sensor can transmit a corresponding signal to the mixture control unit and thereby constantly change the quality of the mixture. Firstly, it is necessary, as operating conditions are constantly changing (idle, full load), secondly, optimal afterburning in the catalyst occurs if there is still a sufficient proportion of gasoline in the exhaust gases.


So, in order for afterburning to occur in the catalyst at a temperature of +300 to +800°C, the fuel-air mixture must contain more fuel than would be necessary for complete combustion. As a result, during the operation of the catalyst, an increase in fuel consumption of up to five percent should be taken into account.

The catalyst, which is widely used, is a three-component one. This means that in this catalyst, due to the regulation of the excess air coefficient, the oxidation of carbon monoxide is simultaneously carried out (SO) and hydrocarbons (CH), as well as a decrease in nitrogen oxides (NO_x).

For exhaust gas cleaning, gas turbine supercharged diesel engines with a displacement of 1.9 liters and a power of 75 and 90 hp. equipped with an adjustable exhaust gas recirculation system, as well as an oxidizing catalyst. This catalyst reduces the content of carbon monoxide and hydrocarbons in the exhaust gases.

The catalyst is installed instead of the pre-muffler under the bottom of the body. The catalyst consists of a honeycomb-shaped ceramic monolith coated with a layer of platinum or radium. An elastic and heat-resistant wire mesh is used to attach the shock-sensitive ceramic body.