The exhaust gas catalytic converter has a stainless steel housing to which are welded inlet and outlet cones with pipes and mounting flanges, as well as heat reflectors holding the ceramic lining. The entire internal volume of the case is filled with a ceramic porous monolith or a wire mesh made of heat-resistant stainless steel, which are fixed with rings. The structure of the monolith is a conventional filter, the inner and outer surfaces of the pores of which, in contact with gases, are coated with a very thin molecular layer of an alloy of an active catalytic substance containing platinum, rhodium and palladium. The porosity of the monolith has a large surface area covered with this alloy of very expensive metals, which mainly determines the high price of the catalytic converter.
A reaction takes place in the catalytic converter that converts hazardous hydrocarbons and carbon monoxide in the exhaust gases into harmless gases and water vapour.
On vehicles with a catalytic converter, the fuel supply system is of a closed type, that is, based on a signal from a lambda sensor installed in the exhaust system, the control unit constantly optimizes the composition of the air-fuel mixture. Depending on the oxygen content in the exhaust gases, the lambda sensor induces a voltage of 0.1 V (high oxygen, lean mixture) up to 0.9 V (low oxygen, rich mixture). Based on this data, the engine control unit changes the opening time of the fuel injectors and changes the ratio of fuel in the air-fuel mixture. The stoichiometric ratio of the fuel mixture, at which its complete combustion occurs and there are no harmful substances in the exhaust gases, is 14.7 parts by weight of air per 1 part of fuel.
The catalytic converter works effectively at temperatures of +300... +800°C.
Operation of vehicles with a catalytic converter
The catalytic converter is a reliable and simple device that does not need any maintenance, but there are some facts that the owner should be aware of in order to maximize its life.
Do not use leaded gasoline in a vehicle equipped with a catalytic converter, as the lead will coat the precious metals in the catalytic converter, reducing conversion efficiency and eventually destroying the catalytic converter.
Always keep the ignition and fuel system in perfect order.
If misfiring is observed while the engine is running, do not operate the vehicle until the problem is corrected.
If the engine control warning lamp lights up while the engine is running, contact a service station as soon as possible. If there is damage to the engine management, then in addition to increasing fuel consumption and reducing the dynamic characteristics of the engine, the catalytic converter may fail.
Do not start the engine by towing.
Do not turn off the ignition at high engine speeds.
Do not use fuel or engine oil additives, as additives may contain substances that can damage the catalytic converter.
Do not drive the vehicle if a trail of blue smoke is visible from the exhaust pipe.
After stopping the engine, the exhaust system continues to emit a significant amount of heat for a long time, so you should avoid parking the car on grass and dry leaves.
Remember that the catalytic converter is fragile, so be careful not to hit it when removing the catalytic converter or exhaust system.
A catalytic converter used on a well-adjusted vehicle should last more than 100,000 km of the vehicle.
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