The computer receives signals from a lambda probe, which is installed on the exhaust pipe or exhaust manifold of the engine and is constantly blown by the flow of exhaust gases. The lambda probe produces a voltage, the value of which is proportional to the residual oxygen content in the exhaust gases, and the computer, in accordance with this value, adjusts the ratio "air/fuel" in combustible mixture. This is necessary for two reasons: firstly, the mode of operation of the engine is constantly changing (idling, "full throttle" etc.); secondly, afterburning occurring in the catalyst is possible only with a certain amount of fuel in the exhaust gases.
Post-combustion occurring in the catalyst at temperatures from 300°C to 800°C, requires more than conventional combustion, the fuel content in the combustible mixture. Therefore, in vehicles with a catalyst, fuel consumption increases by approximately 5%.
The catalyst is installed instead of an additional muffler. It is a monolithic honeycomb structure, plated in platinum and rhodium. An elastic and heat-resistant wire mesh is used to secure the impact-sensitive ceramic catalyst housing.
Opel Vectra/Calibra vehicles use a three-way catalyst. This means that it controls three chemical reactions simultaneously: the oxidation of carbon monoxide (SO) and hydrocarbons (NS), as well as the reduction of nitrogen oxides (NOx).
Catalyst is also installed on 1.7 liter turbodiesel engines. In this case, it is an unregulated oxidation catalyst that neutralizes carbon monoxide (SO) and hydrocarbons (NS), converting them into carbon dioxide (SO2) and water (H2ABOUT).
Catalyst and exhaust gas recirculation
In the C16NZ and C18NZ engines, the content of nitrogen oxides in the exhaust gases is reduced even before the catalyst by means of a recirculation system. This system works as follows. An exhaust gas bleed valve installed on the engine intake manifold diverts part of the gases into the cylinders. In this case, the combustion temperature decreases, which means that the content of nitrogen oxides in the exhaust gases also decreases. The recirculation system is switched off at temperatures below +20°C by a thermal switch installed in the vacuum pipeline. The system does not require maintenance.
Rules for using a catalyst
To avoid failures in the operation of the lambda probe and catalyst, the following requirements must be met.
Gasoline engines
- Use only unleaded gasoline.
- When equipping the car with a catalyst, before installing it, fill the tank at least twice with unleaded gasoline and run it out while driving.
- Do not start the engine by pushing or towing. Unburned fuel at the time of ignition can cause the catalyst to overheat and fail.
- Avoid multiple starts of a cold engine. Unburned fuel accumulates in the catalyst and burns explosively as the engine warms up, causing damage to the catalyst.
- If you have difficulty starting the engine, do not keep the starter turned on for a long time. Find out the reason for the failure and fix it.
- Do not use chrome-nickel spark plugs, use only spark plugs with copper electrodes.
- If the ignition system fails, remove the fuel injection control relay or fuel pump relay until the cause is determined.
- Do not test for spark with spark plugs off.
- Do not check the operation of the engine by disconnecting the high-voltage wire from one of the cylinders.
- In the event of a malfunction in the ignition, reduce the number of revolutions and eliminate the malfunction.
- When filling in engine oil, in no case exceed the maximum level mark: excess oil will enter the catalyst as a result of incomplete combustion and can damage or completely disable it.
Gasoline and diesel engines
- Do not leave the car on dried leaves and grass. The catalyst is at a very high temperature, which may cause a fire.
- When filling in engine oil, in no case exceed the maximum level mark: excess oil will enter the catalyst as a result of incomplete combustion and can damage or completely disable it.
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