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Last time we had a general understanding of the development history of the three-way catalyst, so how does it work? Here is the answer for you.

To keep the Catalyst working efficiently,it's important to maintain the air fuel ratio close to the Ideal Balance.If it stays too rich or too lean for too long,the Catalyst won't be able to do its job properly.

When the engine runs with a slightly lean mixture it means there's more air than fuel.

This excess oxygen in the exhaust gases,can increase the production of nitrogen oxides while reducing the efficiency of the catalytic converter in reducing nox.However,the excess oxygen enhances the conversion of hydrocarbons and carbon monoxide into water and carbon.

Dioxide in general engines fitted with three-way catalytic converters are equipped with a computerized Clos Loop feedback fuel injection system,using one or more oxygen sensors placed in the exhaust system to measure the amount of oxygen present in the exhaust gases.

This information helps deter whether the air fuel mixture is rich or lean.The engine control unit ECU,receives signals from the oxygen sensors and adjust the rate of fuel injection into the engine.Accordingly this system helps three-way catalytic converters work well.

By maintaining a balance between rich and lean fuel mixtures,if the oxygen sensor detects a rich mixture or excess fuel,the ECU reduces fuel injection to lean out the mixture conver.

Firstly if the mixture is lean or has excess oxygen, the ECU increases fuel injection to enrich the mixture.By maintaining an ideal air fuel,ratio or oscillating slightly around it.The closed loop control system ensures that the catalytic converter operates at its peak efficiency on a modern diesel engine emission systems vary in arrangement.

Depending on the manufacturer and use case depending on the manufacturer and use case but always start with in cylinder,emissions reduction the most common form of in cylinder emissions reduction.

Is the exhaust gas recirculation system or EGR.

EGR works by returning a small portion of an engine's exhaust gas back to the engine's combustion Chambers through the intake manifold.Where it mixes with fresh air and fuel during the combustion process.This means that less oxygen reaches the cylinder less oxygen means a lower combustion temperature.

This way nitrogen oxide quantities can be reduced by up to 70%.As the higher the temperature the more harmful nitrogen oxides are produced in.Diesel engine cars the most commonly used catalytic converter is the diesel oxidation Catalyst.The catalytic converters used on gasoline cars won't work on diesel.Because the exhaust stream is different and expels a lot more unburned fuel and oxy in the exhaust. 

 Because diesel all run in a lean the diesel oxidation Catalyst doc works almost identical to gasoline engines.It is designed to oxidize carbon monoxide gasphase hydrocarbons and the sof fraction of diesel particulate matter to carbon dioxide and water.

These converters often operate at 90% efficiency,virtually eliminating diesel odor and helping reduce visible particulates."High-performance Diesel Oxidation Catalyst φ286mm Diesel oxidation catalytic -(DOC) Diesel vehicle exhaust gas pu – Kesairay"

A DOC (Diesel Oxidation Catalyst) is a critical component in the exhaust treatment system of diesel engines. It functions by oxidizing harmful pollutants in diesel exhaust, such as carbon monoxide (CO), unburned hydrocarbons (HC), and some particulate matter (PM), converting them into less harmful substances like carbon dioxide (CO₂) and water (H₂O). DOCs are an essential part of modern diesel vehicles to meet stringent emission standards.

These catalysts are neffective Ive for KNX,so nox emissions from diesel engines are controlled by exhaust gas,recirculation EGR.

The diesel particulate filter DPF positioned after the doc Catalyst,the DPF acts as a filter trapping and removing particulate matter like dirt and soot from the exhaust gases. 

So what is a diesel particulate filter? The next chapter will reveal it to you.