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Types of catalytic converters

Types of catalytic converters

As many know, a catalytic converter is a part that can be found in a car’s exhaust system. Its primary purpose is to reduce air pollution by using its catalyst to start a chemical reaction. During that, poisonous and toxic gasses, such as carbon monoxide, are converted to less dangerous ones. Today, the primary standard is three catalytic converters: two-way, three-way, and three-way + air. They use a slightly different chemistry to reduce emissions, but their purpose stays the same. Long before honeycomb converters were found, there was another pelletized converter. It is usually found in older cars. But nowadays, their type usually differs for different kinds of vehicles.

As you can understand by its name, a two-way converter does two jobs simultaneously. First, its carbon monoxide is converted to carbon dioxide – this process is called oxidizing. Another one is when unburnt hydrocarbons are turned into water and carbon dioxide. By its design, all exhaust system gasses are sent through the converter, which contains platinum and palladium. Because even to start this chemical reaction, a high temperature is required. The gasses that come out of the converter are way hotter than those that come in. The biggest problem is that two-way converters can only work with lean fuel. Since its problems in ineffective control of nitrogen oxide emissions persisted, a more modern three-way converter was introduced.

Meanwhile, a three-way converter must do three jobs simultaneously. Like a two-way, it also oxidizes carbon monoxide and unburnt hydrocarbons. At the same time, it reduces the number of nitrogen oxides released into the atmosphere. The first three-way catalytic converter was introduced in the early 80s because of way more forced environmental laws by the US government. It is designed to work on gas, propane, and gasoline internal combustion engines that are started by spark ignition. By using it, carbon monoxide is reduced up to 95 percent and nitrogen oxide and hydrocarbons by 90 percent.

And, of course, there is a three-way + air converter that does the same tasks as the other two, but inside of it, there is an air pump. It pumps it back into the middle of the converter. Why does it help? Mainly because then oxidation capabilities are improved even more. Other than that, there is not much difference in its capabilities.

Do diesel engines have a catalytic converter?

The short answer is yes, they do. Since vehicles powered by diesel engines differ from gasoline, a different catalytic converter is required. Mainly because gas engines use a spark, and diesel ones use compression to start. This process requires a way higher air-to-fuel ratio to ensure ignition success. Those engines are usually more efficient than gas, but it comes with a price. This burning method produces way more emissions and more challenges to catalytic converters to reduce them. It usually lasts around 150 000 kilometers or, as one can say, ten years.

It doesn’t matter if it’s a petrol or diesel-powered car. It depends on your driving habits. Let’s say that a driver likes long trips; it would take more than 100k or 10 years to permanently damage it. If an owner does regular checkups, the catalytic converter should sometimes serve twice as much.