Updated at: 15-07-2022 - By: Lucas

It has become increasingly difficult for governments around the world to keep pollution levels in check, with the vast majority originating from automobiles. Carbon monoxide, nitrogen oxides, and hydrocarbons make up the bulk of these pollutants.

The National Emissions Standards Act for non-toxic emissions must be met by car manufacturers today. Emissions from your car are controlled by a catalytic converter, which is located in the exhaust system.

With this gadget, you can limit the amount of hazardous fumes and gases that are released from your car’s engine. Find out if diesel automobiles have catalytic converters and how they work.

So, Do Diesel Cars Have Catalytic Converters?


There is a catalytic converter in diesel cars, but it’s not the same as the one in gasoline or petrol-powered vehicles. Most diesel engines today feature four-stage emission controls. Recirculation of exhaust gas, DPF, DOC, and SCR are all examples of selective catalytic reduction (SCR). The DOC and SCR are two steps that are commonly referred to as catalytic converters because of their names. To reduce car emissions, they rely on catalysts, which facilitate chemical reductions.

The two-way catalytic converter is compatible with most diesel vehicles and engines. Carbon monoxide is converted to CO2 and hydrocarbons are converted to water and carbon dioxide in the two-way oxidation cat.

Modern automobiles are outfitted with the more cutting-edge three-way catalytic converters available on the market. DOCs are used to oxidize carbon monoxide in a two-way converter. The nitric oxide and nitrogen dioxide emissions, together referred to as NOx, are also reduced by an SCR reduction catalyst.

How Does A Diesel Catalytic Converter Work?

Do Diesel Cars Have Catalytic Converters

Toxic molecules are converted to harmless ones by the catalytic converter, which is a key part of the process. There are hundreds of tiny honeycomb-like cells inside its metal case, which is divided into two ceramic blocks.

Metals such as palladium and platinum are applied to the ceramic blocks. Toxic gases are converted into harmless byproducts before they are released into the atmosphere by the catalytic converter, which is located near the engine.

When it comes to operation, the Diesel Oxidation Catalyst (DOC) is nearly identical to that of gasoline engines. In order to reduce carbon monoxide to water and carbon, metal catalysts are used as catalysts in this process. By converting hydrocarbons and volatile wastes into less toxic chemicals, they also cut down on dangerous gas emissions.

There is no rhodium in the diesel-based catalytic converter, but it does have an associated diesel particulate filter (DPF) to remove particulate matter that is not present in the gasoline-based catalytic converter.

SCR, often known as DEF, is an ammonia-based catalyst that breaks down NOx emissions from vehicles and turns them into Oxygen and N2O. Water and nitrogen emissions are produced as a result of chemical reactions that occur when reductant and exhaust are passed over an SCR catalytic unit.

The open loop SCR system reduces NOx emissions by 75 to 90 percent. When it comes to stationary engines, a closed loop system has a 95 percent success rate. Eight percent of hydrocarbon emissions can be reduced using SCR, as well. Using low sulfur fuel can enhance its performance.

Diesel catalytic converter vs Diesel Particulate Filter (DPF)

Additionally, diesel engines converters are specially developed to target and filter particles from diesel engines. In addition to particulate matter and hazardous, unburned fuel vapor and gas, diesel engine emissions include a mixture of both. Soot and black smoke from diesel engines are common sources of these particulate matter particles. In industrialized cities, this frequently results in a brown haze.

There are three basic components of particulate particles. Solvent organic fraction (SOF), lubricating hydrocarbon (LHC), and hydrocarbon produced from gasoline are all examples (FHC). Particulate matter in the atmosphere has decreased over time as a result of the switch to low-sulfur diesel fuel. Sulphur-free fuel does not exist, and hydrocarbons still produce significant amounts of particulate matter.

Fortunately, because it is solid, particle debris can be filtered. A Diesel Particulate Filter (DPF) removes particles from diesel combustion pollutants before they are released into the atmosphere, much like a diesel catalytic converter. Among the components are metal fibers, silicon carbide, and cordierite in the form of a composite matrix.

How Long Does A Diesel Catalytic Converter Last?

Do Diesels Have Catalytic Converters-2

Diesel cats typically last for ten years or 100000 miles before needing to be replaced. However, the length of the journeys the vehicle takes will be a factor. The catalytic converter of a car that frequently makes stop-and-go excursions may wear out more quickly than that of a vehicle that travels for long periods of time.

Catalytic converters are unable to catalyze processes because they are turned off before they reach their optimal operating temperature range. Even while catalytic converters typically have a long lifespan, they still need to be checked for external and internal damage on a regular basis. It’s expensive to replace if it’s damaged.

What Are The Signs Of A Bad Catalytic Converter?

The accumulation of carbon deposits, for example, might cause a catalytic converter to malfunction over time, preventing the normal exhaust gas flow. Overheating, physical damage, and infection are a few other possibilities.

Signs of a catalytic converter malfunction include.

Oxygen sensors in modern cars flash up red if the converter isn’t working properly. A mechanical inspection is necessary if you notice any of these signs.


In cars, catalytic converters serve a critical role in reducing dangerous gas emissions. In addition to the catalytic converter, today’s cars are equipped with Ad Blue selective catalytic reduction technology, diesel gas particulate, and exhaust gas recirculation. Although it is important to have the cat checked out on a regular basis, it is not necessary.