Particulate filter – what is it and what is it for? Important information about DPF, GPF and FAP

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Artur Owczarek

Brand Product Manager Moje AutoHe has been involved in the automotive industry for years. He is passionate about cars and detailing. On his blog, he shares his knowledge and experience, offering tips on how to effectively care for your car and extend its life.

Why are particulate filters installed in cars?

Particulate filter? And what are these particles? Particulate matter is soot that is formed as a result of incomplete combustion of fuel. Due to their microscopic size, the particles can penetrate cell membranes. Soot is extremely harmful. It can penetrate the respiratory and circulatory systems and contribute to the development of cancer. A particulate filter can save us.

Soot is one of the components of smog. To reduce the amount of particulate matter in the air, increasingly stringent exhaust emission standards are being introduced. In the case of the Euro 4 standard, the permissible value of soot generated by a car has been reduced from 0,05 to 0,025 g/km. Starting from Euro 5, which came into force in 2011, the permitted emissions are 0,005 g/km. Currently, the obligation to reduce soot production also covers gasoline engines with direct injection. Previous restrictions applied to diesel cars.

Due to the need to adapt cars to standards, manufacturers began to use particulate filters. This is a solution that is designed to block soot before it escapes through the exhaust system.

What is the particulate filter used for?

The diesel particulate filter, or DPF (Diesel Particulate Filter), is a device that is part of the exhaust system in diesel engines. How does it work?

The stainless steel can contains a multi-layer body made of metal, non-woven fabric or (less often) paper. Thanks to the density of the channels, which are alternately closed on the inlet and outlet sides, a mesh is created. Blocking the channels means that when the engine is running, exhaust gases must penetrate the porous walls of the filter. During this process, particulate matter is deposited in the DPF. They are intercepted before exiting through the exhaust pipe.

The advantage of the filter is the reduction of emissions of harmful substances, the disadvantage is operation. Over time, the device becomes clogged. For this reason, it is necessary to burn the DPF. Cleaning involves heating the soot to a very high temperature, which can be up to 600 degrees Celsius.

When the DPF indicator lights up on the dashboard, we should go on a short trip. You may need to rev up and maintain a constant speed for a few minutes.

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DPF and FAP particulate filter – what are the differences?

DPF is a device used in diesel engines, which is a dry filter. French manufacturers, as well as brands using their drive units, often use wet filters called FAP (filter à particules).

What is the difference between DPF and FAP? The basic principle of operation is the same. Both devices are used to retain soot. In the case of FAP, the issue of burning the remaining particles was solved differently.

A special catalytic fluid is added to cars with a wet filter. When there is a need to get rid of soot, the substance is injected into the engine's combustion chamber. Thanks to the catalytic fluid, the temperature needed to burn soot is lower than in the case of DPF by 200-300 degrees Celsius. Thanks to this, filter regeneration is also possible on short journeys or while driving around the city.

DPF and GPF particulate filter – what are the differences?

The GPF filter (Gasoline Particulate Filter) is nothing else than the equivalent of the DPF filter for gasoline engines with direct injection. The main difference is the soot burning process.

In the case of diesel engines, the high temperature necessary to clean the filter is achieved by increasing the fuel dose. If the firing process is incorrect or interrupted, diesel fuel may penetrate into the lubrication system.

In the case of the GPF filter it is different. Gasoline engines produce exhaust gases at a higher temperature than diesel engines. To burn out the filter and increase the heat level even further, the fuel-air mixture is leaner. The filter cleaning process does not require traveling on the road. Much of the soot can be removed during normal operation.

Clogging of the particulate filter – how to clean it?

If we do not take care of regular burning of solid particles, it may have serious consequences. They may occur due to a clogged DPF filter problems with starting the engine or power loss. The unit may enter emergency mode.

Ignoring filter burn notifications or interrupting the procedure can cause unburned fuel to mix with the oil. In extreme situations and in the long term, this may lead to seizure of the drive unit.

What to do if the filter gets clogged? We can use it temporarily car chemicals. There are preparations that support the burning of the DPF filter. Most often, these are agents that are added to the fuel. We can also go to a workshop specializing in the service of restoring the efficiency of filters.

Is it worth regenerating the particulate filter?

Replacing a DPF or FAP filter with a new one is not cheap. The price of this component may range from approximately PLN 2000 to even PLN 15.

For this reason, a better solution may be to regenerate the DPF filter. In fact, it involves thoroughly cleaning this element from soot. The cost of such a service is approximately PLN 500. The price also includes the removal of the filter, but the final amount should not exceed PLN 1000.

Removing the particulate filter – what are the consequences?

Some drivers, wanting to avoid the costs associated with regenerating or replacing the particulate filter, decide to remove it. However, DPF removal is not a recommended practice. Firstly, it is an activity that adversely affects the environment.

Secondly, you have to take into account the consequences of removing the DPF. A car without a filter does not meet homologation and exhaust emission standards. If officers use a smoke meter during a road check and find that the car is technically defective, they may issue a fine of PLN 500. A vehicle without a particulate filter may also fail the technical inspection.

Severe penalties?

Work is underway to tighten penalties for vehicle owners who decide to remove them DPF. They can amount to several thousand zlotys. When looking for a used car, it is better to consider whether to buy a car with a removed DPF. Apparent savings may result in additional costs.

The particulate filter can be difficult to use, but its positive feature is the reduction in air pollution with carcinogens. It is worth burning off soot regularly and checking the condition of the exhaust system. We write more about how to take care of your vehicle, among others: in text How to take care of a car that is rarely used? What can break down when the car is parked for a long time?.