What is a DPF or Diesel Particulate Filter? | Clean Air and low Emissions

Published Date: 27th Feb 2023

Image of a Car ExhaustA diesel particulate filter (DPF) is a device installed in diesel engines' exhaust systems to reduce particulate matter (PM) emissions and other harmful pollutants. The DPF traps soot and other particles produced during combustion and prevents them from being released into the air. DPFs work by using a combination of physical and chemical processes to capture and store particulate matter.

As exhaust gases pass through the filter, the particles are trapped on the filter walls. The filter then periodically undergoes a process called regeneration, which burns off the trapped particles and restores the filter's ability to capture more PM. Regeneration can occur either passively or actively. Passive regeneration happens when the engine reaches temperatures higher than 350°C. These temperatures allow the DPF to burn off the accumulated soot when the car is normally driven. Active regeneration involves using an additional fuel injector to increase the temperature of the exhaust and facilitate the burning of the trapped particles.

DPFs are commonly used in vehicles with diesel engines, such as trucks, buses, and some cars. They are also used in stationary applications, such as in diesel generators and industrial equipment. DPFs are an important tool for reducing the harmful emissions from diesel engines and improving air quality.

However, a rapid increase in fuel usage is one of the most obvious indicators of DPF failure. When the DPF is clogged, exhaust gasses cannot escape the engine as quickly as they should. The accumulation of exhaust gasses affects the engine’s overall performance, making it feel weaker. In this scenario, drivers typically hit the gas to increase the vehicle’s power. However, this tactic does not seem to help. Namely, the engine consumes more energy to eliminate the exhaust gasses from the DPF, which leaves less energy for acceleration.

To improve the health of your diesel particulate filter and increase its service life, you need to ensure it can regenerate itself when filled with soot. One of the greatest benefits of passive regeneration is that this is a fully automated process, but it is only possible when the engine reaches the required temperature, usually during longer rides and at greater speeds. When the soot levels in the DPF reach the limit of 45%, the pressure sensors register this. That is when the engine management system activates raw fuel injection to the diesel oxidation catalyst (DOC).

That way, it increases the exhaust temperature and creates the optimal conditions for active regeneration. Both passive and active regeneration requires the car to be driven for a longer time and at higher speeds.

The choice of low-quality engine oil is one of the major causes of DPF failure. Traditional engine oils use metallic additives that act as powerful anti-friction, anti-wear, and detergent agents. However, they can result in the creation and accumulation of ash, which blocks the substrate wall and prevents the uninterrupted flow of exhaust gasses.

Therefore, when choosing engine oil for a car fitted with a DPF, ensure it is safe. DPFs require the use of low-SAPS engine oils. These lubricants contain low Sulphated Ash, Phosphorous, and Sulfur levels and have a lower tendency for ash generation. Engine oils for diesel vehicles equipped with three-way catalytic converters and DPFs belong to the C grade. While C1 and C4 are low-SAPS oils, C2, C3, and C5 are mid-SAPS oils.

In addition to choosing the right engine oil, you can follow other maintenance tips to keep your DPF in good condition. One important tip is to avoid short trips whenever possible, as these do not allow the engine to reach the necessary temperature for passive regeneration. If you frequently make short trips, consider taking your vehicle for a long drive on occasion to allow for passive regeneration.

Another tip is to avoid using additives or fuel treatments that claim to clean the DPF, as these can actually cause more harm than good. The best way to clean the DPF is through proper regeneration processes.

If you notice warning lights on your dashboard related to the DPF, such as the DPF warning light or the check engine light, it is important to have your vehicle inspected by a qualified mechanic as soon as possible. Ignoring these warning lights can lead to more serious and costly damage to your engine and exhaust system.

In summary, the diesel particulate filter plays a crucial role in reducing harmful emissions from diesel engines. Proper maintenance, including choosing the right engine oil and following recommended regeneration processes, can help ensure the longevity and effectiveness of your DPF.

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Diesel particulate filters (DPFs) are devices that remove particulate matter (PM) and other harmful pollutants from diesel engine exhaust systems.

DPFs work by trapping particles produced during combustion and periodically undergoing regeneration to burn off the trapped particles.

Regeneration can occur passively or actively, with the latter involving an additional fuel injector to increase exhaust temperature.

Maintenance tips for DPFs include ensuring they can regenerate, choosing low-SAPS engine oils, and avoiding short trips or idling for extended periods.

Traditional engine oils with metallic additives can cause ash buildup and block the DPF substrate wall, so low-ash and low-emission oils are recommended for vehicles with DPFs.

Failure to maintain a DPF can lead to reduced engine performance, increased fuel consumption, and, eventually, DPF failure.