Every thing You Need to Know About Diesel Particulate Filter

DPF stands for diesel particulate filter. It is an after-treatment device fixed in diesel vehicles that captures exhaust ash particles and other contaminants from the engine's exhaust gas. By capturing the contaminants, it reduces the release of harmful emissions from the engine.

The diesel particulate matter that the filtration system captures is also called “soot” (black carbon). DPF systems are standard today in both heavy-duty and passenger vehicles. As per the emission regulations, automobile manufacturers are required to develop a system to reduce emissions, which led to the application of the DPF system.

DPF was first used in non-road machinery in 1980 and became a part of vehicles in 1985. However, PSA Peugeot Citroen was the first company to make the DPF a standard feature in passenger vehicles in the year 2000.

Components of DPF Car

A diesel particulate filter consists of a wall-flow filter block, which is the primary system component. It is made from porous ceramic material with a honeycomb structure consisting of several small channels running parallel to each other.

The other components of the filtration system are:

• Electronic Control Unit

• Catalytic converter to assist the regeneration process

• Inlet and outlet pipes

• Catalyst coating of platinum or ceria

• A cordierite substrate or silicon carbide

The function of a diesel particulate filter is to trap soot from the exhaust gas that is produced in the engine. The exhaust gas is directed through a filter substrate which is a fine pore ceramic structure having porous walls.

Soot particles are caught or deposited on the porous walls while the gas escapes through the structure. There are various types of DPF, but the most common one is the cellular ceramic honeycomb filter.

It has channels fixed at alternate ends, and the soot particles are retained on the top channel walls. However, it is essential to mention that the DPF system has a limited capacity to hold the soot particles, which must be removed for the filter to work efficiently. The process of cleaning the filter is called DPF regeneration, which will be discussed in detail below.

There are various types of diesel particulate filtration systems in the market, which are as follows:

Ceramic Fibre Filters- As the name suggests, this type of filter is made from different types of ceramic fibres that can be combined to form a porous medium. Such filters can be moulded into different shapes and customised for different applications.

A ceramic filter can altogether remove carbon particulates, including those less than 100 nanometres. It can achieve an efficiency of 95% or more in terms of mass and 99% in terms of particle number.

The porosity of ceramic fibre filters can be controlled to produce high-efficiency, low flow, or low-efficiency, and high-flow filtration.

Silicon Carbide Wall Flow Filters- Silicon carbide is the second most popular material to be used in a DPF car. The melting point of this type of filter is very high (2700 degrees Celsius).

The cores of this type of filter look like catalytic converter cores, having alternate channels plugged. The plugs push the exhaust gas to flow through the wall while the soot particles are collected on the inlet face. The efficiency of the Sic wall flow filter is up to 95%, and the filtration band is broad, too.

Cordierite Wall Flow Filters- Cordierite wall flow filters are the most commonly used filters made with ceramic material. They possess excellent filtration efficiency and are inexpensive. However, this type of filter has the lowest melting point (1200 degrees Celsius). It is known to melt during filter regeneration if the filter is overloaded with soot.

Metal Fiber Flow Through Filters- The cores of such filters are made with metal and are entwined into a monolith. Electric current can be passed through the monolith to heat it for regeneration.

Since the DPF car filters the exhaust gas by preventing the soot particles from releasing into the air, the soot particles remain inside the filter. Only a regeneration process can burn off the soot particles. However, the regeneration process occurs only under ideal circumstances.

Factors such as vehicle speed, engine temperature, exhaust gas temperature, and vehicle RPM play an essential role in enabling regeneration. Therefore, any mechanical glitch in the car system can obstruct the regeneration process and cause the DPF system to fail.

Here are some of the causes that impact DPF regeneration:**

Lambda Sensor: Any damage to the lambda sensor can affect the regeneration process. The lambda sensor is a part of the emission system; hence, it plays a crucial role.

The Thermostat: A defect in the thermostat also hampers the DPF system, as the thermostat is necessary to reach the optimal engine temperature needed for regeneration.

Glow Plugs: During the regeneration process, the glow plugs are turned on. Hence, any fault in the glow plugs can cause DPF system failure.

DPF Sensors: The DPF system consists of various sensors that track its performance. Therefore, any damage to the sensors can lead to inaccurate readings and signals, causing the DPF to fail.

Using the Wrong Engine Oil: Vehicles with a diesel filtratre system must use the recommended engine oils. Using any other engine oil can disrupt the functioning of the filtration system.

Low- Speed Journeys:** For regeneration to take place, the engine must reach an optimal temperature. However, when you go on short-** distance drives at a low speed, the engine does not heat up sufficiently, which in turn does not burn the soot particles.

Low Revs: Driving at low revs is an ideal thing to do if you want to increase fuel efficiency. However, when you drive at low revs, the engine temperature warms up very slowly. It is one of the major causes of DPF failure.

Not Conducting Regular Checks: Conducting regular DPF checks is essential to know if the system is functioning efficiently. You must get your DPF system checked by a mechanic to know of any shortcomings that exist.

Signs to Watch Out For DPF System Failure

Let us tell you the ways to recognise a DPF system failure so that when you see the signs, you can take the corrective measures at the right time. The symptoms that indicate a clogged DPF system are easy to spot. They are as follows:**

Reduced Fuel Economy- When you notice a reduction in fuel economy, it is a sign that the DPF system is not working optimally. The main function of the DPF system is to retain soot particles and let out exhaust fumes.

However, when the filter is clogged, the exhaust fumes cannot escape quickly. The accumulation of exhaust gases affects the engine’s performance, and it uses up more power to release the gases.

Dashboard Light Warning- Vehicles are equipped with sensors to monitor the engine’s performance. If performance drops, the issue is reported to the vehicle's computer system, and an orange light blinks on the dashboard, signalling you about a problem.

Engine Fails to Start- When the exhaust gases are trapped inside the DPF system, the engine fails to start until the pressure is lowered. By refusing to start, the engine mitigates the damage to itself and the filtration system.

Turbocharger Issues- The gas trapped inside the filter has no place to escape. Therefore, it starts leaking through the turbocharger to get out, causing issues such as gas or oil leaks, etc.

In many cases, the DPF car can be cleaned, and it can start functioning smoothly. However, in some cases, it cannot be cleaned or may be damaged due to high heat or thermal events. If the DPF is damaged, you can replace it.

You can find out about the diesel particulate filter cost depending on the make and model of the car, manufacturer, and other factors.

For a fully functional and optimal DPF system, it is essential to ensure that it can regenerate itself. Self-regeneration of the filter system is the only way to ensure its health. There are two fundamental ways in which regeneration takes place: Passive and Active.

Passive Regeneration

Passive regeneration is an automated process that occurs when the engine reaches 350 degrees Celsius. At this temperature, the DPF car burns off the soot particles trapped inside.

Passive regeneration takes place at the desired temperature when the car is driven at a high speed during longer rides. The process begins and ends on its own without the driver noticing it.

Active Regeneration

When the filter is 45% full with soot particles, the active regeneration process begins. During this process, the engine management system in the car injects raw fuel into the diesel oxidation catalyst. (DOC)

Therefore, the exhaust temperature increases, creating optimal conditions for regeneration. Just like passive regeneration, active regeneration is an automatic process.

For this process to be completed successfully, the car must be driven for a longer duration at high speed.

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Can I drive if the DPF light is flashing in my car?

It is not recommended to drive the car when the DPF light is flashing as it is an indication of an existing problem. Driving the car may further damage the filter substrate.

Why is a DPF system important in cars?

The DPF car is essential as it traps soot particles and prevents them from releasing into the environment as it is harmful.

Which is the recommended fuel for cars with a DPF system?

You must opt for ultra-low sulphur diesel for cars with a DPF system. It is also recommended to avoid using contaminated fuels at all costs.