A DPF (diesel particulate filter) is a mechanism that captures and stores exhaust soot (diesel particles). This is in place to reduce emissions; however, their capacity is finite. As a result, the captured soot must be periodically emptied (burned off) to “regenerate” the DPF. This regeneration process cleanly burns off the excess soot deposited in the filter preventing the DPF from becoming blocked, reducing the harmful exhaust emissions, and fulfilling its role as an emissions control.
Method
There are two types of DPF burn off methods: passive and active.
Passive DPF Burn Off
In this method, the accumulated soot is burned off automatically without any external intervention when the vehicle is driven at high speed for an extended period. This high-speed driving creates enough heat to burn off the soot particles and regenerate the DPF
Active DPF Burn Off
In this method, the engine control unit (ECU) initiates the burn off process when it detects that the DPF is becoming clogged. The ECU adjusts the fuel injection timing, exhaust gas recirculation (EGR) rate, and air-fuel mixture to increase the exhaust gas temperature, which triggers the burn off process. This can be done through two methods:
Stationary Regeneration
The vehicle is parked, and the engine is revved to increase the exhaust temperature, which initiates the burn-off process.
On-Road Regeneration
The ECU will initiate the burn-off process while the vehicle is being driven. This is done by increasing the exhaust temperature to a level that triggers the burn-off process.
I want to point out that a trained technician should only do active regeneration, as improper execution can lead to engine damage and safety hazards.
Problems occur
Problems can occur with a Diesel Particulate Filter (DPF) due to various reasons, including:
Clogging
The DPF captures and accumulates soot particles, and over time, the filter can become clogged if not properly maintained. This can lead to reduced engine performance, increased emissions, and potential damage to the engine.
Regeneration failure
Regeneration is the process of burning off the accumulated soot particles from the DPF, and if the process fails, the filter can become clogged. This can occur due to faulty sensors, malfunctioning components, or a driving pattern that doesn’t allow for proper regeneration.
Faulty components
The DPF system consists of various components, such as sensors, pressure differentials, and valves, which can fail and cause problems with the system.
Fuel quality
Poor quality fuel can contain contaminants that can damage the DPF and cause clogging.
Incorrect usage
Driving habits such as short trips, low-speed driving, or idling for long periods can lead to incomplete regeneration and cause problems with the DPF.
The results
In Europe, the Euro 5 Standard forced the use of DPFs to reduce the amount of particulate matter in diesel vehicles. The previous standards were 80% (25 milligrams per km to 5 mg/km). As well as 28% for nitrogen oxide emissions equating to (250 mg/km to 180 mg/km).
(All figures mentioned may differ between vehicles; for vehicle-specific information, refer to the vehicle ownerβs manual or contact the manufacturer).