What is a DPF on a diesel vehicle?

What is a DPF on a diesel vehicle?

DPF diesel car

In some circles, the term ‘dirty diesel’ is quite flagrantly used and, when getting down to detail, some could be forgiven for such an outlook. 

However, with the pursuit of cleaner and more efficient diesel engines, modern automotive technology has introduced various emissions control systems. One of the key components in this endeavour is the Diesel Particulate Filter (DPF).

The DPF plays a crucial role in reducing harmful emissions, but only when looked after properly – just as for parts such as the EGR valve, a DPF needs the proper maintenance and care to be able to do its job properly, or problems will arise.

What is a Diesel Particulate Filter (DPF)?

A Diesel Particulate Filter, commonly referred to as a DPF, is an emissions control device designed to capture and eliminate harmful particulate matter produced by diesel engines. 

Where the whole ‘dirty diesel’ conversation might come into play is when you consider the fine soot particles that are produced from a diesel engine as a byproduct of combustion, which can have adverse health and environmental effects.

A DPF is put in place to enable a combination of physical filtration and chemical processes to trap and burn off these particles, reducing emissions of particulate matter.

How Does a DPF Work?

DPFs are typically made of a ceramic or metallic honeycomb structure coated with catalyst materials.

As exhaust gases flow through the DPF, larger soot particles are trapped on the surface of the filter while smaller particles pass through. To prevent clogging, a process called ‘regeneration’ is initiated.

How DPF regeneration works

DPF regeneration is where the trapped particles stopped by the filter are burned off – there are two types of DPF regeneration: passive and active.

Passive Regeneration: this occurs naturally when the exhaust gases passing through the DPF become hot enough to burn off the accumulated soot. This process is more likely to occur during driving conditions where the vehicle’s engine has been able to generate substantial heat.

Active Regeneration: many will tell you that diesel vehicles require driving runs that incur both distance and speed so that the engine can operate at optimum levels. 

The DPF is one such component which benefits from such runs as, otherwise, active regeneration is needed when the engine is not able to get to a hot enough temperature. 

If the correct level of heat has not been reached, extra fuel is injected into the exhaust system, which raises the temperature within the DPF and burns off the trapped soot.

Maintaining a DPF

Like many such components, proper maintenance is essential to ensure the longevity and effectiveness of a DPF. 

  • Follow manufacturer guidelines: adhere to the manufacturer’s recommended maintenance schedule, as well as any specific guidance about using the vehicle.
  • Use high-quality diesel: try to choose a diesel fuel with low sulphur content, as lower-quality fuel can contribute to increased soot accumulation.
  • Regularly drive at highway speeds: it’s always advised that frequent highway driving can help a diesel run smoother, not least as maintaining higher exhaust temperatures aid in passive regeneration of the DPF.
  • Avoid short trips: following on from the above, short drives in a diesel don’t allow the DPF temperatures to get high enough to enable passive regeneration, and the engine’s systems have to take matters into their own hands.
  • Avoid engine modifications: your DPF’s performance will possibly be affected in a negative way if you make modifications to the engine.

Common DPF Issues and Solutions

It is still deemed wise to keep an eye on the performance of your diesel’s DPF, even if you are doing everything to keep it running at an optimum level.

  • Clogging: a DPF can become clogged with excessive soot buildup over time, especially if passive regeneration isn’t occurring frequently, and active regeneration might be required. If clogging persists, a professional cleaning or replacement may be necessary.
  • Failed regeneration: factors like faulty sensors, injector problems, or engine issues can disrupt the regeneration process. Diagnosing and rectifying the underlying problem is essential.
  • Ash accumulation: ash, a byproduct of engine oil combustion, can accumulate within the DPF over time. Unlike soot, ash cannot be burned off, and it requires periodic professional cleaning or DPF replacement.
  • Warning lights: if the DPF warning light on your dashboard illuminates, it indicates a potential issue. Ignoring this light could lead to reduced engine performance and increased emissions.

How long can you drive with the DPF light on?

As with any vital part, if faulty, it’s always going to be better to get it seen to sooner rather than later – and the DPF is no different.

When the DPF warning light comes on, it’s very possibly a sign that the filter is getting clogged with soot or ash and needs attention. When clogged, as the soot is not being burned off, this can often result in reduced engine performance, higher emissions, and possibly actual engine damage.

It could also be that, when the DPF light illuminates, your vehicle is attempting to initiate active regeneration to burn off the accumulated soot. To help in this scenario, where possible and legal, drive at higher speeds for a prolonged amount of time to engage passive regeneration, which is a much more efficient way of burning off the soot.

If the light stays on after this, however, then there could very well be an underlying DPF issue.