Diesel Particulate Filter (DPF)

What is a DPF?

A Diesel Particulate Filter (DPF) is a rigid filter located in the exhaust system of a diesel vehicle, designed to filter, and remove soot and particulate matter from exhaust gases. As part of the emissions system of your vehicle this component may over time become blocked or reach capacity and may need to be replaced. The main filter element comprises a ceramic or metallic element that exhaust gas passes through to catch the soot. Predicting when a DPF will fail is difficult as some may become blocked after 2-3 years of use whilst others will last the life of the vehicle.

Is A DPF The Same As A Catalytic Converter?

Both a DPF and a Catalytic converter (CAT) operate on the same principle of extracting contaminants from exhaust gases produced by your engine. A DPF however is specifically engineered to filter the soot from diesel exhaust gas but also have the ability to 'regenerate' periodically to burn the soot / carbon build up. Thus, allowing the DPF to continue to filter without becoming blocked. Modern diesel vehicles will have both a CAT and a DPF in sequence to allow the vehicle to meet emission standards (see image). The CAT will block the smaller contaminants whilst the DPF will trap the larger soot particles.

Why Is A DPF Important?

Some of the symptoms of a DPF that is blocked or not working properly are:

• Loss of power - As the filter becomes blocked and the exhaust gases push harder and harder to make their way through the DPF, the back pressure will cause the engine to exhibit a lack of power.
• Reduced fuel economy - Following on from a loss of power you would see a reduction in fuel economy based on having to push the engine harder to produce the same power.
• Poor throttle response - With the engine suffering from the inability to expel the exhaust gases effectively there would be an increased lag or sluggish throttle response when accelerating.
• Difficulty to start - Due to the build of carbon particles in the exhaust system this back pressure will in turn make the engine harder to crank over and start.
• Going into Limp Mode - Limp mode is enabled by the ECU when the DPF becomes so blocked, that to minimise any further damage the engine decreases performance to only allow it to be driven slowly. This will also become apparent by the engine warning light becoming illuminated on the dashboard.
• Bad exhaust smell and increased black smoke - Increased fuel consumption from a blocked DPF will lead to both an increase in unburnt fuel and also increased exhaust smoke.

How To Tell When A DPF Is Not Working Properly?

As the DPF is just one component in your vehicles emission system there are a variety of other parts that can fail, leading to check engine lights and / or blocked a DPF.

• Faulty EGR (Exhaust Gas Recirculation) valve – As exhaust gas is recirculated back through the intake manifold this can mix with any oil vapour that comes from the engine crankcase. Over time this mixture causes carbon build up inside the engine and this increased soot then passes through to the DPF, blocking the filter. As this is component is integral to the effective running of the emission system GOSS provide a wide range of replacement EGR valves
• Blocked fuel injectors – When fuel injectors become blocked or faulty, they can tend to provide an incorrect air and fuel mixture into the engine. By supplying too much fuel to the engine the unburnt fuel finds its way into both the catalytic converter and the DPF.
• Worn Turbocharger - If the vehicle is fitted with a turbocharger worn seals within the turbo can force oil into the exhaust manifold and block the DPF.
• Worn Engine - Diesel vehicles with high mileage could be expected to have a higher rate of DPF failure due to increased oil blow by from worn piston rings, weathered oil seals and contaminant and carbon build-up over time.
• Incorrect Engine Oil - Using engine oils that are not specifically formulated for diesel engines. Due to the incidence of carbon build-up on diesel engines, vehicle manufacturers specify engines oils that are compatible with the nature of diesel combustion.
• Blocked sensors or ECU fault – With a number of sensors being utilised to activate ‘regeneration’ cycles and other important functions these all need to work correctly to facilitate the running of the emission systems.

As can be seen, these are just a few of the symptoms and issues that contribute to a DPF becoming blocked or not running efficiently. It is important to run through a checklist of possible issues and faults in order to effectively diagnose where the initial cause of the blocked DPF has stemmed from. Failure to diagnose and rectify any of these primary issues can see the new replacement DPF suffer the same fate as the blocked DPF.

How To Maintain Or Regenerate Your DPF?

One of the best methods to maintain and prolong the life of your DPF is to ensure that it regularly gets to a hot enough temperature to actively burn off the soot and contaminants. The easiest way to do this is to drive longer distances than your usual day to day commute or when stuck in stop / start traffic. Take the car for a drive on the freeway at the speed limit and drop down a gear or two to bring engine revs up. Hold for 20-30 minutes and this will assist the car to do a passive regeneration. If your vehicle is currently in limp mode, driving at sustained higher RPM will be your best chance of getting out of limp mode. If the issue remains use a diagnostic tool to read the error codes to ascertain further.

Using high quality fuels also contribute to greater service life of your DPF. Premium fuels contain additives and detergents that help burn off harmful particles and their continual use prolong the lifespan of a DPF. Repco also stock a wide variety of fuel additives, including DPF cleaners that can provide additional cleaning benefits to minimise carbon build-up.

nother important factor is to ensure you run your vehicle on the correct engine oil as specified by the manufacturer. Engine oils with low or mid SAPS (Sulphated Ash, Phosphorous and Sulphur) content are suggested as these contaminants are particularly damaging to DPFs and contribute to both breakdown of the internals and also excessive carbon build-up. The Penrite range of Enviro+ engine oils have been specifically formulated to minimise DPF contamination and blockage and are licensed as being compliant to use by a wide variety of automotive manufacturers.

Using a OBD2 diagnostic tool, with suitable DPF regeneration function can initiate a forced regeneration of a blocked DPF. During this process the car may take up to 45 minutes to run and increase the engine and exhaust gas temperature in an effort to hopefully burn any soot down to ash.

When To Replace A DPF

Due to the significant cost of these units, a replacement DPF should be the final step once all other avenues mentioned above have been exhausted.

When the time comes to replace your OEM Diesel Particulate Filter, Ryco now stock a range of replacement DPFs that are of OEM specifications and a direct fit to your vehicle. Produced to International standards, these are a cost-effective alternative to a DPF supplied by the vehicle manufacturer.

Utilising the correct weight of Platinum Group Metals (PGM), Ryco replacement DPFs are built to perform to OEM specifications for the life of the filter. As a DPF is a one-piece self-contained unit all Ryco replacement DPFs have been manufactured to attach to existing mounting points and flanges and will also comprise heat shields and bungs for sensors.