DPF Systems

Diesel Particulate Filter (DPF) Systems

A diesel engine produces diesel particulates, also referred to as soot particles, during normal operation. A Diesel Particulate Filter (DPF) is fitted in the exhaust system to filter soot out of the exhaust gases. Unlike a normal filter, the DPF has been designed to regenerate, or clean itself, to maintain operating efficiency. The process takes place automatically.

For the regeneration to occur, certain drive cycle conditions must be maintained. For example, if you drive only short distances, or frequently switch the ignition on and off, or your journey contains a high level of acceleration and deceleration, it’s likely your vehicle will have trouble completing the required parameters to achieve a DPF regeneration. This can result in a potentially costly DPF blockage and likely failure, which is very expensive.

It is advisable that you carry out occasional trips with higher vehicle speeds (such as on a highway, main road, or freeway) for a minimum of 20 minutes and avoid turning off the ignition but be sure to maintain engine speed at between 1500 RPM and 3000 RPM.

DPFs are filters and do not last forever. There is no prescribed service interval for DPF replacement and it’s likely that if you maintain the conditions to meet regeneration regularly, you will have many years of trouble-free motoring.

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.
• 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 becomes 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.