Diesel Particulate Filters

Diesel Particulate Filters, or DPFs, are used to reduce the exhaust emissions of diesel vehicles and ensure that the vehicles are compliant with European legislation.
 

What Is A Diesel Particulate Filter?

DPFs dramatically reduce the amount of particles emitted from diesel engines by using a simple filter system. They trap approximately 85% of the soot that is produced during diesel combustion, rather than allowing it to travel down the exhaust and be released into the atmosphere.
 

Particulate Filters Must Regenerate

Just like with any other filter system, the filter itself must be cleared in order to continue working effectively. This is known as regeneration and occurs when the filter reaches a sufficiently high temperature, which allows the soot to be converted to a much smaller quantity of ash.
 
For the majority of systems, regular use of the engine at a sufficient speed will result in a high enough temperature of the exhaust gas to trigger regeneration. These high temperatures may result in a slight smell during regeneration, particularly during the first cycle.
 
In order to automatically regenerate the filter a vehicle must be driven at 50mph or above for at least 20 minutes, although this may vary from manufacturer to manufacturer.

What If It Doesn’t Regenerate?

If the vehicle is not driven in a way that triggers the regeneration process, the filter will become blocked. This will result in damage to the filter and will reduce overall vehicle performance. If the filter does experience a build up of soot, a warning light in the vehicle will alert the driver. Usually, the problem can be resolved by driving the vehicle in such a way that triggers the regeneration process; each vehicle handbook will have specific guidelines on how to do this.
 
In the event that it is not viable to drive the vehicle in a way that clears the filter - e.g. due to traffic conditions or speed limits – the vehicle can be taken to a dealership for forced regeneration.
 
Any damage to the vehicle that occurs as a result of failure to follow the regeneration process will not be covered by the manufacturer warranty package or the funder’s maintenance agreement.

Will These Vehicles Be Suitable For You?

Drivers operating in urban environments may not be best suited for vehicles fitted with a DPF, as these conditions may not allow for the vehicle to be driven in such a way that triggers the automatic regeneration process. Cars with diesel particulate filters are not recommended for those driving less than 5,000 miles per annum, or for those who drive in urban only driving conditions.

Alternatives For Urban Drivers

Most manufacturers fit their diesel vehicles with a diesel particulate filter that requires a high speed drive cycle in order to regenerate, although some manufacturers fit their vehicles with a self-heating particulate filter. Some will inject fuel straight into the filter, which burns and therefore increases the temperature in the filter. Others have heaters built into the filter.
 
Alternatively, a petrol, petrol hybrid, or electric vehicle may be more suitable for a driver operating only in urban areas.
 
All drivers must ensure that their desired vehicle is fitted with technology both suitable and appropriate for their driving conditions and requirements. If a vehicle with a diesel particulate filter is selected, the driver must ensure that the manufacturer recommended DPF regeneration program is adhered to.