My Homepage

Diesel Particulate Filters (DPF) and the Environment

Diesel Particulate Filters (DPF) and the Environment

The aim is an 80% decrease in diesel particulate (soot) emissions, but the technology's not without issues; roadside assistance patrols are already being called to cars with the particulate filter warning light illuminated, which normally indicates a partial blockage of the DPF filter.

Undoubtedly, changes to driving styles might be demanded for maximum advantage from these emission-reducing systems.

How do the filters function?:

Diesel Particulate filters (DPF) or 'snares' do only that, they catch bits of soot in the exhaust.

As with any filter (think of the bag in your vacuum cleaner) they need to be emptied regularly to maintain operation. For a DPF this process is known as 'regeneration'; the collected soot is burnt off at high temperature to make only a miniature ash deposit. Regeneration might be either passive or active.

Passive regeneration

Passive regeneration occurs automatically on motorway-type runs when the exhaust temperature is not low. Many autos do not get this form of use though manufacturers have to design-in 'energetic' regeneration where the engine management computer (ECU) takes control of the process.

Lively regeneration

When the soot loading in the filter reaches a set limit (about 45%) the ECU can make modest adjustments to the fuel injection timing begin regeneration and to improve the exhaust temperature. If the journey's a bit stop/start the regeneration may not complete along with the warning light will illuminate to show the DPF is partially blocked.

It must be possible to begin a regeneration that is complete and clear the warning light simply by driving for 10 minutes dpf removal cost or so at speeds greater than 40mph.

Should you keep driving in a comparatively slow and blow off the light, stop/start pattern when you are able to expect to see other dash warning lights illuminate also. At this point driving at speed alone will not be adequate and also the auto might have to go to a dealer for regeneration.

Expensive repairs:

If warnings continue to be ignored and soot loading continues to raise then the most likely result will be a new DPF.

Largely town established driving:

If lease automobile use or your own auto use is primarily town-established, stop/start driving it'd be wise to select petrol rather than risk the hassle of DPF regeneration that is incomplete.

DPF additives:

The most usual type of DPF features an integrated oxidising catalytic converter and is found very near the engine so that passive regeneration is potential, where exhaust gases will still be comparatively hot.

There's not always space near the engine though some manufacturers utilize an alternate type of DPF which relies on a fuel additive to reduce the ignition temperature of the soot particles so that the DPF can be located farther from the engine.

The additive is kept in a separate tank and is mechanically combined with the fuel when you fill up. Tiny quantities are needed so a litre of additive should treat around 2800 litres of fuel.

You should not notice anything other than perhaps a puff of white smoke from the exhaust when the procedure is completed.

AA encounter:

The AA has seen evidence of DPF systems neglecting to regenerate - even on cars - which are used primarily on motorways. Their judgment is the fact that on automobiles with a very high sixth gear engine revs are too low to generate sufficient exhaust temperature, but occasional more challenging driving in lower gears ought to be sufficient to bum off the soot in such instances.

Check the handbook:

Should you buy or lease a car with a DPF matched it is important to read the related section of the automobile handbook so you realize exactly what actions to take whether the warning light illuminates and how, if at all, your driving style might need to be adjusted to ensure maximum DPF efficiency and life.