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Diesel Particulate Filters (DPF) and the Environment

Diesel Particulate Filters (DPF) and the Environment

Clearly, changes to fashions that were driving might be demanded from these emission-reducing systems for maximum advantage.

How do the filters work?:

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

For a DPF this process is known as 'regeneration'; the accumulated soot is burnt off at high temperature to make just a miniature ash residue. Regeneration may be either passive or active.



Passive regeneration

Passive regeneration occurs automatically on motorway-kind runs when the exhaust temperature is high. Many cars do not get this sort of use though so makers have to design-in 'active' regeneration where the engine management computer (ECU) takes control of the process.

Active regeneration

It should be possible to begin a whole regeneration and clear the warning light simply by driving for 10 minutes or so at speeds greater than 40mph.

If you ignore the light and keep driving in a relatively slow, stop/start pattern soot loading will continue to build up until around 75% when you can expect to see other dashboard warning lights illuminate too. At this point driving at speed won't be adequate as well as the automobile might have to go to a dealer for regeneration.

Expensive repairs:

If warnings are still dismissed and soot loading continues to increase then the most likely result is going to be dpf failure a new DPF.

Chiefly town established driving:

If your own auto use or lease car use is chiefly town-based, stop/start driving it would not be unwise to select petrol instead of risk the hassle of DPF regeneration that is incomplete.

DPF additives:

The most common form of DPF features an integrated oxidising catalytic converter and is found quite near the engine where exhaust gases will be relatively hot so that passive regeneration is possible.

There is not consistently space close to the engine though some makers use another type of DPF which relies on a fuel additive to reduce the ignition temperature of the soot particles in order that the DPF can be found further from the engine.

The additive is stored in another tank and is automatically combined with the fuel when you fill up. Miniature amounts are needed though so a litre of additive should treat around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg.

You shouldn't detect anything other than perhaps a puff of white smoke from the exhaust when the process is completed.

AA encounter:

The AA has seen evidence of DPF systems failing to regenerate - even on automobiles - that are used primarily on motorways. Their conclusion is that on automobiles with a a sixth gear that is very high engine revs are too low to produce sufficient exhaust temperature, but occasional more difficult driving in lower gears should be sufficient to bum off the soot in such instances.

Check the handbook: