Dpf Regeneration - Explained

Jace

Sneaker Freaker
Found this on the AA website

http://www.theaa.com/motoring_advice/fuels-and-environment/diesel-particulate-filters.html

Diesel Particulate Filters (DPF)
Reducing diesel soot emissions by 80%

Changes to new car emissions legislation scheduled for 2009, the so-called 'Euro 5' standards, will make particulate filters as commonplace in diesel car exhausts as catalytic converters are on petrol cars.

The goal is an 80% reduction in diesel particulate (soot) emissions but the technology's not without problems – AA patrols are already being called to cars with the particulate filter warning light illuminated (indicates a partial blockage).

It's clear that changes to driving style may be required too for maximum benefit from these systems.

How do they work?
Diesel Particulate filters (DPF) or 'traps' do just that, they catch bits of soot in the exhaust.

As with any filter (think of the bag in your vacuum cleaner) they have to be emptied regularly to maintain performance. For a DPF this process is called 'regeneration' – the accumulated soot is burnt off at high temperature to leave only a tiny ash residue. Regeneration may be either passive or active.

Passive regeneration
Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Many cars don't get this sort of use though so manufacturers have to design-in 'active' regeneration where the engine management computer (ECU) takes control of the process.



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

It should be possible to start a complete regeneration and clear the warning light simply by driving for 10 minutes or so at speeds greater



Expensive repairs
If warnings are still ignored and soot loading continues to increase then the most likely outcome will be a new DPF costing around £1000.

Mainly town based driving
If your own car use is mainly town-based, stop/start driving it would be wise to choose petrol rather than risk the hassle of incomplete DPF regeneration.

DPF additives
The most common type of DPF features an integrated oxidising catalytic converter and is located very close to the engine where exhaust gases will still be relatively hot so that passive regeneration is possible.

There's not always space close to the engine though so some manufacturers use a different type of DPF which relies on a fuel additive to lower the ignition temperature of the soot particles so that the DPF can be located further from the engine.

The additive is stored in a separate tank and is automatically mixed with the fuel whenever you fill up. Tiny quantities are required though so a litre of additive should treat around 2800 litres of fuel, enough to cover 25,000 miles at 40mpg.

With this type of DPF regeneration will be initiated by the ECU every 300 miles or so depending on vehicle use and will take 5 to 10 minutes to complete. You shouldn't notice anything other than perhaps a puff of white smoke from the exhaust when the process is completed.

AA experience
We're seeing some evidence of these systems failing to regenerate too, even on cars used mainly on motorways. It seems that on cars with a very high sixth gear engine revs are too low to generate sufficient exhaust temperature. Occasional harder driving in lower gears should be sufficient to burn off the soot in such cases.

Check the handbook
If you buy a car with a DPF fitted it's important to read the relevant section of the vehicle handbook so that you understand exactly what actions to take if the warning light illuminates and how, if at all, your driving style may need to be adjusted to ensure maximum DPF efficiency and life.
 

OLDOILER

Full Member
Jul 28, 2005
1,292
1
Wiltshire, UK
Found this on the AA website

http://www.theaa.com/motoring_advice/fuels-and-environment/diesel-particulate-filters.html

Diesel Particulate Filters (DPF)
Reducing diesel soot emissions by 80%

A very useful thread and very true about not enough speed/heat when in 6th gear - I think this is just one of the many " technical advancements" thats has not been followed through in practise on the road, especially with av road speeds getting lower. .............................
 

PlatinumR

Arrived and lovin it!!
Jul 23, 2004
253
0
Shoreham-by-Sea
take note of these instructions if you have one - it's serious

our new work vans have these and they dont go above 20 and idle alot.

when these dpf get blocked theres a risk unburnt diesel can bypass the piston rings into the oil causing the oil level to rise followed by uncontrollable engine runaway till it dies or you can stall it - keeps running with keys OUT of the ignition.
This is Vauxhalls excuse after 5 of our vans self distructed!
We are looking at changing the fleet now, if we'd known the limitation of these we wouldn't have leased them in the first place
 

MatthewB

Active Member
Oct 14, 2007
75
0
I find it quite amusing that a device intended for environmental benefit may need to be driven at an increased speed in a lower gear to clean itself.
 

MikeShaw100

Leon FR - White Lightning
Aug 7, 2007
297
0
Wakefield
I like the statement in the leaflet that suggests you take an alternative (and obviously longer) route to allow DPF to regenerate :censored:

2400 miles on mine and warning light been on twice, despite 1800 miles being on motorwats at speed...

Mike
57FRTDi - Crono, 18", BT, Armrest, Alu, Muddies and Mats.
 

chrisboyle999

MFD3 for sale, inbox me.
Nov 28, 2006
1,838
0
Geordieland
sounds like an 'if your dpf requires replacing its driver error and nothing to do with seat so you have to pay for it yourself' get out clause to me.

btw, whats the pic of the cupra for???
 
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