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DPF and how it works

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AlanC

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I found this explanation of the function of the DPF on the T5 Oil Consumption Facebook page.
Makes a lot of sense, if you have had the problems I have experienced before the new engine was fitted.
Sorry it is a long item, but worth reading.

Alan


VAG DISESEL PARTICULATE FILTERS

Courtesy of David Bodily Volkswagen Technical Support Specialist

Diesel Particulate Filter (DPF)

Detailed below is important information outlining the function and features of the Diesel Particulate filter which all members of your team need to be aware of.

Diesel particulate filters are becoming more commonplace on diesel engines, particularly sizes 2.0L upwards. This is in order to reduce the exhaust emissions as required by European legislation.

The prime reason for a DPF is to reduce particulate matter entering the atmosphere. Particulate matter is found in the form of soot, which is produced during diesel combustion. The DPF traps most of the soot which would normally travel down the
exhaust and into the atmosphere. The DPF can hold a certain amount of soot, but not a huge quantity and therefore it needs to go through a process called ‘regeneration’ in order to clear the soot loading. When the soot goes through a ‘regeneration’ process it will be converted to a much smaller amount of ash. The ash is non-removable. There are two types of ‘regeneration’, passive and active.

During long motorway journeys, passive regeneration will occur. This needs no intervention from the engine control unit. Due to the raised exhaust temperatures on a long journey (temperatures between 350 and 500°C), the procedure occurs slowly and continuously across the catalytic-coated (with platinum) DPF. The catalytic-coated DPF is situated close to the Engine, therefore the exhaust gas temperature is high enough (500°C) to ignite the soot particles. Due to this soot is burned-off and is converted into a smaller amount of ash.

Active ‘regeneration’ is when the ECU intervenes when the soot loading in the DPF is calculated to be 45%. The procedure lasts for about 5 – 10 minutes. Specific measures are taken by the ECU to raise the engine exhaust temperature to above 600°C, these include switching off the exhaust gas recirculation and increasing the fuel injection period to include a small injection after the main injection. The soot particles are oxidised at this temperature.

The ECU will trigger a regeneration process, if for some reason this is aborted, ie. customer slows down, stops etc, the process will be resumed when regeneration conditions are once again met, above 60km/h (38mph). This will continue for 15 minutes.

If after 2 attempts of 15 minutes, a successful regeneration has not been possible, the loading will increase. At 50% soot loading, the ECU will continue to maintain maximum exhaust temperatures of 600°C to 650°C to cause a regeneration process. The system will try to run a regeneration process for 15 minutes. If unsuccessful, the system will repeat this process for a further 15 minutes, if still unsuccessful, the DPF light on the driver display panel will then be lit.

The owners handbook states, the DPF symbol lights up to indicate that the diesel particulate filter has become obstructed with soot due to frequent short trips. When the warning lamp comes on, the driver should drive at a constant speed of at least 60 km/h for about 10 minutes. As a result of the increase in temperature the soot in the filter will be burned off. If the DPF symbol does not go out, the driver should contact an authorised Volkswagen repairer and have the fault rectified.

At 55% soot loading the DPF light is lit on driver display panel. At this point the customer should follow the advice in the handbook. If they ignore this information and continue driving the vehicle until the soot loading reaches 75% without successful regeneration, additional warning lamps will light up. At this point the customer will also be complaining of lack of power, etc.

At 75%, regeneration is still possible with the use of the VAS tester. Only when the loading is above 95%, is it necessary to replace the DPF unit.

Operating Status System Response
45% DPF Load Level 1
- Normal Regeneration
50% DPF Load Level 2
- Regeneration at maximum exhaust
temperatures
55% DPF Load DPF lamp
Regeneration from 60 km/h
onwards
("See operating manual")
75% DPF Load DPF, SYS and MI lamp
Torque limitation, EGR
deactivation,
Regeneration via VAG tester only
95% DPF Load Replace the DPF Unit

The Warranty department has confirmed that if there is no fault on the vehicle and DPF regeneration has been unsuccessful due to the customers driving style and the
customers failure to comply with the instructions in the handbook, DPF replacement will not be paid for by warranty.

Common causes for complaint

• Frequent short journeys – Regeneration conditions are not met. Not recommended for sale in the Channel Islands and inner city driving.

• Customers who continue to drive the vehicle with DPF light on – Continued driving with the DPF light on and without successful regeneration results in excessive soot loading of the DPF, to a point where it is above 95% loaded. At this point regeneration is not an option and replacement of the DPF is
necessary.

• Fault 18434 particle filter bank 1 malfunction – Common fault code. This does not only relate to the DPF itself, but the entire exhaust gas handling system. This can be caused by defective temperature sensors, pressure sensors, additive
system components (if applicable), poor connections, wiring issues, etc.

Important Information

• Before diagnosing a problem vehicle or attempting to perform an emergency regeneration, it is important to obtain a full diagnostic log and read out relevant measured value blocks. These MVB’s contain important information on the condition of the DPF system and are essential in diagnosing the fault. When the DPF light is illuminated, it does not necessarily mean that the DPF requires regeneration. For further advice, please contact Technical Support with the information from the diagnostic log and MVB data.

• If a problem vehicle arrives with the DPF light, the engine management light and the emissions light on. If during your diagnosis and reading of relevant MVB’s, you find that the soot loading exceeds 75% (but is still below 95%), an emergency regeneration procedure must be performed with the VAS tester. Further to this, the customer needs to be educated. They need to understand why the lights have appeared on the dash panel. Their attention needs to be brought to the owners handbook instructions, so that they are aware of what the DPF light means and what to do when it appears. This should prevent unnecessary repeat visits for regeneration purposes.

David Bodily

Volkswagen Technical Support Specialist
 
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T6 CFO

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Thanks Alan, improved my knowledge. I knew about the dangers of repeated short journeys but this explains exactly why in relation to the DPF. I live in the City and my Cali is my only motor. It reinforces my current determination to only use the Cali for medium and long trips.


Mike
 
Teejay

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Thanks Alan, improved my knowledge. I knew about the dangers of repeated short journeys but this explains exactly why in relation to the DPF. I live in the City and my Cali is my only motor. It reinforces my current determination to only use the Cali for medium and long trips.


Mike
It's also another excuse to take it out for a longer run more often. I do 22 miles/ day but often go for an additional 20-30 mins down the road and then turn and head for home. Not always ideal as I often hit traffic but its a nice place to be so don't mind that much.

..me..
 
Lost Boy

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Excellent explanation, I always wondered why my light has never been on and now I know, lots of long Motorway trips ;)
Thanks
 
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AlanC

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Thanks Alan, improved my knowledge. I knew about the dangers of repeated short journeys but this explains exactly why in relation to the DPF. I live in the City and my Cali is my only motor. It reinforces my current determination to only use the Cali for medium and long trips.


Mike
A little run up to Gloucester services is all you need Mike.

Good coffee and a decent farm shop to boot. Worth the trip from Brssl.

Alan
 
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Mike
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A little run up to Gloucester services is all you need Mike.

Good coffee and a decent farm shop to boot. Worth the trip from Brssl.

Alan
I'll pick a nice morning and have a run up there.


Mike
 
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Mike
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Thanks Alan. Good to know. Seems the Adblue is quite a leap in lower emissions and higher power.


Mike
 
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AlanC

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It is interesting to note that reducing the NOx increases the soot and vice versa.
Ad Blue makes such a difference, as it eliminates the NOx.

Why do manufacturers stick with diesel engines for small vehicles? It makes sense for heavy goods, but not for cars or vans now, surely!

Alan
 
Loz

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It is interesting to note that reducing the NOx increases the soot and vice versa.
Ad Blue makes such a difference, as it eliminates the NOx.

Why do manufacturers stick with diesel engines for small vehicles? It makes sense for heavy goods, but not for cars or vans now, surely!

Alan
They probably aren't anymore but with many years in a development cycle these things take time to happen.
 
Digger

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Transporter as petrol outputs 210 CO2 and other pollutants and as my T6 puts out far less CO2 and the adblue effectively kills the NOx I know which I would choose. The Euro 6 with adblue does not increase the particulates either. Plus I am getting 39 to 41mpg as against the 24 mpg for the petrol. I will wait for a hydrogen fuelled Transporter as the hysteria around diesel will soon pass over to petrol as CO2 is the real baddie.
 
briwy

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Transporter as petrol outputs 210 CO2 and other pollutants and as my T6 puts out far less CO2 and the adblue effectively kills the NOx I know which I would choose. The Euro 6 with adblue does not increase the particulates either. Plus I am getting 39 to 41mpg as against the 24 mpg for the petrol. I will wait for a hydrogen fuelled Transporter as the hysteria around diesel will soon pass over to petrol as CO2 is the real baddie.

Can't agree with you here.
The diesel bashing is about particulates, not CO2 or NOX and I don't reckon it's going to go away.
 
Digger

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Can't agree with you here.
The diesel bashing is about particulates, not CO2 or NOX and I don't reckon it's going to go away.
I stand to be corrected but my information is that euro 6 diesels output similar levels of particulates as the petrol equivalent. The future is neither petrol or diesel and not electric unless we massively increase nuclear power. I think hydrogen may offer best option.
 
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WelshGas

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I stand to be corrected but my information is that euro 6 diesels output similar levels of particulates as the petrol equivalent. The future is neither petrol or diesel and not electric unless we massively increase nuclear power. I think hydrogen may offer best option.
Hmmm.
Hydrogen, and where do you get Hydrogen from? Electrolysis of water, which requires electrical power.
And where do you get the electrical power from to carry out the electrolysis to get the hydrogen to power your vehicle.
Oh and don't forget you have to make extremely strong storage systems for use on vehicles and mass storage will be in liquid form so that requires investment in large scale pressure vessels and large scale refrigeration, which requires electrical power which you get from ??

Electric or Hydrogen powered vehicles will never take over until the population embraces nuclear fission or fusion power.
 
Digger

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That is my issue as electric vehicles require mass battery sytems which create pollution problems in both manufacture and disposal. Unless some new form of battery is discovered hydrogen seems the lesser of two evils. I also believe that nuclear power will have to be considered as wind energy is unreliable for modern requirements. I don't have the answer but think better diesel technology will be here for some years to come.
 
sidepod

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All we need to do is crack the "hydrogen from sunlight" thing, nail world peace, eradicate religion and we're done. :bananadance2
 
Alan

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I couldn’t go fishing today so what better to do but revise on some of these past topics

My question is:-
Is it a cause of concern that I have only heard (don’t think I’m going def!) my regeneration management kick in once having done 8/10000 miles from new
My mileage to date is approx. 31000 mixed driving

Alan
 
Ocean Spirit

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Only you can answer that.
Do your typical journeys allow the engine to get up to temperature and allow your speed to be close to and above 40mph for 10 mins +?
If they do your DPF is probably in good shape.
 
Roger Boeken

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I found this explanation of the function of the DPF on the T5 Oil Consumption Facebook page.
What I don't read here is the regeneration cycle started even when you stand still and turn engine off without any light turning on at dashboard. This happened frequently during first year of ownership of myT6 , then I had a problem with engine management light on and I got a software update as part of a recall action (only done with cars that had the problem ) . After the software update I noticed the dpf regeneration while standing still occurs maybe once in 2 to 3 months (800miles or 1200km/month). I drive very economical and many short trips, longer trips only in the weekend and holidays. I don't know the price for a new dpf but I read in a German magazine that you can get it cleaned for +/- 350 euro. Not something to look forward to..
 

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