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With 26000 kms on my v8tdi now(my15) and a mates experience of going into limp mode due to clogged dpf at 50000kms it got me thinking what the soot and ash levels in my Touareg were.

So I ran a scan and the advanced measuring revealed the following.
This is after nearly 3.5yrs of ownership of a new Touareg with most of my driving around town and occasional freeway runs- once in few weeks.
I have never noticed a regeneration occurring over the years but the scan reveals it apparently happened recently.

Interested to know what levels of soot and ash others have and if anyone has noticed a regen.
In my mates case he was going interstate, had driven more than 500kms when then light came on and engine went into limp mode- had to be taken to a dealer for a forced burn. His use has been mostly around town until this trip.
So, what has your experience been and what readings do you have on your dpf?
 

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My understanding is that you will not get a complete burn if you run it always in town. So, this is probably what caused the eventual clog.

If you do not have a VCDS, it would be best to take take the vehicle for a minimum of a one hour long non-stop drive at least once every six months. That should give the system a chance to burn off properly.

Better yet, stop being cheap and buy a VCDS. Then post your driving style and your vcds scan to this thread.

Sigh has a great idea to collect data on this issue. The knowledge will help all the TDI owners take better care of their vehicles.
 

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I'm glad I deleted my DPF/SCR system, I don't have to worry about any of this bollocks.
 

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Here's some VCDS DPF data taken from my 2008 3.0Tdi

(If you look at the Adobe viewer 2 page view option it will make more sense)


TonyB
 

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Discussion Starter #5
My understanding is that you will not get a complete burn if you run it always in town. So, this is probably what caused the eventual clog.

If you do not have a VCDS, it would be best to take take the vehicle for a minimum of a one hour long non-stop drive at least once every six months. That should give the system a chance to burn off properly.
Well the confusing part is that he got his dpf clogged after 500kms of freeway driving.
Preceeding that was city driving mostly but one would think the freeway drive would help do a regen.

Would be good to hear from as many on their readings and experience.
Reading from mine doesnt look too bad given the split between city and freeway (much less)
 

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Discussion Starter #6
Here's some VCDS DPF data taken from my 2008 3.0Tdi

(If you look at the Adobe viewer 2 page view option it will make more sense)


TonyB
Thanks Tony

Big drop in the last two readings! Especially the Ash.
That cant be just from a regen? Did you get it professionally cleaned?
 

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Hi Singh,


Good pick up, the last reading is from my "new" '08 with 100K kms on the odo, all the other readings came from my previous one which had 220K on disposal in 03/2018, no maintenance ever done to DPF.


TonyB
 

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Well the confusing part is that he got his dpf clogged after 500kms of freeway driving.
Preceeding that was city driving mostly but one would think the freeway drive would help do a regen.
Yes, a long drive on a heavily loaded system can result in a trip to the dealer.

We need to find the VW theory guide on DPF to explain this. It has been a while since I read it, but basically the safety system kicked in to prevent an automatic burn.

This should be close to what happened. Read the theory guide if you want to get it 100% correct.

The system does not want the ash level to go over a certain percentage. If you do a lot of in town driving, you can go over that level.

All is not lost at that point, the system will still try to initiate a burn. A long highway trip is perfect and the burn is started. But, the computer monitors the burn temperature. The more ash you have to burn, the hotter the burn.

Once you hit a certain temperature, the system will shut down the burn.

All is still not lost. You are on a long highway drive and the system will cool down and a second burn will be attempted.

If this burns gets too hot, ie too much ash, this burn too will be aborted.

After a few burns (forget the exact number) the system will set a fault and no longer attempt to do anything.

At this point, you are supposed to take the vehicle to the dealer since you have a fault. The dealer computer will instruct the dealer to do on forced burn (forced regeneration) under controlled conditions. Not inside, not near any grass or vegetation, preferably parked over concrete.

If it is successful, you get the car back. If it fails, you get to purchase new exhaust parts.
 

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Googled it just for the fun of it. Note the part in bold. >:)

Regeneration while Standing/Idle

Prerequisites (General):

Ignition ON
Engine ON (Idle)
Fuel Tank at least 1/4 full
Transmission in Neutral/Park
Parking Brake engaged
Coolant Temperature above 70 °C (see MVB 002.4)
Particle Filter Load below Specification (see MVB 108.2/3 -or- 241.2/3 VCDS should give the specified values)

If the Particle Filter Load is above Specification the Particle Filter needs to be replaced since the car may burn down when regenerating.

Power Consumers ON (Light, Seat Heating, Front/Rear Window Heater, Climate Control)
Engine Hood Closed
 

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Discussion Starter #10
nickyt;2030705 We need to find the VW theory guide on DPF to explain this. It has been a while since I read it said:
Hi Nickyt,
Interesting, i am keen to get my hands on the theory/ details of dpf operation and regen, where can we find this?

Also, i thought its the soot that the regen burns and not the ash?
Ash, which is the result of dpf regens ie the burning of soot collected over time.
and ash cant be burnt, hence dpf’s have a life?
 

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Discussion Starter #11
Hi Singh,


Good pick up, the last reading is from my "new" '08 with 100K kms on the odo, all the other readings came from my previous one which had 220K on disposal in 03/2018, no maintenance ever done to DPF.


TonyB
That explains TonyB!
What was your driving style over the years? Freeway/city traffic split?
 

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The system does not want the ash level to go over a certain percentage.
That's soot, not ash. Ash level can only increase, never decrease, as that's the part that remains in the DPF after the it has been regenerated. If a regeneration completes, soot load is considered to have returned to 0%. However, ash levels never decrease, and when they reach a certain limit, the DPF is considered full/blocked and MUST be replaced. There's no other remedy for this.

Well, the DPF can be theoretically cleaned or even deleted, but this is not official repair method, and involves essentially the same process as the replacement of the DPF, except of course not every part of the DPF will be actually put back on or put back on new.

All is not lost at that point, the system will still try to initiate a burn. A long highway trip is perfect and the burn is started. But, the computer monitors the burn temperature. The more ash you have to burn, the hotter the burn. Once you hit a certain temperature, the system will shut down the burn.
It's not the temperature that stops regeneration - even though there might be fail safes for temperature, too. But generally a DPF regeneration, once initiated, should never reach temperatures that trigger such a shutdown - unless there's something wrong with the car. Instead there are two other things that can prevent or stop regeneration.

One of them is, that the cars cruising speed or the engine speed falls below a certain threshold (30-60 km/h, 1500-2000 RPM, depending on model), that's required for the regeneration. If this happens, this will not trigger a fatal condition per se, because the regeneration will be resumed when the car has speed up to required cruising speed again. The only problem that can arise from interrupted regenerations is, that soot still gets accumulated until it can be resumed, and trigger the other condition explained below.

The other condition that will prevent from the regeneration being initiated (or resumed) in the first place is, when the _soot_ levels are beyond a certain threshold. This might be 40 to 80% depending in the actual DPF. The regeneration will not be initiated because the burn temperatures would be too high in this case, and it could possibly result in the car catching fire or taking heat damage.

If this happens, but soot level is still below a certain limit (usually <75-80%) a manual regeneration can be initiated by service personnel through VAG-COM. Then they can monitor the process and abort if needed. However, if soot level goes above said limit, regeneration will not be allowed even this way, and the DPF will have to be replaced.
 

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The maximum allowed ash volume for that particular model (presumed it's a CATA engine) is 0.46. So, at 0.3 the DPF is already at 2/3 of its theoretical lifetime. Just FYI.

No, the engine is a CASA not that it would make any difference at it probably has the same DPF components fitted.


This is the first time that I have seen any ash levels quoted on the subject, do you have a reputable source for your quote?


thanks,


TonyB
 

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Discussion Starter #16
Thats what i understand. Soot is regenerated and results in ever increasing Ash.

Also, Whats the difference between calculated vs measured soot levels?
 

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Thats what i understand. Soot is regenerated and results in ever increasing Ash.
Correct.

Also, Whats the difference between calculated vs measured soot levels?
I think both of them are in a way calculated, but the "calculated" one is a rolling sum over time, that's based on fuel consumption, air intake, lambda measurement data, and calculates the theoretical amount of soot generated, while the "actual" value is calculated using the momentary difference in the exhaust gas pressure before and after the particulate filter. But don't quote me on that.

Anyway, I think it's kind of a self-check or fail-safe. The two soot load values are calculated using different methods, so that if the sensors involved in one start delivering false values, the ECU will notice the difference, and instruct the driver to have the vehicle serviced, and will refuse to start regeneration. This is likely important, because as said, starting regeneration on an "overloaded" DPF can cause the engine to catch fire - so, it makes sense to have the load value double-checked, just to be always on the safe side.

It might be also intended to prevent trivial tampering with the DPF (ie. delete).
 

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You guys have done some great work here. As I said, it had been a long time since I read the theory paper. As promised, it was sort of close. Thanks to all who filled in the gaps. :D

According to the SSP, there is a pressure sensor both before and after the DPF. There is also a temp sensor both before and after the DPF.

Here is a SSP guide that should help explain what is going on.

http://www.volkspage.net/technik/ssp/ssp/SSP_336.pdf

Frequent short trips
For the regeneration process to be initiated in the diesel particulate filter, the exhaust gas temperature is increased by the engine management system. In the event of frequent short trips, the exhaust gas temperature cannot reach a sufficient level. Regeneration cannot be carried out successfully. Subsequent regeneration procedures that are carried out with excessively high levels of carbon soot deposit can lead to overheating and damage to the particulate filter. The filter could become blocked due to a high level of carbon deposit. This blockage in the filter could cause the engine to fail.

In order to prevent these cases from happening, a diesel particulate filter warning lamp will be activated in the dash panel insert once a specific limit is reached in the filter storage capacity or after a certain number of unsuccessful regeneration procedures.

The driver is thereby requested to drive the vehicle at increased speed for a short period of time in order that the required exhaust gas temperature can be reached for purposes of diesel particulate filter regeneration.

The fuel quality
It should be noted that the quality of the fuel must meet the DIN standard as stipulated in the instruction manual. Operation with biodiesel is not possible. The extended injection period for regeneration of the diesel particulate filter can lead to unburnt fuel on the cylinder wall entering the engine oil from the piston movement. Normal diesel fuel vaporises itself out of the oil in normal operating conditions. Biodiesel cannot do this effectively due to its higher boiling point. The oil is thinned as a result, which can lead to engine damage.

If the fuel contains a high level of sulphur, this can lead to impaired function of the particulate filter system with higher fuel consumption as a result of increased regeneration.
 

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Discussion Starter #20
Good to have all this info and insights. All up I think vw have built a better system than other brands inc Land Rover.
I hear some horror stories from mates owning Range Rovers, Discovery sport models.

Would be great to have a DPF visual indicator, which similar to other meters shows on screen what the soot levels are all the time and helps avoid a build up/limp mode situation.
If after 500kms of driving post lots of city driving will not trigger a regen to clear it up there should be an indicator to help avoid the situation.

Other question is, can the dpf be professionally cleaned to get rid of the ash so its renewed again?
Vw charge about $200 for a reburn at the dealership and will only replace the dpf once its full.
I hear of dpf specialist workshops that service the dpf - using different methods of cleaning, here’s an example.
https://www.dpfcleaning.com.au/
Such companies apparently charge about $600 to renew the dpf and bring it back to life.
 
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