Seeking help on DPF regeneration, 1.6 TDI

[KingJ]

Hello, since recently I own a 2010 Octavia 2 FL with 1.6 TDI engine.

 

I'm new to having a diesel so I'm now learning how to take care of it. Especially that most of the week the car is used for short distances around the town, with longer ones once a week or two. 

 

So here's the thing. I got VAG DPF app, connects it with the  ELM327 adapter. Tells me that the DPF is 94% full (I guess that what it means), so I took the car to a highway hoping to initiate regeneration. I drove for about two hours. Nothing happened.

 

I maintained RPM around 2500-3000 (max 3500) for a long way. Nothing happened. No signs of DPF renegeration I could notice.

 

But in the VAG DPF:

During the trip the percentage in rose to 100%.

Soot mass calculated went from ca. 23 to 24g (measured 8,3). 

"Field regeneration request status" changed several times between 1 and 3 (I have no idea what that means)

 

The app gave some signs, a red icon next to the DPF image and some sound, so I guess it was signalizing something but I'm not sure what exactly. 

 

I drove like that for another half an hour and still I didn't notice anything else happening. As for the app the percentage didn't get any lower, it remained 100, soot mass calculated went even slightly higher, "distance since last regeneration" just went up.

 

So what do I do? Does it mean anything, should I force regeneration (and how becase so far I was unable to do so) or just leave it alone and wait untill the regeneration starts? 

 

[pikpilot]

2 hours ago, KingJ said:

During the trip the percentage in rose to 100%.

Soot mass calculated went from ca. 23 to 24g (measured 8,3). 

"Field regeneration request status" changed several times between 1 and 3 (I have no idea what that means)

 

The app gave some signs, a red icon next to the DPF image and some sound, so I guess it was signalizing something but I'm not sure what exactly. 

Here are some copies from the same app and the same CAYC engine in my car.

The first one is after my last regeneration. Note it says 82% full, oil ash residue 30 grams (44%).

 

The second picture (below) shows the previous test when the regen was interupted as I had arrived home. Note the red icon you mentioned which in my case indicated only partial regen. The field regen box shows a 10, which I guess means the same thing.

 

The third picture below shows a similar oil ash content to the first picture but 63% full

 

I too have a lot of short drives these days followed by an occasional long drive of around 200 miles+.

My conclusion is that oil ash residue that blocks the DPF and is the only thing you need to worry about. The soot mass is really an indication that another regen is going to me needed soon.

I tend to use the % bar only as a general guide. The three photos are in reverse sequence over a 2 year period.

 

If the DPF warning light (mine never has) comes on, the car manual says "To clean the diesel particle filter, the vehicle should be driven at an even speed of at least 60 km/h » at engine speeds of 1 800 - 2 500 rpm for at least 15 minutes or until the warning light goes out with the 4th or 5th gear engaged (automatic gearbox: position S) when the traffic situation permits it."  

When you tried a regen you may have had the revs too high. It needs high torque which is why it says less than 2500 rpm in 4th or 5th gear.

"Field regen is a process that can only be done by a garage as it can be a fire risk. Basicaly it means burning the soot away by changing the fuel ratio to increase the exhaust gas temperature.

 

Your post has reminded me that I need to check my DPF again as I have recently  had two injectors replaced and I want to know if it has had any effect on the DPF.

 

[pikpilot]

Just to show how confusing these results are, below is a picture produced later than the ones above and shows a % full line of only 16%.

As I said before, it is only the ash content which is a true indicator of the state of the DPF.

[KingJ]

19 hours ago, pikpilot said:

I too have a lot of short drives these days followed by an occasional long drive of around 200 miles+.

My conclusion is that oil ash residue that blocks the DPF and is the only thing you need to worry about. The soot mass is really an indication that another regen is going to me needed soon.

I tend to use the % bar only as a general guide. The three photos are in reverse sequence over a 2 year period.

 

If the DPF warning light (mine never has) comes on, the car manual says "To clean the diesel particle filter, the vehicle should be driven at an even speed of at least 60 km/h » at engine speeds of 1 800 - 2 500 rpm for at least 15 minutes or until the warning light goes out with the 4th or 5th gear engaged (automatic gearbox: position S) when the traffic situation permits it."  

When you tried a regen you may have had the revs too high. It needs high torque which is why it says less than 2500 rpm in 4th or 5th gear.

"Field regen is a process that can only be done by a garage as it can be a fire risk. Basicaly it means burning the soot away by changing the fuel ratio to increase the exhaust gas temperature.

 

Many thanks for your answers, unfrotunately I can't see the pictures.

 

My experience continues. Yesterday the regeneration started in the least convenient possible moment. I took the car for a ride but the process turned out to be excruciatingly slow. And the yellow DPF control light turned on about half an hour into the process.

 

After over an hour of driving around I had to interrupt it because I simply had no to time to continue. The light was still on. 

 

I went back later and drove for about two more hours. It finished on about 25% and somewhere over 6 soot mass calculated. The DPF light turned off. 

 

The indicator in the corner of the VAG DPF (which I guess shows the tempo of soot burning?) varied from ca -70mg/km to over -200. Very rarely reached -300 for short moments. RPM about 2300-2800 most of the time.

 

Altogether the regen lasted for over 3 hours to complete. 

 

Should it really go on that long? Is there something that could be done to make it faster?

 

Do I understand correctly that the oil ash level is the thing that does not lower down with regen and has to be cleaned mechaically when it gets too high?

[pikpilot]

2 hours ago, KingJ said:

Do I understand correctly that the oil ash level is the thing that does not lower down with regen and has to be cleaned mechaically when it gets too high?

That is correct. It shows how full the DPF is. What was your final oil ash weight in grams?

 

2 hours ago, KingJ said:

Altogether the regen lasted for over 3 hours to complete.......It finished on about 25% and somewhere over 6 soot mass calculated.

Looks like you have done it and now have a good DPF. Well done

 

The way this forum handles pictures means sometimes the pictures appear as pictures and sometimes as a long winded text link.

To see the later, click on the text then on the new black page that appears, click on the little icon in the centre. This will then show the picture as a picture.

What was your final oil ash weight in grams?

[KingJ]

56 minutes ago, pikpilot said:

That is correct. It shows how full the DPF is. What was your final oil ash weight in grams?

 

Looks like you have done it and now have a good DPF. Well done

 

The way this forum handles pictures means sometimes the pictures appear as pictures and sometimes as a long winded text link.

To see the later, click on the text then on the new black page that appears, click on the little icon in the centre. This will then show the picture as a picture.

What was your final oil ash weight in grams?

 

The oil ash is less than 5g.

 

From I've read this is a low amount, is this right? Considering the age of the car I'm guessing it was cleaned by the previous owner at some point (?) 

 

It still bogs me that it took so long... I mean is it really supposed to last over 3 hours or is there something wrong. 

 

I can see only links to the pictures but I can't open them - opens only a grey color with a "no entry" sign. 

 

 

[pikpilot]

With oil ash so low the DPF must have been cleaned or replaced before you got the car. My oil ash is around 33grams after 75,000 miles. Mostly fast roads/motorways with some city driving for the first 53,000 miles and mostly short trips with occasional 200mile fast roads.

Normally a regen only occurs on longer journeys and takes about 20-30 minutes but in your case it would appear your soot content was very high so it took much longer.

I will see if I can reload the pictures as pdfs.

 

[KingJ]

On 09/02/2024 at 18:03, pikpilot said:

Normally a regen only occurs on longer journeys and takes about 20-30 minutes but in your case it would appear your soot content was very high so it took much longer.

 

About that. Before the regen I tried to trigger regeneration but was unable to do so, despite it being pretty full of soot already. It didn't start regen before the percentage in the app raised over 100%. 

 

Should it be possible to force regeneration by driving at the right speed and RPM even at a lower soot content, or it will only start regen when the soot contet gets high enough? Basically - am I on the car's mercy as to when it triggers the regen, or can I make the regen happen when it's convenient for me? 

 

[pikpilot]

There are a number of conditions that must be met before regeneration can start. I can't remember them all off hand but apart the revs and load mentioned before, it includes oil temperature, water temperature, DPF temperatute and more than a certain amount of fuel in the tank.

The basic trigger is high soot content. You can't burn soot to create ash if there is not enought soot there. Then you have to wait for for the other conditions to be met.

There was a good video by VAG a few years ago explaining the process. Anyone got a link?

[J.R.]

All these oil ash figures are simply fantasy, the ECU cannot measure it, it can only estimate what it thinks it might be.

 

You can even reset it to zero using VCDS without getting your hands dirty.

 

The only figure that I keep an eye on is the DPF differential pressure, that is an actual reading, I study it in conjunction with the soot mass which is another fantasy calculated figure but if its close to zero then the vehicle has regenned very recently so any back pressure will not be caused by the soot.

[KingJ]

That makes sense. I recently had another regen and if I took to VAG DPF at its word, it started completely out of nowhere. The app showed soot mass calc ca. 16, the percentage thing about 60% and suddenly it just magically jumped to over 24g and 100% respectively and the regen happened. This time it went a bit faster, took about an hour. Happened about 700 km after the last regen, and after about 250 km drive