What decides the DPF regen?

[SkodaNewb]

So I've asked similar before, but I still just don't quite understand. 

 

My VRS Diesel this week did 4 short trips (10/15 min) , when home and parked up the fans stayed on after. Presumably trying to regen. 

 

I then started a 45 min drive and the regen started 5 mins into the trip (I have vag dpf) finished in 15. Perfect. All nice and clean I thought! Sat /sun I then did 3 more trips about and hour each, quite fast drives covered about 120-150 miles. 

 

Today wife did a 10min trip and it's trying to regen on the drive when she's pulled up, is that just really unfortunate timing? I'm showing 38% oil ash residue at around 70k, so about half the life of the dpf I'd guess? I just assumed doing 3 pretty good runs would keep it happy for a bit! 

 

I've had the car 3/4 months and some times I don't notice regens for weeks, sometimes it happens like this, it's not really causing a problem but 150 miles seems quick to be regen after a good few runs. This is a typical weeks drive few short runs and then long runs Fri-Mon. 

 

Should I just stop worrying and let it do it's thing!?! 

[mosse85]

Hi,

 

I'm from Finland and this is my first post here. I'm driving Octavia 3 CUNA 2.0 Tdi RS. Does your car have 23AX campaing update done? This update affected my car DPF regeneration sycle to decrease. Before it was 440-470 km's (~273 miles)  after update 220-300 km's (150-180 miles). I bought obdeleven and began to monitor my dpf regenerations.

I'm thinkin my car produces more soot after the 23AX update and this makes calculated soot mass increase faster. When it reaches ~23.5 the regeneration starts.

 

My car has done now 131000 km's (81366 miles.) Oil ash mass is about 31 grams if I remember correctly. So if your VRs has the 23AX done, Im thinking that 150 mile regeneration cycle is normal.

 

[Tivan]

From owning 1.6 TDI and actively tracking regens I can say it purely depends on type of driving you do. For my car, If I mostly do city its about 90 do 100 miles between regens. If I do highway, it can go 5 times as much without a regen on those speeds.

I just try to let it complete once I know its doing a regeneration. Of course, If I cannot and i need to park and stop I do it. But then on the next run I try to detour or something to let it complete. It's an annoyance, I agree, and one thing I am not going to miss when I change the car.

One thing I need to mention is, when I did not track regents like I do now and I did more interruptions, I had engine oil dilution and rise of oil levels. Since then I try to keep things under control. My DPF seems fine, but bloody diesel in oil is something I don't want.

[Tivan]

2 minutes ago, mosse85 said:

Hi,

 

I'm from Finland and this is my first post here. I'm driving Octavia 3 CUNA 2.0 Tdi RS. Does your car have 23AX campaing update done? This update affected my car DPF regeneration sycle to decrease. Before it was 440-470 km's (~273 miles)  after update 220-300 km's (150-180 miles). I bought obdeleven and began to monitor my dpf regenerations.

I'm thinkin my car produces more soot after the 23AX update and this makes calculated soot mass increase faster. When it reaches ~23.5 the regeneration starts.

 

My car has done now 131000 km's (81366 miles.) Oil ash mass is about 31 grams if I remember correctly. So if your VRs has the 23AX done, Im thinking that 150 mile regeneration cycle is normal.

 

Same for my car. It went from about 250 to 300 kms to 150. I mentioned this to a dealer few times, they just ignore me. If I could restore old software I would.

[mosse85]

14 minutes ago, Tivan said:

Same for my car. It went from about 250 to 300 kms to 150. I mentioned this to a dealer few times, they just ignore me. If I could restore old software I would.

Yeah. I mentioned this to skoda dealer after the update. Answer was if there's no warning light and the car is running normal no actions needed. They refused to return the previous version of the ECU program because they "can't"..

I like the car but that 23AX campaign ruined it. Now I'm finally learned to live with it and going to remap Stage 1 tuning.

[J.R.]

7 hours ago, Tivan said:

Same for my car. It went from about 250 to 300 kms to 150. I mentioned this to a dealer few times, they just ignore me. If I could restore old software I would.

 

I did! It cost a fair bit but was definitely worth it, what was really annoying me is that after having taken steps to reduce the excessive EGR and subsequent DPF sooting up to find that the DPF would regen at a very low mileage from a calculated soot level of 23g or whatever it was when the actual measured value was 3g 😒

[Tivan]

7 hours ago, J.R. said:

 

I to find that the DPF would regen at a very low mileage from a calculated soot level of 23g or whatever it was when the actual measured value was 3g 😒

If I may ask - how did you find that actual value? I would not be surprised if it's the same on my car. 

[CookieMonster87]

@SkodaNewb this is something I find frustrating about owning a modern diesel car and DPF anxiety.

 

I do a couple of 2 hour commutes a week mainly on A and B roads, the rest of the time the car is sat on the drive.
 

Did my usual commuting this week (again, a couple of hours on the road) with no obvious signs of a regen, took the dog 15 minutes up the road for a walk and when I turned the car off the fans were running accompanied by the smell of a regen.

Can’t see how it wouldn’t have got up to temp to have done a passive regen whilst on a 2 hour commute and yet it did on a 15 minute journey up the road.

[J.R.]

On 18/07/2023 at 07:07, Tivan said:

If I may ask - how did you find that actual value? I would not be surprised if it's the same on my car. 

 

VCDS

[classic]

I think I’m right in saying these engines will do a passive regen when the engine load and exhaust temperature is high enough.
They do an active regen when the ecu detects the soot level in the dpf is high enough to warrant it (I don’t know this value).

It monitors the driving style and exhaust temperatures and decides when the soot load could be high enough and does a regen. It also uses data from the exhaust pressures sensors, temp sensors and other ecu data to trigger an active regen. If it starts doing a regen it will be due to one of these two reasons.

[mosse85]

When the calculated soot mass reaches ~23.5 the regeneration starts

[CookieMonster87]

Had to do a couple of short runs this weekend already (no more than 15mins each) and my fan has been on every time i’ve stopped. I guess it isn’t completing the cycle in that short space of time.

 

Frustrating as, like I said, majority of my journeys are 2 hour commutes on A and B roads a couple of times a week but if the soot levels aren’t high enough it won’t start the cycle.

[J.R.]

Yes they do a passive regen but no the emissions fix ECU software takes no account of it.

 

I had done a 200 mile Motorway/autoroute journey back to back with a 500 mile autoroute journey towing a 3 tonne loaded large fronted removal trailer, large throttle openings the whole journey and high oil temperatures, 700 miles of non stop passive regen only for the car to try and fail to regen every day the next week on 20km journeys, and it did at least 2 active regens during the autoroute journeys because I logged them on the way back.

 

That was the final straw for me, I paid to have the software rolled back to pre emissions fix, I have heard the fans running but once in the last year when my stop coinicided with the automatic 1000km regen.