DPF Regen Query

[CookieMonster87]

Over the last 2 weeks I've noticed that my fan has remained on, on a couple of occasions, after the engine is switched off.

 

This has happened after my 20 odd mile commute in the morning which takes roughly 40 minutes on a mix of A and B roads. At this time of day it hasn't been overly warm however I usually have my aircon on at all times on auto.

 

I've only smelt the burning smell once which led me to believe the DPF was doing a regen. Other than that my MPG is usually between 47 and 52. I haven't noticed the revs sitting higher and I haven't had any codes or lights on the dash. 

 

Car was serviced and MoT'd by Skoda in June with no problems and I usually do a couple of longer runs a month.

 

Is this a sign of anything untoward? This is my first Diesel car so I'm not all that familiar with the DPF system, it'd be nice to have some kind of signal on the dash to show when it is carrying out a regen though.

[Jevpls]

Higher revs can be seen only when the car is on idle - you won't notice that while driving. Then you might see higher fuel consumption on the screen (for example, for my 2.0 TDI it might rise from 4,0 l/100km to 5,0).

Also ~1k rpm on idle doesn't mean DPF regeneration - it also happens on cold and hot weather as well.

No fault warnings will be shown if DPF manages to regenerate succesfully. I believe you can buy a OBDII bluetooth adapter and install some software in your phone to see DPF things.

[cmcm789]

My 1.6TDI will regen regularly. I don't do long journeys and find that if fully cleared it is good for another 400+ miles before it reaches the threshold.

 

I know when it's carrying out a regen when it is idling at 950/1,000rpm when it really shouldn't. Also, it gets very lumpy under acceleration especially at low revs (almost like dirt in fuel) as the car over fuels. And, the fan will be on after every journey.

 

If the car cannot sort itself out then you will get a light on the dash. Following a light coming on, car in limp mode and a £200 forced regen in the first few months of ownership, I invested in the OBDII Bluetooth adapter (£13 off ebay/ amazon) and the android app (about £3.00) so that I can keep an eye on it. It shows the level of soot in the DPF and loads of other details. When the level of soot reaches 88% the car will start a regen and the exhaust temp rises from 200 to over 500 degrees (when the car is up to speed). if at this point I drive for 6 or 7 miles at about 50-55mph in 5th gear the soot will burn off and the regen will cease at about 20-25%. Then I know I have another 400 miles before it happens again.

 

If the car reaches mid 90s% without successfully clearing itself then the light on the dash will come on. This used to happen me quite a bit.

 

If your car is in a regen and you stop or your speed drops it will stop the regen. With my car this was happening all the time (due to driving style) before I bought the adapter.

 

I would def recommend the app. Don't know why the dash display can't include this!.

 

One other thing to note and probably the most important is that you need about 1/4 of a tank of fuel to ensure the car will start the regen. As it is so fuel intensive it won't trigger with too little fuel. You won't know until the light comes on and even then if you drive the duration at the right speed, I don't think the car will get the exhaust temp up high enough. This is what happened my and it was a very expensive lesson.

[CookieMonster87]

@cmcm789

 

Thanks for the detailed reply, cleared up a few bits for me.

 

Can you help in explaining the following to me?

 

I took a 4 hour drive up to visit family for the weekend using a mix of A and B roads, dual carriageways and motorways. Then today I jump in the car to nip to the shops (10 minute drive) and when I get there the car is doing a regen.

 

I jumped out and noticed the fan running and a burning smell. I was surprised at this as I thought the journey would have been good enough to passively burn off soot on the long run the day before.

 

If not, then why wouldn’t it have done a forced regen then as opposed to me nipping 10 minutes down the road to the shop when I haven’t even exceeded 40mph?

 

No warning lights to speak of.

Edited 31 August, 2018 by CookieMonster87

[pikpilot]

Not unusual. Mine started a regen when I was using the gears aggressively around town, taking the rpm over 2500. Surprised it continued until I was home, as I was stopped at lights and roundabouts many times.

[Redfab]

Cookiemonster, you say it was serviced in June this year.  

It is possible that they have updated the software of your car to what they call the “fix” file to address the alleged cheating emissions software. 

This version of “updated” software actually puts all of the components of your engine under unnecessary extra stress and causes regens much more frequently and drastically reduces the life and reliability of your car. 

 

Has this behaviour been been a significant change from what you knew prior to the service?

 

The app Cmcm789 mentions is very good. It’s called vag dpf. Available on android only. You need an elm327 Bluetooth adapter for the obd port. I use the Carista adapter. 

 

I have a 1.6 Tdi cayc and use it all the time to know when to take the car for a short drive to allow it to Regen. It also tells you your software version. 

Edited 1 September, 2018 by Redfab
Typing error

[pastiche]

Quote

For give my ignorance but is a regen when the fan comes on when stopped, mine has been doing that quite often , had the fix last year. To get it back to normal do I just ask dealer or have to go through what has been said on here

 

[cmcm789]

On 31/08/2018 at 20:46, CookieMonster87 said:

@cmcm789

 

Thanks for the detailed reply, cleared up a few bits for me.

 

Can you help in explaining the following to me?

 

I took a 4 hour drive up to visit family for the weekend using a mix of A and B roads, dual carriageways and motorways. Then today I jump in the car to nip to the shops (10 minute drive) and when I get there the car is doing a regen.

 

I jumped out and noticed the fan running and a burning smell. I was surprised at this as I thought the journey would have been good enough to passively burn off soot on the long run the day before.

 

If not, then why wouldn’t it have done a forced regen then as opposed to me nipping 10 minutes down the road to the shop when I haven’t even exceeded 40mph?

 

No warning lights to speak of.

Driving over 40mph for a given distance wont clear the dpf unless it has hit a threshold where it needs cleaned. At this stage the car will alter fuel/injection etc to increase the temp at the dpf. This combined with driving at say 50mph in 5th gear for 20 mins should be the best combination to give the highest exhaust temp to best clean the dpf. Once the soot drops to a certain level the car will return to normal and exhaust temps will drop. 

Just driving at 50mph in 5th on a normal run with no additional fuel etc will prob only get the exhaust to 200 degrees C. When the regen kicks in i hav seen mine reach 600.

 

My advice, if u dont hav the adapter and app would be as soon as you see the idle increase to 950/1,000rpm go for a constant drive of at least 6 miles where u can hit 50mph in 5th (roughly) without being brought ti a standstill. Strangely it's exactly how i would describe trying to drive to get greatest fuel efficiency.

 

There are myths that driving at high revs or accelerating hard uphill etc will clear it.  In my experience this may drop if a few % so that the light goes out, but 5 miles down the road it'll be back.