DPF - when does regeneration finish?

[Legojon]

Bit of a weird one. Ive read loads about DPF and have downloaded an app so as not to be caught out by mine. Was in a rush yesterday so guaranteed the car started a regen. I continued driving till it finished and the exhaust temp dropped to around 260. Then i parked. Later drove home. Washed the car.

I usually get a little build up of soot on the exhaust over a couple of weeks. With a shiny car i drove to my parents. Booting it to overtake a Sunday driver. The car hesitated badly like something was blocked and suddenly cleared. Parked at my parents, loads of black soot around the exhaust (8 miles).

My question is. During regen it burns off the soot and releases it. But after regen finishes am i supposed to drive further? Does turning off just after a regen completed leave the soot in the dpf?

My usual soot load is max 19%. Usually drops to about 5% afterward.

 

[M7R]

Are you artificially forcing it to regen around town etc rather than the optimum conditions of crusing on the motorway etc? As it is not ideal to keep forcing a regen, it is a last resort.

If driven properly with a good mix of country and town motorway you should never need to force a regen, the wife's exeo is a 170 that mainly does town work, 35mpg average! That will happily do a regen around town if it's wants and over the last 40k and 4 years plus so far never had a problem and when the slot loadings were checked on vcds it was looking like 130k+ before the DPF becomes full.

The car will regen as when it wants (it appears that cars that have had the Fix on CR model do like to regen a lot more annoyingly).

Remapped cars are worse as they are generally driven harder and one way of keeping combustion temps down is to over fuel, which naturally means more soot so a quicker filling dpf, and a DPF won't regen unless it's on steady part throttle crusing around 2000 rpm,

One easy way to tell if the car is trying to regen is the gear shift indicator, if it's asking for 3rd at 30 and wants the revs higher then it's trying to do a regen, if it can't do it for 3 or so attempts then it will throw a wobbly, but you can turn it off part way through and it will be Ok so long as you don't keep doing it. You will also use less fuel as forcing a regen means burning more fuel.

 

[Legojon]

I haven't forced a regen yet. I think I do have some kind of DPF issue as its doing a regen about every 175 miles. The last regen was boxing day, I think it started on the last stretch of 50mph dual carriageway and by the time I realised it was doing it, I was stuck in a 30mph one way system. But the previous regen (only 8 days ago) I was celebrating cause I'd literally just got up the motorway sliproad when it started and had 40 miles of clear motorway ahead. I left it in 5th to keep the revs between 2-2.5k and waited for the regen to finish (12 minutes) then put it into 6th and stuck the CC on.

I can't see anything obviously wrong, my current soot loading is 10% (calculated) and 3% (actual). Not sure what the difference is. Ash loading is 0.04l which a google suggests 0.01l per 10k is about right and I'm on 39k.

 

[M7R]

Okay your first post said you had an app, and garanteed a regen, which I took to mean your app can force start a regen.

There's no need to sit on the motorway in 5th at 2500, it will happily do it in 6th at 60 to 70 mph as it can go down to about 1400 rpm if the throttle loading is steady, ie crusing. If you start demanding too much throttle due to too high in the rev range then it will stop regen. As I say just follow the dash gear change, if it wants higher revs for the regen it will tell you to shift down.

175 miles between regen is short though, but could be a few things.. remap and the way it's driven? Fuel (my older vws with no dpf smoked like troopers on Asda fuel... but we're clean on Tesco so I don't use Asda now at all), do you use a fuel additive like Miller ecomax or Rhino? As depending how they change the combustion it may make more particles,

Also have you have the emissions fix on your car?

Any faults logged with VCDS? As not all faults cause an emissions light to come on.

What driving do you do? Mostly town? Short trips? As the wife's exeo will want a regen more often if only she drives it in town on short trips, long motor way trips extend the range as you get passive regen when crusing (temp gets high enough that it slowly regens without having to inject extra fuel, it won't clean the dpf but does help slow the loadings)

 

[Legojon]

The app is just a monitor that does a countdown to next regen. Its been spot on every time so far. At the moment it says I'm 43% to the next regen but its only been about 50 miles since it last did one.

Ah, cheers for the tips. I didn't want to risk 6th gear as I wasn't sure at the time. But also I tend to panic when it regens and end up being more aggressive on the accelerator thinking I'm helping.

Its Revo Stage 1 at the moment and I tend to drive it quite hard. I do use VPower Diesel, but being paranoid also put a fuel additive in (using Archoil at the moment, but was Millers before).

I didn't get the emissions fix as I thought the Revo map would overwrite it anyway. No faults shown in VCDs. I do mostly dual carriageways (40-50mph). But a couple of times a month I get varying motorway trips varying from 80-300 miles.

I've noticed after the regen completes, for a few miles (10-15) if I eg drive at 2000rpm in 2nd and then push the accelerator I get a maybe 1.5 second delay. But eventually its almost like clearing a blockage (sometimes with a squeak sound - from the exhaust I think). But once its cleared, I've tried the same test holding 2000rpm in 2nd and even the slightest touch to the accelerator is an instant response.

 

[M7R]

Hmm sounds like a mix of things then.

If your using V Max fuel then don't bother with the additive as well as it basically gives too much of a good thing and goes past the sweet spot, use normal fuel, normal fuel and an additive or premium fuel, personally I just use normal fuel as the gain is little but others swear different.

Driving hard on a mapped car can make more soot as as yours is a 170 they aren't the most economical to start with which all adds up to faster loadings.

The key thing is don't try and guess what the cars doing, just follow the on board computer and it will do what it wants to do when it wants to do it, no point trying to drive at higher revs as it may stop it doing the regen.

As for the squeak I'm not sure, it could be an after effect of the regen or it could be a genuine problem with the dpf which is also causing more regens.

The best advice I can give is drive more normally rather than flat out and see what happens, if the regens slow down you have the main problem.

Winter doesn't help though as engines work harder for more electric loads, winter fuel isn't as efficient due to the anti waxing agents, plus frictional losses through thicker oil, stiffer bearings etc all add to lower mpg meaning more fuel burnt and more soot.

First I'd try less throttle and what happens to rule out driving style.