Why does.......

[Plym Ian]

My car nearly always seem to start a regen literally 2 mins from home when all i want to do is get in.

Just been on a 50 mile round trip through fast twisty country lanes and then it decides no im going to do a regen when its least convenient for you. Damn you Vauxhall damn you

[Butt0ns]

Been there. I stop at a station regularly on my way home after doing 200-300kms, twice a regen has been in progress when I've pulled in. Only this week on a 8 minute motorway journey I stopped at the lights at the end of the motorway and a regen was in progress. It finished (or cancelled) by the time I pulled up 3 mins later.

[2000rpm]

Manufacturers lead us to believe that regens occur during fast driving when exhaust gases are hot but I strongly suspect that DPFs don't passively regenerate much, if at all, under any driving conditions. I think DPFs only clear their soot when an active regen occurs.

In fact, I suspect that not only short journeys, but faster driving, keen driving, or towing adds a lot of soot to the DPF and increases the chances that a regen will occur. When I had a diesel, it seemed most likely to regen at the end of a long fast journey which often meant either interrupting a regen or taking a 20-minute detour.

So my suspicion is that the least number of DPF regens is likely to occur in cars that spend most of their time cruising at 35-50mph since that speed range tends to be the most economical.

[Dustyone]

Worse time for a regen to start is when you are two mins from home with the weekly shop in a summer heatwave, frozen foods in scrap bin instead of freezer.

[Minuteman]

Never had a regen (that I knew off) in the old 2.0 Cdti but then none of my driving was chugging around town

[ilunn]

what actually is the regen doing.

[Plym Ian]

what actually is the regen doing.

Causing nothing but misery for us diesel owners

[2000rpm]

what actually is the regen doing.

The DPF traps soot from the exhaust gases, hence no cloud of smoke spewing out the exhaust of modern diesels.

When the DPF is close to maximum soot capacity the engine burns extra fuel to heat the DPF and burn off the soot.

If the DPF is unable to finish a regen it will try again next time the engine is started and once fully warmed up (it can take 10-15 minutes for engine to warm up in winter, and another 10-20 minutes for regen to complete).

The more regens get interrupted the greater the risk of warning lights, limp mode, contaminated engine oil or even damage.

[ilunn]

The DPF traps soot from the exhaust gases, hence no cloud of smoke spewing out the exhaust of modern diesels.

When the DPF is close to maximum soot capacity the engine burns extra fuel to heat the DPF and burn off the soot.

If the DPF is unable to finish a regen it will try again next time the engine is started and once fully warmed up (it can take 10-15 minutes for engine to warm up in winter, and another 10-20 minutes for regen to complete).

The more regens get interrupted the greater the risk of warning lights, limp mode, contaminated engine oil or even damage.

But is it not then throwing it all out of exhaust but in one lump anyway?

[markinuckfield]

My car nearly always seem to start a regen literally 2 mins from home when all i want to do is get in.

Just been on a 50 mile round trip through fast twisty country lanes and then it decides no im going to do a regen when its least convenient for you. Damn you Vauxhall damn you

Just had this 5 minutes from home

[markinuckfield]

But is it not then throwing it all out of exhaust but in one lump anyway?

No it superheats the dpf and burns the crap off in very small particles

[ilunn]

Thanks that makes bit more sense now.

[markinuckfield]

Thanks that makes bit more sense now.

It’s a shame that the particles are really bad for humans and go very deep into the lungs, still the eu knows best

[2000rpm]

But is it not then throwing it all out of exhaust but in one lump anyway?

In theory it's capturing soot and then at a later time turning it into mostly CO2.
It's a great way to make diesel CO2 emissions look good because in the 20-minute NEDC test the car will start with a clean DPF and it won't need to regen.
However, if a diesel car had to do the NEDC test every day for a few weeks the CO2 emissions would be much worse as it tried to regen and quite possibly the DPF would be ruined.

[richoxon]

my last car was a diesel but not a vauxhall. never did a regen in 13 years !!!! then i had to buy a new dpf