How does DPF regeneration occur?

[MikeT]

I know the basic principles but would like to read the official description if available. (ie a Citroen info rapid or bulletin perhaps?)

In particular, the post-injection of fuel and cross-contamination of other fluids and it's potential "side-effects".

If anyone has a link or can copy n paste here I'd be most grateful. It could (should) also be made a sticky imo.

[myglaren]

This any use to you?

[MikeT]

This any use to you?

Thanks Steve, reading it now...

[MikeT]

This any use to you?

It was informative - especially the part that admits oil contamination of the filter. But ideally, I'd like a step-by-step process of the whole procedure, such as when and where actions occur as I feel there's more concerning side-effects to be aware of.

Having said that, it did confirm a claim that the air coming out of the exhaust is often cleaner than the air going into the intake! Everyone should get a diesel with DPF and we can avert climate change in one fell swoop

[MikeT]

Seems there's more reason for early oil changes to these engines (HDI with DPF). The post-injection(s) of fuel will further contaminate the oil. (Might explain why my first experience of an oil change was "ewwww, that's super stinky!)

Also discovered the EGR valve is closed during regenerations which although understandable is also a bit of a shame as I'm sure it would benefit from a bit of soot-burning every so often. Ditto for the turbo vanes perhaps?

[andybsmith]

I just go for a motorway drive every now and again, low gear high revs 3000 ish for about 10 miles seems to keep everything nice and clean

[MikeT]

I've had the car a while now and occasionally check the regeneration data on lexia.

My style of driving rarely sees high rpm's, certainly not sustained yet the regens are occuring (without any noticeable effects) and presumably complete successfully without problems. I feel the advice to keep revs high may be well-intended, and to some degree desirable, but obviously not necessary for regeneration to occur.

[dnsey]

It's an advantage (perhaps the only one!) Of the Eolys system - lower temperatures are needed for regen than for most other systems, which might well need high revs to achieve them.

[MikeT]

Does anyone know what triggers an active regeneration? I'm assuming it hangs on the estimated "soot load" as many online advises state it to be around 45%, though I've seen mine reporting as high as 55% without regen.

[MikeT]

I recorded live DPF parameters last night as I was hoping to catch an auto-regen in progress during a pleasant evening's drive last night as I'm trying to observe the "tells" of a regen in progress.

What I found during appx 1hr's drive, was the exhaust temperature appeared to be highest at lower rpm's and cooled down at higher WOT rpm's (ie, accelerating hard to national limit).

ie.

Note Soot Load is up to 66% so it possible a regen was in progress.

[RichardW]

Mike

On my 307 there is some clicking evident from the BSI during a re-gen, and it runs slightly rough on trailing throttle. Never noticed anything like this on the C4. In damp conditions you can tell as the HRW comes on. I have heard of people wiring an LED across the drivers mirror heater which will light up when it's on - if this happens when you haven't got the HRW on, then regen is in progress.

[MikeT]

I haven't noticed my BSI clicking though I mostly have the radio on (or passengers continuously talking), Richard.

I think the exhaust temp is the best tell, though i've yet to confirm the regen was in progress when I recorded the above. I'll compare the temperatures after the regen has shown to have completed, which at 66% soot load, should be imminent.

I was hoping the trademark 2krpm hesitation would prove to be a result of auto-regens (it troubles me a lot) but since carrying out a forced regen, it's not been as big a pain as it can be. Coincidence? Too early to tell but fingers crossed.

Another thing I noticed from the parameters was the air manifold temperature was largely 10degrees or so less than the flowmeter air temperature - until the end of the drive, as shown. Assuming the former is at the mixer (where it controls the mix of intake, egr and intercooler airflows) and the latter at the MAF, the values didn't quite make sense to me during non-regen operation.

[bobins]

I've noticed the aircon in my C5 X7 stopped blowing air conditioned air one night whilst driving up the motorway. It only happened for a short while, and the tell tale was the inside of the windows starting to mist up. No amount of prodding the demister button would get it to demist........ then - as if by magic - it started to clear. I put it down to the aircon being deactivated by a regen. No idea if that's what's supposed to happen, but it seemed like a reasonable answer at the time.

[MikeT]

Sorry to be contrary bobins but I just went for a drive with my A/C on min while recording a regeneration in progress. It had no affect I could determine, cool air continued to circulate around me in this sweltering heat.

For those interested, this is an edited video of said recording showing increased average distance travelled between last 5 regenerations which is the effect of carrying out a forced regen a little while back. Prior to this, the average was around 311km.

[bobins]

Fair enough ! I wonder what made my aircon decide to stop working for a short while ? Although the way the earlier and more recent C5s operate whilst doing a regen might differ ?????