It's automatic Neil. Others on here say they know when its going on but I personally can't tell, except occasionally a smell like burning rubber when I get out of the car. Nothing for you to do unless you get a "Restricted Performance" message telling you the dpf is full. Your handbook tells you what to do (just involves going for a drive round for 20 minutes 😀 ).

Sent from my Nexus 10 and a rather nice black XF-S Portfolio

 

The DPF is a can in the exhaust system that collects soot. When the volume of soot starts to restrict the exhaust flow, the car performs a 'regeneration' by burning the soot.

The regeneration process is initiated by injecting fuel on the exhaust stroke which raises the exhaust gas temperature. The process is entirely automatic & you don't have to do anything. The extra fuel used during the regen cycle is very noticeable if you use the 'auto' fuel consumption on the trip. After the car is shut down you'll probably notice a lot more 'pinging' from the exhaust than normal as well as the smell of burning rubber. Nothing to worry about, it's normal!

If the car is used mainly for short trips, the exhaust temperature won't get high enough to initiate the regeneration. The filter will continue to become blocked & a message will appear on the dash. If this happens a forced regeneration is necessary. This involves driving at a constant speed of 50 -70mph for about 20-30 miles with the engine at normal operating temperature.

 

Aw Nick, you should have been a teacher! Put my pitiful explanation to shame . . .

 

I do like to do one informative sensible post a month!

 

Neil, one way to check this is working is to check your exhaust outlets. If you look right up the pipe, the inner wall should be nice and shiny where it has burnt off the soot particles. If not, then you'll probably be due a re-gen shortly. Trip to Moira or Dungannon will see you fine!

 

do you find that it will do a regen at normal revs (ie that it gets hot enough at circa 1500rpm) or do you need to either go a bit faster to raise the revs or put it into sport mode and hold it down the gears o keep the revs up?

Ours was showing poor fuel consumption so I ran it 15 miles up the motorway (return trip so already right up to temp) in sport mode and held it in a low gear to keep it around 3-3.5k rpm. I did notice a bit of surging during the run and it did the fuel consumption a world of good.

 

Once the process has started, 50mph is fine for a complete regeneration. There may be a case for running the engine at higher revs if you're trying to get the gas/DPF temperature up to initiate regeneration.

 

DPF regen is all about exhaust gas temperatures.

These are, in a diesel engine, directly related to how hard it is working. So basically, the harder you work the engine, the better for DPF regeneration.

Empirically, the engineer in me would suggest that you are better off with more accelerator pedal at lower revs than less of the same at higher revs, if your purpose is to raise exhaust gas temperatures. Diesels have no "throttle valve" in the air inlet path like petrols, so if you rev them higher with a light pedal, more air is pumped through the engine, and exhaust gas temperature would drop.

JMHO.

 

DPF regen is all about exhaust gas temperatures.

These are, in a diesel engine, directly related to how hard it is working. So basically, the harder you work the engine, the better for DPF regeneration.

Empirically, the engineer in me would suggest that you are better off with more accelerator pedal at lower revs than less of the same at higher revs, if your purpose is to raise exhaust gas temperatures. Diesels have no "throttle valve" in the air inlet path like petrols, so if you rev them higher with a light pedal, more air is pumped through the engine, and exhaust gas temperature would drop.

JMHO.

Spot on. This is exactly what we found on the alfaowner forum when monitoring exhaust gas temps with some rather in-depth software.

 

When I had my 2.7 I used to go 7 miles up a nearby 'A' road to a roundabout and back again at 50mph (the limit) and the "DPF FULL" warning always went out half way back. I don't think higher speed is relevant, in the handbook it said drive in excess of 40mph.

 

Thanks for that explanation Wilf, I hadn't looked at it like that.

and thanks too to geoffw thats helpful to know.

 

Wilf most diesels this last 5 years or so do now have a throttle valve in the intake or in some cases throttle flaps in the manifold to control egr flow and restrict air flow from the main air intake.

They have got to be a popular item to change nowadays getting gummed up as you can imagine with all the crap from the egr going thru them, O the joys of the modern diesel they are just at the point of god help any one that owns one.

 

Are these air valves not just to change the inlet manifold length or pathway according to revs, or to introduce swirl into the airflow for better lean burn? AKA "Swirl flaps"? Diesels have always worked with wide open inlet tracts, that is why they are more efficient than petrols - lower pumping losses and very lean A/F ratios?

 

No Wilf diesels now have in most cases elec controlled throttle valves they limit just the right amount of air when the egr opens ie more egr less fresh air into the engine. Vw have one that is a very common failure on most 2.0 tdi and they have been around from 2004 so they have been about for ten years don't time fly.

Even the old 2.5 transit had a throttle flap beside the egr but it was a manual operation from the throttle linkage to the fuel pump and thats going back a good few years.

 

Excellent, every day is a school day.

But - the total amount of air going through the engine, i.e. fresh plus egr, must be the same - enough to fully fill the cylinders on each intake stroke - i.e. there is no "inlet manifold vacuum" as you get in a petrol?

 

I've been looking at my manual and it states that the DPF regeneration cycle occurs automatically every 190-560 miles. It takes 10-20 minutes if the car is driven at stable speeds of 40-70 mph. It can take longer if you drive at an average speed of 30 mph.

 

Thanks 4 the replies guys ...It all makes sense now .... I try 2 avoid short journeys so hopefully this won't be a problem 4 me .... Rigger. . I'm off 2 Cong next month. .. that's a nice wee 209 mile drive ... I'll give Moira & Dungannon a toot on the way past .....

 

That's some drive there Neil. You going past Sligo, or cutting through Cavan? Me and missus looking to get some holiday time in the republic in years to come.

 

Via sligo Rigger .... A wee 2 night break between Xmas & the new year ...

 

Neil,

now you've got your car,

wheres the pics?

:nopics:

 

I'm working on that Rigger ... can't post pics from my tablet so will have 2 get Tapatalk 4 my phone ... If I use Tapatalk do I also need photobucket ...????

 

Neil you can upload direct from your tablet asumming of course you have the photos on your tablet.

 

Not sure to be honest, I don't use tapatalk personally.

 

You can post pics straight to tapatalk.

 

Downloading it now ...

 

This is going well .... can't remember my log in details 4 Tapatalk. .. any ideas how I can get them ...

 

Really ... I'm using a Samsung galaxy 4 jobbie .... what icon do I press 2 upload a pic .....

 

Hard to describe but the third icon from the right , if you zoom in it has a picture of a tree in a frame...

 

On the iPad it's this one

 

Ooh I don't get that on this ipad. Is that tapatalk though?