Given the 8 speed gears on the later 4.4s to my mind, the revs don’t get that high even on a motorway run to get the cat hot enough for a regen. Am I correct or does the Rangey have a different system to more normal cars when it comes to to regeneration?

You need at least a half tank of diesel for the DPF cycle to kick in, and maintain a steady 55 to 70mph on the motorway for the car to even think about doing a regen ( that is providing everything is working as it should be - no air leaks on hoses etc etc )

I use a GAP IID and my iPhone to see how it is working, takes about 15 to 20 mins to get it back down to low 3's or 4's

The EGT ( Exhaust Gas Temp ) Bank 1 using Sensor 2 is vital, in normal driving it can read anything from 150 to 250 deg, but when the regen kicks in it shoots up to 600 degrees +

Click image to enlarge

Useful - thanks. Exactly what am I looking at on the GAP tool ? presumably under Live Data or whatever it's called ?

Low 3 or 4's - is that gm's of soot ?

It is not the rev level that initiates a regen but the soot level. you get a yellow restricted power warning at c.19 and a red when it gets to around 27 (may need confirmation).

Speed is also irrelevant. I've had it go at 30 mph but it is advised to do a minimum of 50mph in order to negate the chances of a fire at the high temps.

To initiate a regen it pumps fuel into the exhaust to raise the temp to c.600.

Look under live values. You can tick up to 6 (or 8?) values to monitor on the same page. go for temps and soot level definitely.

Thanks Dolphin - so effectively, just drive around as normal and if it decides it needs to regen it'll do it if it can and if it can't it'll let me know ?

Another uneducated question - does it regen frequently if conditions allow, or only when getting full ?

yup. drive normally so if you start getting RP (restricted power) warnings, then you have an air leak in a pipe or inlet manifold.

I live on the Wirral Jonny, My amber DPF warning came on in Liverpool city centre the other day. Drove through the Wallasey tunnel and down the M53. By the time I got to Clatterbridge the light had gone out. I normally stick between 60-70mph.

It's done it about 3/4 times in the 3 years I've owned the car and I normally take it down the motorway from Prenton and it always goes out around Vauxhalls/Ellesmere Port.

I just turn around and come back then.

The car gets mostly local short journeys with the occasional long trips towing our caravan which is why I guess its coming on!

You don't need high revs for a DPF regen on these vehicles. Post CAT EGT's will be 600+ degrees at a steady 60mph in 8th gear. High revs are not required.

The exhaust gas temperatures are raised by the additional fuel being injected on the exhaust stroke, that fuel makes it's way to the CAT (which is located before the DPF) and an exothermic reaction takes place where that extra fuel is effectively burned. These high temps facilitate the DPF regeneration.

I know that some static (i.e. stationary in a workshop) regens on other makes, call for the revs to be held reasonably high, BMW's for example. I'm not personally a fan of regens being carried out on a non-moving vehicle due to lack of cooling air over components during the process.

Jon 1992 RR Classic 3.9 efi Vogue
2014 Disco 4 HSE
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High revs are not needed, and i think potentially could discourage the regen process. You need the engine to be in a situation where:

- its under light(ish) load so that fuel is being delivered to the engine (as opposed to idle, or over-run downhill)
- there is spare overhead to deliver more fuel than is actually needed for that light load

If you're high-revving the engine, you may be taking away the spare overhead to add more fuel. This is why driving normally above 40mph is best for the regen ... its where you typically drive along with a light throttle. V8 or else ...

I do quite a bit of green laning in mine low revs in low box and I’ve never had a problem with it doing a regen. Never had an amber or red warning. Did a 3 day coast to coast last week with no issues with DPF at all. Just drive it and enjoy it.