My driving style and the DPF

[BigBadBob]

Having had my C5 1.6HDI for 17 months now and 2 MOTs, | have been ignoring an intermittent fault whereby I get the 'Depollution System Faulty' warning coupled with an orange warning light. This occurs usually when I have given the car a bit more welly. It can sometimes also be accompanied by the engine feeling as if it is missing or cutting out momentarily. My 'solution' has until now been to drive the car gently . This came to a bit of a head last week on one of the hotter days when one journey where the 'missing' was occurring almost continuously, making me think about it a bit more. I also had a few occurrences whilst in France recently, and coupled with what I recall from last summer, I have concluded that warm weather makes the problem worse.
In my mind, I have been thinking that my DPF needs changing/cleaning/drilling, and began researching online - which led me to comments like "you must drive it like an Italian". This does not sit terribly comfortably as I bought the car for its economy. Had I wanted to drive like an Italian, I would have bought an Alfa.
So - before shelling out my hard earned readies on the DPF, I thought I would try my best in adopting the Italian style - which is where I need some help. My question is - Should I be driving at the same speed but holding lower gears and using more revs, or do I need to drive the car a bit faster to increase the exhaust gas temperature? I'm struggling to believe that achieving government emissions targets necessitates me driving faster, so for the last 5 days, I have been using more revs but basically the same speed and acceleration (i.e. lower gears). To my surprise, in the few days that I have been doing this, the problem seems to have gone away, and my fuel consumption has not worsened and appears slightly better. It's not been long enough to draw any firm conclusiuons, but can it really be true, that holder a lower gear with more revs, whilst basically doing the same speed, is enough to burn of the soot in the dpf and also make the engine more economical?
I should add that my driving is mainly mixed A and B roads with a little bit of town driving. Until now I had always thought my journeys were fast enough that I didnt need to worry about this issue, but this experience is now making me question that .
Does anybody have any of their own guidelines with respect to how many revs to use? I am now ensuring I don't let the revs drop beneath 1500rpm and trying to ensure a fair amount of time is spent between 2000 and 3000 revs. Have the manufacturers given any clear guidance?

[Northern_Mike]

My question is - Should I be driving at the same speed but holding lower gears and using more revs, or do I need to drive the car a bit faster to increase the exhaust gas temperature?

Sort of, there's active and passive regeneration of the DPF when it gets to around 40% full if memory serves. If you're driving fast enough, I believe that it will automatically regenerate by simply burning the particulates off and it leaves an ash at the bottom of the DPF. If you don't get it hot enough, it'll eventually regenerate actively, where it injects extra fuel into the exhaust gases to get them hot enough to burn the stuff in the DPF. It probably lights the warning light to tell you the filter's partially blocked before it does this, I'm not 100% sure.

[Northern_Mike]

AA, for once, explains it well

http://www.theaa.com/motoring_advice/fu ... lters.html" onclick="window.open(this.href);return false;

[KP]

Get the engine coolant upto temp and then start pushing it hard in the gears. good in a hilly area to do this Boost and heat are what you need!
Then when you've given it 5-10mins of this you need to sit it on a dual carriageway or motorway where you can sit comfortable for about 20-30mins at a set speed above 56mph and it will then run the DPF cycle.


If this fails to often the car gives up trying anymore and just reports it as a fault. At this point you need someone with a lexia to force a DPF regen.

Also make sure you're not letting services pass you by and if possible service it more often than the service guide says. the 1.6 doesn't like extended oil changes as they end up causing issues with the turbo. search 1.6hdi turbo on your favourite search engine and you'll find a raft of complaints about it...

Manufactures expect every now and again a car will be thrashed and a diesel needs this every now and again to clear its guts out. I bought a HDi90 Xantia estate years ago that had 225k on the clock. It had been driven gently for years and was down on power when i got it. within a few miles it was starting to perk up and the exhaust was being cleared out judging from the clouds i could see behind me after that and running it on BioD it was happy forever more and never smoked again

[BigBadBob]

Then when you've given it 5-10mins of this you need to sit it on a dual carriageway or motorway where you can sit comfortable for about 20-30mins at a set speed above 56mph and it will then run the DPF cycle.

Hmm... 3 weeks ago, the car did two 350 mile journeys on motorways and dual carriageways in France doing typically 65 to 70 mph. So I would have thought if the car was going to carry out a DPF regen cycle, it would have done it then.
My thinking was more to do with day to day driving, when I'm wondering if I am either using too low revs or if I need to drive the car faster?

[NewcastleFalcon]

from the AA article linked by Northern Mike

If you continue to ignore warnings and soot loading keeps increasing then the car won’t run properly and the most likely outcome will be that you will have to get a new DPF costing at least £1000

Well thank goodness for a developing aftermarket, the AA's view of the costs of a new DPF are a bit pessimistic

regards Neil

[RichardW]

Those trips should have been enough to regen the DPF if it was going to. Bear in mind though that 'depolloution system faulty' is just PSA speak for "Engine management problem" so it could be anything (got to love the French!). I would think in your case, it's more likely that there's a fuel supply problem, but you need to get it on Lexia to find out what codes are stored. When was the fuel filter last changed - this engine is prone to giving fuel flow problems if the filter is a bit dirty.

The biggest problem with running with a blocked DPF, especially on the DV6 engine, is knackering the turbo due to high back pressure, which adds a good bit to the cost of recification....

[miked]

'Depollution System Faulty' message does not just refer to the DPF. I'm sure I remember reading it could be caused by problems with things like injectors or electro-valves.
You need to get the codes read with a lexia to make certain.

Edit: Sorry RichardW, didn't see your reply.

[KP]

If I recall for the DPF to regen the speed needs to remain constant. If it varies at all in that time period the Regen Cycle is cancelled as it needs to be happy about the exact goings on and that the engine isn't going to become loaded/unloaded when its not expecting it as its injecting fuel post conbustion cycle to get the exhaust temp up and this could damage the turbo and other bits if the engine suddenly started to need to develop full power as the heat thats generated is right on the limit of what the turbo/exhaust can take as im pretty sure during this process the turbo will glow red hot due to the extra fuel and heat in the system....

Possibly another reason for their early failure compared to older turbos. The oil filter thing on them is a bit of a false positive. The oil itself is the issue and proper service schedules are the only cure, not 20k service intervals but 10k at the most. Renault learned this with their early DCi engines...