Any - DPF - What is all the fuss about ?

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Mon 18 Feb 2013 14:38
Any - DPF - What is all the fuss about ? - Mr Fox

Can someone outline in simple terms what the problem is with DPF equipped cars. and under what circumstances they are likely to cause problems.

I have a 2009 Passat CC 2.0 TDI, just done 60 K and now out of warranty and I've never had any bother at all.

it does say somewhere deep in the owners manual that its not suitable for use in places like the channel islands. The implication being that it will only be driven at speeds uo to 40 mph and mainly short runs from cold.

So what are the ideal circumstances for this piece of equipment ?

And is all the scaremongering going on about it now, similar to what we had about removal of lead from petrol in the 1990s, when the nation semed to be more concerned with the state of its valve seats than with its children's brains. as the main benefit of the DPF is to prevent nastly soot particles geting into people's lungs.

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Mon 18 Feb 2013 15:10
Any - DPF - What is all the fuss about ? - unthrottled

As you have ascertained, the 'problem' with DPF is greatly exagerated.

The DPF is essentially a trap that collects soot emitted from the engine. Periodically, the trap must be emptied by burning off the accumulated soot. Burning the soot off requires high exhaust gas temperatures. The harder you drive, the higher the exhaust gas temperature.

So high speed motorway driving in a high gear is the ideal operating environment. But the equipment can cope with most commonly encountered driving styles.

A common myth is that driving round in a low gear with high revs is helpful. In fact, It is coiunter productive because it pushes the exhaust emperatures down.

The engine can artificially raise the exhaust gas temperature-but only up to a point. At low power levels, the engine cannot raise the exhaust gas temperature sufficiently to burn off the soot. Unfortunately, this does waste fuel and some of the excess fuel tends to end up being washed down the cylinder bores where it contaminates the engine oil. In extreme cases the contamination is so bad that the engine can start to 'run away' on its own lubricating oil. But this is very rare.

For most people DPF is not something to worry too much about.

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Mon 18 Feb 2013 15:28
Any - DPF - What is all the fuss about ? - craig-pd130

My Mondeo IV had, and current Volvo seems to have, very robust DPF management -- never had a problem or warning light with either. Well over 50% of my driving is my short commute (less than 4 miles) and 'dad's taxi' journeys of under 10 miles, mostly in urban limits.

When the Mondeo did an 'active' regeneration (which would happen on either a mileage-based regime or when the DPF sensors indicated it was needed), it would typically take 10 minutes start to finish.

The Volvo's regenerations take longer -- up to 20 minutes, but are less frequent.

I would be very interested to see how quickly the soot loading in the DPF falls during an active regeneration. From what little manufacturer data I've seen, a soot loading of around 50% is usually the trigger for a regeneration. I'd like to know how many minutes it typically takes for the loading to fall to, say, 25%.

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Mon 18 Feb 2013 16:15
Any - DPF - What is all the fuss about ? - thunderbird

Totally agree with the above. Have 2 cars with DPF's and only do average mileage in both. Had one 5 years and the other 2 1/2 not a problem with either.

BMW does not regen as often as Kia but when it does it sometimes takes an age, probably 3/4 of an hour once on a drive to Whitby. Easy to spot on the move, the engine note changes but idle remains smooth.

Kia does a regen normally every 300 miles but on a long run it will stretch that to 400 miles. The regens take 15 minutes regardless of how you drive, you can set your watch by it. Regens are more difficult to spot than in the BMW, idle is uneven but on the move the only pointer is the instant fuel consumption read out, it plummets.

One common feature, if you stop during or shortly after a regen the car will smell like its on fire. Don't touch the tailpipe, it gets extremely hot, don't ask me how I found out.

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Mon 18 Feb 2013 16:18
Any - DPF - What is all the fuss about ? - Mr Fox

My Mondeo IV had, and current Volvo seems to have, very robust DPF management -- never had a problem or warning light with either. Well over 50% of my driving is my short commute (less than 4 miles) and 'dad's taxi' journeys of under 10 miles, mostly in urban limits.

When the Mondeo did an 'active' regeneration (which would happen on either a mileage-based regime or when the DPF sensors indicated it was needed), it would typically take 10 minutes start to finish.

The Volvo's regenerations take longer -- up to 20 minutes, but are less frequent.

I would be very interested to see how quickly the soot loading in the DPF falls during an active regeneration. From what little manufacturer data I've seen, a soot loading of around 50% is usually the trigger for a regeneration. I'd like to know how many minutes it typically takes for the loading to fall to, say, 25%.

Thats interesting as we also have a Mondeo IV 2.0 TDCI, and that mainly gets used for commuting to and from work by SWBO with only occasional longer trips, never had any bother with that either. I guess the thing is not to worry about it. so how do you know when the Mondeo is regenerating ? does it tell you via a message on the dash ?

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Mon 18 Feb 2013 16:34
Any - DPF - What is all the fuss about ? - Graham567

" so how do you know when the Mondeo is regenerating ? does it tell you via a message on the dash ?"

I also have the same Mondeo and do ALOT of short trips.The regen process seems very robust in the Mondeo and works well.

When it does one the revs change a bit and the car seems to jag.Abit like when you put a heavy load on ie air con or rear demist.Normally at tick over the instant fuel reads 0.1 gal/hour but during a regen it goes up to 0.2 gal/hour.

I just drive round the streets stopping at junctions to read the consumption.When it drops back down to 0.1 then its safe to turn off.

Never had any bother in the 3 years i've had the vehicle.

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Mon 18 Feb 2013 17:15
Any - DPF - What is all the fuss about ? - craig-pd130

+1 to Videodoctor's post.

The throttle response goes a bit wooly, like older carburetted cars used to run when they were on choke from cold. In fact, the anti-shudder flap in the Mondeo's inlet does close during a regen to choke the inlet airflow, so the principle is similar.

The other sure sign is that the engine cooling fan is always on for the duration of the regen. This can be clearly heard at idle (with the radio off and internal heater fan on low). As soon as the regen stops, the fan switches off. It switches on 1) to increase electrical load on the engine and 2) to help dissipate heat build-up around the DPF canister.

Edited by craig-pd130 on 18/02/2013 at 17:15

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Mon 18 Feb 2013 17:32
Any - DPF - What is all the fuss about ? - spring

How to go from smug to panic in a dozen posts. Have had about 30 cars but just got first diesel so was vaguely aware of DPF. No worries about driving demands on the car - it pops up and down the motorway a couple of times a week. But do I understand that the dials are supposed to be telling me something and if so what. And what should I notice when it's correcting something? And about what proportion of buyers with diesels have ever heard of DPF. (Peugeot 1.6 sw)

Cheers Colin S

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Mon 18 Feb 2013 17:49
Any - DPF - What is all the fuss about ? - madf

And about what proportion of buyers with diesels have ever heard of DPF. (Peugeot 1.6 sw)

Cheers Colin S

All those on whom it goes wrong.

I would say under 1% of owners judgng by the lack of posts. After all, if it was seriously affecting lots of drivers, we would see loads of adverts on people who will fix them etc.

We don't..

Remmebre as motoring journalists grow older, they resist change.

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Mon 18 Feb 2013 18:50
Any - DPF - What is all the fuss about ? - daveyjp
I got rid of my X type when I realised the DPF system was a Ford bodge up job. It would regen every 500 miles and for 20-30 minutes it was a nightmare to drive. After 4,000 miles it would begin requesting an oil change.
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Mon 18 Feb 2013 20:28
Any - DPF - What is all the fuss about ? - craig-pd130

But do I understand that the dials are supposed to be telling me something and if so what. And what should I notice when it's correcting something? And about what proportion of buyers with diesels have ever heard of DPF.

Cheers Colin S

A properly-implemented DPF system should look after itself and not be obtrusive to the average driver. And that's the problem with some early DPF implementations -- they haven't been thought-out and set up right.

I only notice and get interested in the workings of the DPFs in my cars because I'm a complete car geek.

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Mon 18 Feb 2013 20:30
Any - DPF - What is all the fuss about ? - thunderbird

I only notice and get interested in the workings of the DPFs in my cars because I'm a complete car geek.

+1

BMW did regen today.

Kia did one last Friday.

No fuss, they just do it as designed.

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Mon 18 Feb 2013 20:42
Any - DPF - What is all the fuss about ? - Collos25

Two Peugeot 407 1.6hdi sw one did 160km the other 110km the only problem was a loose eloy tank filler cap repaired under warranty.

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Tue 19 Feb 2013 14:34
Any - DPF - What is all the fuss about ? - Mr Fox

No need to panic then, so if I am not mistaken, all cars with DPF will do this "regen" to clear the filter as and when it decides it is required. it is NOT the case than that you need to do only motorway driving to clear the DPF, because the system will decide on its own when to do it, and this could be on the Motorway or on the way to the shops.

This explains whey I've never noticed it on my cars. I was once in a German Audi A6, which came up with a picture of something like a tank full of dots on the dashboard, the driver told me it was to do with the emissions system.

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Tue 19 Feb 2013 14:42
Any - DPF - What is all the fuss about ? - unthrottled

it is NOT the case than that you need to do only motorway driving to clear the DPF, because the system will decide on its own when to do it, and this could be on the Motorway or on the way to the shops.

No. It is easier for the engine to do a regen on the motorway though. The engine won't usually attempt to start a regen until the coolant gets aove about 60-70C or so, and it will probably be interrupted when idling. For most drivers, it isn't an issue.

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