Hi
I've just bought a new VW Passat with the 170 PDI diesel engine. Great car to drive, will let you know in due course if it has any of the trade-mark VW reliability problems!
My understanding of the DPF is that if my driving style doesn't suit the DPF then it starts to block up. The response of the engine management system is to increase the fuel mix being burnt to increase exhaust temperatures. If this doesn't work my engine warning light comes on and I need a new filter! Ouch!
Is there any way to find out how happy my DPF is with my regular commute to work? It includes two 8 mile runs on a motoway at speed - but in 6th gear the engine is only doing 2000 rpm? I'd prefer to modify my driving style (cruising in 3rd!??) before the warning light comes on! (I'm not sure if a sudden drop in MPG indicates this burn-off process occurring?) Does the engine measure the pressure across the DPF?
Thanks for your help.
Edited by Dynamic Dave on 30/12/2007 at 00:02
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Ricden
I would have thought that your usage would be OK. It's mainly the town-bound and slow-grind commute cars that seem to need a new DPF every 5000 miles.
Have you ever had the DPF warning light on?
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The car has only done 1600 miles, but so far no warning light.
I wasn't sure if it's too late by the time the light comes on?
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As I understand it; on these constant regenerative DPFs, you first get a DPF light to tell you the filter is getting over-loaded and to "aid" it's regen by giving it some welly.
That doesn't always work and then you get both that light and the engine management light on [with a loss of power] and it's dealer time.
If it's gone too far there is a risk that a forced regen will destroy the car, so a new one has to be fitted. [At your cost.]
At the moment; my only feedback on these is on a service engineer's fleet Seat and the scenario is: light on and off for a bit and then a dealer visit for a £700 bill - every 5000 miles or so. The dealer has never managed to do a regen; it's always needed a new DPF.
These non-catalysed DPFs seem to be even more trouble than the PSA FAPs - and they were bad enough.
What do you get to the gallon? They seem to use a huge amount of fuel trying to regenerate - so much for global warming.....
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I have a DPF on the Mazda 6.... thoughts...
1. It says the DPF warning light comes on if it has trouble "regenerating" and to therefore (my words) give it some welly. Failure to do the latter over time = dealer visit. And I will add to the last bit = cost.
2. Mixed driving with lots of town in over £3000 miles all fine.... but mpg not great overall. On a long fast run it is great but like the Mondeo TDCi Euro IV before it's not brilliant. but a petrol will have cost more overall in tax/fuel.
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Thanks for the comments.
I didn't realise the DPF had its own warning light. I thought it was the general warning light and you had to guess whether it meant you drive slowly to a nearby garage or go out on a motorway and thrash it!!
So far economy has been quite good - 47 mpg on a regular 13 mile drive to work (10 miles motorway and 3 miles plodding through town). However, good fuel economy requires driving with engine speed in 1100 to 1500 rpm range (except on the motorway when I get to 2000 rpm.)
I've checked the hand book and it says drive at 1800 to 2500 rpm if DPF warning light comes on. My worry is that my quest to break the 50 mpg barrier will clog the DPF!
By the way, I do still rev it a bit as per HJ's running-in guidelines!
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I don't like the idea of cars telling you how to drive them. The driver should be in charge.
It seems that machines are taking over the world.
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Thankfully my Ibiza hasn't got a DPF (just smokes a LOT) but there is a bit in the manual that talks about them, so presumably it'll be similar for a VW. It echoes what Screwloose says, that the DPF light comes on to warn you that its getting clogged so you need to give it an italian tune up to clear it otherwise engine management comes on aswell and its time to go to the dealer.
My Dads just bought a BMW 318d with DPF and I've told him to give it some beans now and again when its warm to clear everything out. We'll see if it works!
Currently driving: 2007 SEAT Ibiza TDi
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Hang on, let me get this straight. Companies are now producing cars such that if you use them gently in order to use the minimum fuel, they go wrong? The lunatics have taken over the asylum (with apologies to any lunatics reading this forum :-))
Edited by nick on 30/12/2007 at 13:28
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You speak for me there nick.
What the future holds when the latest bright spark starts the next trend i can easily wait to see.
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True indeed. There have been mutterings about Cat IV VAG diesels being unsuitable for use on the Channel Islands and to a lesser extent in other "confined" areas.
In at least one case, the car was quietly taken back by VAG.
I'll take good care of my Cat III.
659.
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Absolutely right. Another case of new technology that worked fine in the laboratory - but in the real world.....
What seems to be happening on a lot of this type, is that the DPF hovers around the "regen" point, never really getting a good enough run to reduce it's loading significantly, just using huge amounts of fuel in the process of trying. [This is good for the environment how?]
In the driving conditions of much of England they are untenable - just a very nice little extra earner for the manufacturer.
It's not just VAG that are having to buy them all back - Vauxhall actually fitted them to the "school-bus" Zafiras! [What planet are these people on?]
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>>the DPF light comes on to warn you that its getting clogged so you need to give it an italian tune up to clear it otherwise engine management comes on aswell and its time to go to the dealer<<
'Honestly, officer, it's not my fault. The car told me to speed up in that 30 zone......'
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I had an Audi A6 Hire car in Italy, this light kept coming on whenever I was stuck in Traffic, but once I'd been on the motorway a few Kilometres it extinguished itself, I didn't mention it to the Hire car people in case they made me pay for a new particle filter. . .
So what exactly does it achieve ?
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I think your commute would probably be okay for the DPF. Problems only occur on 'extreme' and prolonged city driving. I have an Audi with the same engine, and noticed that Audi have produced a little leaflet for customers just discussing this very subject and what to do if the light comes on etc. Maybe VW have got the same leaflet. I think as long as you give the car a bit of welly as soon as the light comes on you should always be okay.
I think the ECU does periodic 'regen' cycles, where the fuelling is altered to produce a high EGT to 'burn off' the DPF. I think this is why occasionally my fuel consumption is terrible for no apparent reason.
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How come some EU4 diesels need a DPF and some not? HJ CBCB of my Ibiza says that its EU4 compliant but I'm 99.9% sure its not got a filter.
Currently driving: 2007 SEAT Ibiza TDi
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Emission regulations - common sense.
Oxymoron....
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From a light-hearted point of view I can use the DPF as an excuse at home to avoid any short journeys - e.g. shopping, picking up the kids from friends, taking them swimming etc.
However, from reading the discussions on this forum, they seem to conclude that state of the art diesels are pretty marginal for lots of reasons. AVOID THE FOLLOWING,
1) mis-fuelling with petrol (damages fuel pump)
2) supermarket diesel (inadequate lubrication) (damages fuel pump)
3) wrong oil (this car doesn't use the normal "special" oil for VW PDI engines, but a "special, special" oil for PDIs with DPFs!!)
4) short journeys (engine wear++ and DPF)
5) low speed journeys (DPF)
6) clumsy gear changes (or is it thrashing the car in low gear) (damages DMF)
7) owning a diesel more than 3 years old (no warranty to cover enormous bills when something goes wrong)
8) turning off the air con (not just a diesel problem!)
At least it's not an F1 car! On Top Gear a couple of weeks ago they were saying the F1 engine is so "tight" they have to preheat the engine oil before it will turn over!
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I've now covered 20,000 miles in mine since October last year, I do 120 miles a day on my commute to work and then another 30-50 during the day, this week I decide to see how many miles I could get out of a full tank of fuel.
Everything went well with an average of 44.3 MPG and covering 574 miles before the fuel light came on, well, I thought it was the fuel light, the DPF warning message and lamp flashed up, a little splutter but everything seemed ok.
A good friend works for a dealer and said they suffer with this problem and as long as you catch it early and go for a good run everything will be OK, so thats exactly what I did. A good blast through the FULL rev and gear range turned the light off within a 2 mile stretch.
I'm going back to the normal drive into work from now on, sod the MPG what I loose in MPG will be saved in dealer repair bills, plus I get two cups of coffee in before work and I get home 15 mins early!!!
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I saw the "leaflet" in my local Skoda main dealer a few weeks ago. It basically stated cars equipped with DPF's were not suited to mainly urban driving conditions and that failure of the DPF may not be covered under warranty if the car was used a such. It also went on to specifically mention the channel islands.
I imagine all the non DPF Skoda diesel taxi owner/drivers (octavia's and superb's) will be avoiding the new DPF equipped models.
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The problem for diesels is for Euro IV and certainly Euro V a DPF (or an improvement on the current ones) will be needed. They are not to be idled for a long time and stop-start driving is not advisable.
So what happens to taxi prices? Will the good old black cab become a petrol car?
Edited by rtj70 on 16/01/2009 at 23:18
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Until the early 1990's, I had always had a petrol car. Then someone drove into the back of my car and wrote it off. I had a hire car for a couple of weeks, which was similar, but had a catalyst. The fuel economy was so poor, I was persuaded to buy a diesel.
Since then, I've always had diesels. But I can see that next time it comes to change, I will get a petrol car. Legislation has destroyed the two traditional reasons for diesel - economy and reliability.
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Let us wait to see how DPF develops. They are learning/developing.
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If you look in HJ's FAQ (at the top of the page) there is a VERY detailed bulletin from a VW technician about VW's DPF methodology and deployment, which covers the ideal conditions for regeneration, soot loading levels and more.
That will give you the info you need.
For the VW cars, DPF regeneration happens most efficiently at around peak torque rpm (i.e. around 2,000rpm) and above 38mph. A soot loading of 50% will burn off in about 8-10 minutes this way.
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