10 replies to this topic

[GingerTom]

Thought you Mk4 guys who have a DPF fitted may be interested in this from the Times motoring section.
http://www.timesonli...icle6985968.ece

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It’s often stated that today’s cars have more computing power than the entire Apollo mission that first landed men on the moon. That may be so, but I suspect the same is true of my mobile phone, washing machine and any other bit of my micro-processed modern life. What’s less well known about modern cars is the complex chemical laboratory they carry on board. (If you like details and don’t get put off by very mild science, read the next bit. Otherwise, trust me when I say it’s clever, then move on to the following paragraph).

Catalytic converters eliminate other pollutants such as carbon monoxide (CO), oxides of nitrogen (NOx) and hydrocarbons (HC) by first extracting the oxygen from the NOx, leaving harmless nitrogen, then using that oxygen to covert the CO and HC to carbon dioxide which, although a greenhouse gas, isn’t immediately a health hazard, and water, which at least so far, is still harmless. Because the catalytic converter converts the pollutants to harmless gases, it will last for the life of the car provided it’s not damaged in some way.

But diesel engines have a different problem: soot. It’s invisible and has exotic names like PM 10 and PM 2.5, but basically, it’s soot. It can trigger a host of breathing disorders as well as some cancers, so it clearly needs to be cleaned out of diesel vehicle exhausts. Enter the Diesel Particulate Filter, or DPF. It’s already fitted to most diesel cars on sale, and more or less all will need one from 2013 to meet the requirements of the Euro V1 emission standard.

The problem is, while the catalytic converter converts noxious stuff to harmless stuff and should last forever, the DPF is different – it’s a filter and simply traps the soot particles. This means that it eventually gets clogged up – or “loaded”. Replacement filters are very expensive – they’re full of fine meshes that are costly to produce – so the manufacturers have come up with ingenious ways of cleaning the filter while it’s still on board the car. The simplest way is to heat the filter up so that the soot burns – producing “harmless” carbon dioxide. Six hundred degrees celsius does the trick. However, the exhaust gases have to be hot to achieve this, so the computer controlling the engine management does some clever stuff with injection timings and fuel to raise the exhaust temperature when it detects that the filter needs cleaning. But the engine still needs to work reasonably hard to get the high exhaust temperature – typically the car needs to do about 40 mph or more constantly for about 20 minutes.

That’s fine for many drivers, but not for those who spend most journeys crawling along in urban traffic jams. If the engine doesn’t work hard enough for the soot to burn and clean the filter (or “regenerate” it), a dashboard light will warn the driver – but these days we just want to put fuel in one end of a car and drive the other end. Manufacturers have encouraged us to think that cars are virtually maintenance free between services, so we’re not used to doing strange things to keep everything working.

If the “regeneration” starts, but the car slows down or stops before the process is finished, it’s more or less back to square one. If the car does lots more crawling in slow traffic and never gets a blast down a clear road, the soot builds up and up inside the filter. The performance of the car will start to deteriorate as well because the engine finds it harder to push the exhaust gas out. Eventually, it gets to so clogged up that the filter has to be taken off the car and cleaned out using a special bit of kit in a garage. This is known as “forced regeneration” and will generally cost between £150 and £200. Ignore this warning light, and eventually the filter will become so clogged that the car will be very difficult to start. The filter will also be beyond cleaning and must be renewed – at a cost of around £1,000. As the engine wears, more soot is produced and the DPF will need more frequent regeneration if it’s not to be damaged. It’s also important that the correct engine oil is used – otherwise the filter will block very quickly, and again this will be exacerbated if the car drives in heavy traffic for much of its existence. The trick with a car with a DPF is to make sure there are regular journeys along reasonably fast road with fairly light traffic so that the regeneration can be completed as needed. If the car is used in rural areas the driver won’t even know it’s happening. But if it’s being used as an urban commuter car, warning lights and worry will be a regular occurrence.

If all this strikes you as being a bit extreme for a city dweller, you’re right. The car manufacturers generally now recommend that people who want an urban commuter car should buy one with a petrol engine, or, of course, a hybrid or even an electric car. Anything but diesel. Some dealers clearly haven’t yet got the message. But then, hybrid cars are of little benefit to rural drivers and electric cars are clearly impractical outside large towns or cities. Is there a government information site telling us this? Do the new vehicle labels suggest type of use? Are dealers trained to match engines to lifestyle? No, no and no. We’re used to choosing between three or five doors, hatchback, saloon or people carrier and so on and it seems that no-one is trying to tell us we should consider anything different. The sales literature and showroom information are focused on the car’s running costs and environmental performance for typical motorists. This approach can’t last. We need to make sensible choices about engine type based on how and where we’re generally going to use the car, or increasingly we’ll suffer some fairly drastic financial consequences as well as doing nothing for the environment.

That means we need much more specific advice from both dealers and the Government. Nobody is going to be 'typical' for much longer.

[OverWhatHill]

Another reason for an Italian Tune Up - whoopee! :}

[tripletrouble]

I wonder what the expected service life of a DPF is?

[GingerTom]

The DPFs are causing a lot of trouble in the smaller cars which are only doing short town journeys because they never get up to the high engine speeds for long enough to start the burn process. This is then causing them to block up with resulting engine damage. The manufacturer then puts this down to the driver error.

Another piece of Euro legislation that is unreliable and costly.

[tripletrouble]

I should be fine as 90% of my mileage is on the motorways.

[GingerTom]

That's actually a myth because it's high engine speeds not road speeds that burn it off and going along at low revs on the motorway won't always achieve the desired temperatures even if you do the longer distances.

Just keep it in a lower gear for a while now and again to start the burn process. There should be something in the hand book too.

[nick tdci]

Just found out my focus has one of these rip off dpf's on it just now waiting for prices to get the fluids top up.

[GingerTom]

Anyone tried the jlm dpf cleaner? Its on ebay and you add to fuel. Supposed to allow burning off at lower engine temps. Don't want to try it if its untested on ours.

[malford]

MK4 Mondeo dpf is maintenance free unlike the Eolys system used in some cars.


"Coated Diesel Particulate Filter (cDPF): Ford's cDPF system traps carbon deposits as they exit from the combustion system, preventing their release into the atmosphere.

"Under favourable conditions the system then cleans itself with a controlled 'burn-off' process, thus providing a self-contained clean air system without the need for service maintenance.

"This system contains a ceramic filter body of around 4 litres volume mounted behind the exhaust manifold plus a special regeneration support unit on the engine's intake manifold. Together these components enable the filter system to regenerate in any possible drive condition automatically without requesting any input from the driver and without compromising driveability noticeably during regeneration.

The advantages of the system are:

* Additive systems have an additional additive tank that primes the fuel tank with the additive (a metallic catalyst) at every refuelling. On the Ford cDPF the additive is embedded in the filter washcoat, hence no additional complex priming system is required and no refilling of the tank.

* Long life – a ‘normal’ additive DPF tank needs refilling after approx 60k km, whereas the new Ford cDPF has been developed to last at least 200.000km."

[GingerTom]

Thanks mal that's very useful info.

[Stu C]

Fascinating read lads!

Sometimes you guys amaze me!