Can somebody please educate me on 'DPF's or Diesel Particulate Filters?!

They seem to the cause of many problems with diesel cars... even people I know have remarks over them.

I've already sort of concluded diesel would never be my engine of choice living in a small area and always hoping to drive a small car like my Panda, and people think I'm mad..

Why is it there, how does it work, why does it cause so much pain for owners?!

Would be nice to have a view next time someone said 'Cars playing up again, think it's the DPF'

Hi,
The only real problem with DPFs is when the car is driven mainly for short journeys, especially in stop and go traffic. These cause the most particulates and give few chances for the DPF to regenerate. If you mainly drive in town or with journeys less than 10 miles a modern diesel with a DPF may not be a good idea. If you do at least 1 long journey, >20 miles, every few hundred miles there should be no issues with the DPF.

Robert G8RPI.

I could go on for hours on this one but basically they are supposed to collect particulate waste - soot ETC - around town then convert it and blow it out the tailpipe when you go for a run - nice! As the emission regs get tighter & tighter they have to put more & more things on diesels in a vain hope of making them cleaner. The sooner they all go in the skip the better, except obviously for truck & marine use etc. Nasty, dirty, noisy horrible things. Yes, they be good on fuel but, you see, I don't really give a monkeys about fuel consumtion hence a 2.4l Volvo!

Maggers has some valid points.

The diesel engine runs best at fixed load and speed. They are pretty useless at "clean" dynamics. I bet you have all seen on older diesel engines (no DPF) that they always spit soot/crap on start up, acceleration, load changes etc. Same for ships and other diesel powered stuff. e.g. British Rail Diesel Electric trains.

Once a diesel engine is up and running at a fixed load and RPM they can be made to be powerful, fuel efficient and relatively clean.

Take this all together and it becomes evident that use of diesel engines in cars not compatible with constant loads.

To get round this they have to add all sorts of management, filtering, recycling, etc. to *try* and make a dirty engine clean.

Bottom line. Burn a dirty unrefined fuel (diesel) then the engine has to do the refining. Burn a refined fuel (petrol, ethanol, LPG, etc) then engine and associated systems (DPF, EGR, etc.) have less to do.

I've only had the one modern diesel car/engine (Croma 2005 1.9 MultiJet) and whilst having owned and maintained Fiat for over 42 years the modern diesel setup is IMHO far to complex, has many scopes of potential failure (especially out of warranty) it is my opinion that unless you drive a company fleet car (their expense/they replace/they backup) or drive 50K to 100K miles per year then the modern diesel engine for private owners will be a tough decision if not a big gamble.

If you dig/google deep then you will find various articles about the ever increasing and potentially unaffordable cost in developing modern diesel engines to meet current and future emissions regulations.

Fleet owners will not be too bothered as they put miles on their vehicles and change them often (funded by the business). Private owners IMHO have a disproportionate funding situation to warrant driving a modern diesel car.

Having said this there will be some/many private owners who change their cars every 2 or three years and have the funds to do this. However they are/will be in the minority compared to those of us who look to own our vehicles long term (beyond 3 years from new).

To add to the above. The soot put out by the engine is not good for us to breathe in, said to be carcinogenic. The good news for anyone with a pollen filter is that the soot particles are larger than pollen grains, so we are protected.
A bright idea was to add a filter to the exhaust to collect the soot. But the filter would need to be larger than the car and need replacing every three months. Trailer filter anyone?
So a small filter is fitted, that of course fills up very quickly. So once up and running, the filter is 'regenerated', by the injection of diesel fuel, or on some cars a very expensive fluid. This incinerates the soot. The filter gets very hot during this process.
As it can only be regenerated with the engine hot and running at a good speed, this causes problems with vehicles doing short journeys.
I can see in the not too distant future, small delivery vans will go back to petrol engines.

A DPF does not have to 'regenerate' if used properly. If you do lots of long journeys are higher engine speeds then the extra heat from the engine will burn off anything the filter catches, the regen only becomes relevant if the filter starts to clog and isn't given the chance to clean naturally.

As for petrol engines? Well PPFs are beginning to appear, petrol engines are very dirty now and pump out a lot of oil and unburnt fuel so DPFs are coming to the petrol engines.

It seems there will always be a war between petrol and diesel fans when really there is nothing in it

AndyRKett said:

... petrol engines are very dirty now and pump out a lot of oil and unburnt fuel

Click to expand...

I'm puzzled at the above statement.
Oil will contaminate a catalyst. Oil is surely more likely to be burnt in the cylinder, rather than "pumped out".
Unburnt fuel is likely to ignite in a hot catalyst. The purpose of the closed loop system with two oxygen sensors is to continually adjust fuel input. Where does the excess come from then?

e

AndyRKett said:

A DPF does not have to 'regenerate' if used properly. If you do lots of long journeys are higher engine speeds then the extra heat from the engine will burn off anything the filter catches, the regen only becomes relevant if the filter starts to clog and isn't given the chance to clean naturally.

As for petrol engines? Well PPFs are beginning to appear, petrol engines are very dirty now and pump out a lot of oil and unburnt fuel so DPFs are coming to the petrol engines.

It seems there will always be a war between petrol and diesel fans when really there is nothing in it

Click to expand...

Hi,
I think this may be a little generalsed. There are different types of DPF implementation. All need som kind of "fuel to burn off the soot. The mJTD injects extra fuel on the exhaust stroke, some inject fuel directly into the exhaust and some have a special additive that is mixed automatically with the fuel (not AdBlue, that's for NOx reduction). It is the latter type that don't operate on a cycle.

Robert G8RPi.

Has anyone else read the COSHH data sheet for petrol!!!! I personally hate the stuff and it is positively lethal in raw state. The additives are extra ordinarily toxic and the arguments that petrol is better are at least uncertain. There is no answer in the burning of fossil fuel alternatives. If we want to be cleaner, we must use public transport. Personally I will do this only when compelled as it is so unreliable and the cost is outrageous.

...... although some recent journey times are beginning to make me re-think my attitude.

petercresswell said:

Has anyone else read the COSHH data sheet for petrol!!!! I personally hate the stuff and it is positively lethal in raw state. The additives are extra ordinarily toxic and the arguments that petrol is better are at least uncertain. There is no answer in the burning of fossil fuel alternatives. If we want to be cleaner, we must use public transport. Personally I will do this only when compelled as it is so unreliable and the cost is outrageous.

...... although some recent journey times are beginning to make me re-think my attitude.

Click to expand...

I reckon if I had to I'd be fine cycling everywhere! Then using a train to get to the big cities of the UK and onwards to Europe if needed.

Though i hope this doesnt happen in my lifetime, who knows?! Isn't our fossil fuel usage literally always a steeper line on the graph?! :O

At least as Fiat fans our fuel consumption ain't as bad as the gas guzzler fans

SB1500 said:

I reckon if I had to I'd be fine cycling everywhere! Then using a train to get to the big cities of the UK and onwards to Europe if needed.

Click to expand...

Growing up in a very hilly area had me off the bicycle and onto a moped at 16. Had an engine ever since.
The railways were created in regions, so travel to London is easy, cross-country often very complicated. Often a lovely way to travel, but expensive and slow.

SB1500 said:

Though i hope this doesnt happen in my lifetime, who knows?! Isn't our fossil fuel usage literally always a steeper line on the graph?! :O

At least as Fiat fans our fuel consumption ain't as bad as the gas guzzler fans

Click to expand...

Whatever our fuel usage, it will run out sometime. If we try to eke it out, it just prolongs the agony. "Saving" it for future generations will only work if they don't use it either. So it's mine, all mine!:devil:

With your 109K and my 97K I reckon we have used quite a bit already... I was totting up the other day and have exceeded 1.5 million miles - and in some pretty awful comany cars as well so I think its time I stopped...... However I agree with Portland Bill. That really made me laugh.