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DPF What is it?

richsprint

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Lot of debate around this topic, whether its legal or not.

At the moment the MoT wont detect if the DPF has been removed or not. If I had a diesel and removed the DPF I dont think I would declare it unless I had a performance enhancing remap also.

I guess if an insurance company really wanted to screw you they could find it had been done, and then say you had changed the EU type approval of your car's emissions, and reject your claim.

Diesels days are numbered as the emissions are too dirty, too much cancer causing smoke. The UK is failing its air quality EU targets, so expect to see higher tax on diesel cars and fuel fairly soon. The future is hybrids or small petrol turbos with stop start.
 

Conalflood6

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Cut er out and deprogram her, just leave the box behind but gut the insides, I've had mine done for a few years now, never had a problem, more power also, remap helps 198bhp 2.2IDTEC
 

apintofmild

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Can someone clarify for me: Does regular driving at 'high speed' (presumably getting the DPF nice and hot) clear the accumulated particulates from driving at 'low speed' or can only a regeneration cycle do this?

In other words will the filter just take care of itself under 'ideal' driving conditions with the non-exclamation DPF light only coming on if you're not getting it hot enough for long enough regularly enough?

I've not had any lights at all yet, but I accept it comes with the territory...

 

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Yes Matt, the dpf regeneration cycle is always active in the background and the system is monitor temps and pressures to make decisions on when to invoke a regen.

You should never see the light. If you ever do then it's because the system has been unable to complete a successful regen and needs the driver to take some action.

My Beemer has this week covered nearly 128k miles in 3.5 years. I've genuinely never seen the dpf light.
 

edgeoftime

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richsprint said:
Lot of debate around this topic, whether its legal or not.

At the moment the MoT wont detect if the DPF has been removed or not. If I had a diesel and removed the DPF I dont think I would declare it unless I had a performance enhancing remap also.

I guess if an insurance company really wanted to screw you they could find it had been done, and then say you had changed the EU type approval of your car's emissions, and reject your claim.

Diesels days are numbered as the emissions are too dirty, too much cancer causing smoke. The UK is failing its air quality EU targets, so expect to see higher tax on diesel cars and fuel fairly soon. The future is hybrids or small petrol turbos with stop start.

Just as the calor gas would make motoring cheap? We were advised that diesel was the way to go, now it is a pariah, petrol if exclusive would also be in the same boat, sod the EU, AND THE GREENS. Lets get back to burning coal, and smog in the winter months.
 

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Although I don't drive a diesel, I've had to get up to speed with DPF's because my son has ended up buying an '06 Seat Leon TDI FR

I could be wrong, but I think that there seems to be a bit of a misunderstanding about why DPF issues arise, and what to do as soon as the light comes on.

My son had only had the car for a couple of weeks when he texted me to say the DPF warning light had come on. No surprise since he was doing short journeys. I looked in the owner's manual for his car (he doesn't live here, but I have the owner's manual because he's a berk) and I found this page

Note that this is for a Seat Leon TDI FR



So he did as told (drive at a constant 40 or 50 mph at 1400 rpm for about 10 minutes), and the light went out.

I've been doing a bit of reading, and I've come to the following conclusions:
1. you don't "thrash" or take the car out at "high speed" to get the DPF hot, the ECU heats it up for you by altering the fueling
2. as already said in this thread, the ECU has probably been trying to do this, but you never gave it a constant speed and rpm for long enough for it to do the job
3. if you look in your owner's manual (for any modern diesel car), there should be something similar to the page above
4. if you do a lot of motorway driving, you're not getting the exhaust hot (70 mph only requires about 25 to 30 HP), but you're giving lots of time for the ECU to perform the regen cycle whenever it wants to
 

apintofmild

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freddofrog said:
I've been doing a bit of reading, and I've come to the following conclusions:
1. you don't "thrash" or take the car out at "high speed" to get the DPF hot, the ECU heats it up for you by altering the fueling
2. as already said in this thread, the ECU has probably been trying to do this, but you never gave it a constant speed and rpm for long enough for it to do the job
3. if you look in your owner's manual (for any modern diesel car), there should be something similar to the page above
4. if you do a lot of motorway driving, you're not getting the exhaust hot (70 mph only requires about 25 to 30 HP), but you're giving lots of time for the ECU to perform the regen cycle whenever it wants to
That's what I was getting at, but you've expressed it more eloquently than me! In my post 'high speed' and 'low speed' is the terminology in the i-DTEC owners manual.
 

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When i had rear silencers removed , an unexpected side benefit was that i could hear when the car was doing a regen , it came every 500/600 miles or so and would last around 10/12 mins , during that time you would physically see plumes of smoke gush out after ticking over at traffic lights and pulling away ( obvs the build up being burnt off ) a DPF light can also be triggered by switching off the engine mid cycle i.e.not allowing the car to finish its regen , and WILL go back off again once it has been able to complete it . Yes even the check engine and ! One .
A flashing one is a different matter
 

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The Accord owner's manual doesn't give a specific engine rpm, but there's more info there than in the Seat Leon owner's manual
 

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I've seen loads of those Leon's and other vag cars with the same (BMN code) through our workshop for dpf.

They have an injector wiring loom recall on them so check with Seat to ensure its been done. Over fuelling sometimes kills the dpf but generally on a 9 year old car you want to budget for it anyway.
 

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On a forced regen they get up to 1000 Fahrenheit
 

freddofrog

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edgeoftime said:
Can the exhaust get that hot?
under normal operating conditions ....no

under normal operating conditions, the rough rule is "a third, a third, a third" , which means that of the fuel burned in the cylinder, the heat energy comes out in 3 ways
1. out of the shaft, this goes through the gearbox, diff, driveshafts and into the driven tyres, which pushes the car along the road
2. out of the engine block and sump, radiated directly, and some from the radiator
3. out of the exhaust

A car needs 25 to 30 HP to move through the air (and overcome the tyres' rolling resistance) at 70 mph
If we take 27 HP (20 kW) at the wheels and neglect transmission losses, then the engine is consuming about 60 kW of fuel
1. so 20 kW lost as heat in the driven tyres as they are "twisted" to push the car along at 70 mph
2. 20 kW of heat radiated from the engine etc
3. 20 kW of heat going through the exhaust

But there is a considerable air-stream at 70 mph, so the driven tyres, the engine etc, and the exhaust are all kept cool

Although there is less air-stream at speeds below 70 mph, there is also less heat energy going into the three parts

At speeds higher than 70 mph, the drag is the dominant factor, and power required to overcome drag is proportional to the cube of the speed. So for a car requiring 20 kW at the wheels at 70 mph, there will be 160 kW at the wheels at 140 mph (because 140 = 2 x 70, and 2 cubed = 8).
So for the car requiring 20 kW at 70 mph, it requires 160 kW at 140 mph
1. 160 kW lost as heat at the driven wheels
2. 160 kW lost as heat radiated from the engine etc
3. 160 kW going down the exhaust

The air-stream cannot keep everything so cool, so the exhaust will run a lot hotter at 140 mph than at 70 mph.

So why don't you need to drive at 140 mph to heat up the DPF ?

Because extra diesel is put into the exhaust to heat it up, as in point 1 in #126

edit: and there are at least two ways of doing this
A. firing the injectors again when the piston is at the bottom (start of the exhaust stroke)
B. having an extra injector in the exhaust and squirting diesel into the exhaust

Obviously, if this was ever done on a petrol engine, things would get a bit hairy
 

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Nothing to do with the DPF aspect, but there is a slight brain fart in a part of the above.

I always ***umed that the mechanical power delivered at the wheels went into heating the tyres (rolling resistance) and, as you go faster, into heating the car/air (due to the drag). For some reason I stated in my post above that it all goes into heating the tyres :eek:

In fact once you are over 60 mph, and definitely over 100 mph, the drag dominates, so on the motorway a very large percentage of the mechanical power at the wheels goes into heating the car/air. If you think about an aircraft, the "mechanical" power as thrust (either from a prop or a jet itself) entirely causes the aircraft skin to be heated as it is pushed through the air.

It took me a while to find a decent explanation, but this link describes it nicely
http://www.thenakedscientists.com/HTML/questions/qotw/question/3046/

To summarise the content of the link
i. the air temp outside an aircraft at 10,000 metres is about 223 Kelvin (-50 C). At Mach 1.2 the skin of the aircraft would be heated to about 288 Kelvin (+15 C)
ii. Concorde flew at Mach 2, which heated the skin of Concorde to 373 Kelvin (100 C) causing the aircraft to expand in length by 30 cm
iii. at sea level in an ambient temperature of 17 C, if you travelled on a motorbike at 480 mph, the air around you would feel the same as your body temperature

So when you are traveling at 70 mph and the car is producing about 20 kW of mechanical power at the driven wheels, a fair proportion goes into heating up the skin of the car as it is pushed through the air. When travelling at 140 mph requiring say 160 kW of mechanical power at the driven wheels, most of that goes into heating up the skin of the car. But bear in mind that that heating power is relative to Kelvin, not Celsius.

Finally, back to the DPF itself .....

As said, the DPF is not heated by normal or even severe operation of the engine, but it is artificially heated by arranging for diesel fuel to get into the exhaust manifold, and the engine ECU does this when necessary. One of the strategies is to do this when the back pressure rises, I presume that there must be a pressure sensor for this. If this strategy is being used, IMO a useful feature for the driver would be a simple display of the back pressure (maybe a series of LEDs similar to some ECO lights). This would mean that as the back pressure increases with mileage, the driver will know that a DPF regen is going to take place soon, and this would save a lot of misunderstanding and fear about DPFs in modern diesel cars.
 

apintofmild

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freddofrog said:
As said, the DPF is not heated by normal or even severe operation of the engine, but it is artificially heated by arranging for diesel fuel to get into the exhaust manifold, and the engine ECU does this when necessary. One of the strategies is to do this when the back pressure rises, I presume that there must be a pressure sensor for this. If this strategy is being used, IMO a useful feature for the driver would be a simple display of the back pressure (maybe a series of LEDs similar to some ECO lights). This would mean that as the back pressure increases with mileage, the driver will know that a DPF regen is going to take place soon, and this would save a lot of misunderstanding and fear about DPFs in modern diesel cars.
I had the exact same thought! Whilst it might be of no interest to some (most), I would very much like an extended info page where I can see the back pressure and DPF temperature to see when one is approaching, manage my driving to ensure it completes when active, and generally monitor the DPF health. As mentioned elsewhere, it is a long-term consumable item so a heads up to when it is likely to need replacement would be handy -this might also benefit potential buyers of used diesels (of all marques) so they can factor that into their purchase decision. I can't find anything with my cheepo OBD reader, so I imagine the sensor data is buried deep in HDS land.
 

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I know that this will be shot at by all, but how many detractors on here drive their cars properly, lots of talk about MPG, and fuel efficiency, I bet some of you watch the "pretty" little computer thing moving across the display to see how much diesel is going through. Then read the full info it gives you whilst sitting on the drive allowing the turbo to cool before switching off?? LOL

yes VICTOR is back. LOL
 

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Yes there are pressure differential and exhaust gas temperature sensors in every active regen dpf implementation. Some have multiple sensors to measure temps and pressures at different points in the system to help calculate more accurately the status of the system.

But this is the important point to remember and one that creates confusion with most car owners. The system is always making a guess based on calculations that are being made from sensory information.

If any one of those sensors is not working correctly or optimally then the calculation is more likely to be inaccurate. And in many cases even though the sensors are fine, the cartridge is just becoming blocked but the system believes it's still within operating thresholds.

The upshot of all this is that not seeing a dpf light doesn't always mean you don't have an issue. The system is always guessing.

The best way to tell is from the smell emitted from the exhaust, note of the engine and general performance/economy in my experience.
 

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Been reading this thread with trepidation, can anyone here describe what the effect of the car regenerating whilst on the move feels like, the book says you will note a difference but what difference? Any one??? I know what going into limp mode feels like 7th gen fuel filter etc, but does this passive regen actually improve the performance i.e would you feel it dropping off before the dash board starts flashing, all very confusing, if "they" can warn you of impending trouble why not tell you that all is good, like the check list on the old motors that told you when a bulb was bust.
 

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No difference whatsoever in performance except for a drop in mpg , if you have have ever driven an old motorbike stuck slightly in high revs .... A bit like that
 

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nick said:
Didn't read the whole thing but looks like a very technical explanation. From what I've read on the internet nearly every manufacturer is having problems with their DPF's (well, when I say manufacturers I mean the poor consumer who has to pay for a replacement. What I don't get AFAIK the dpf is there to catch all the horrible particulates from the Diesel engine to stop them getting into the atmosphere, when in reality it just stores them up then burns them all off in one big go. Seems loopy to me.
I agree with you...... but I think the overhfuelling during regeneration combusts the particulates into a gas before releasing them - its the solids (particulates) that get into peoples lungs and starts the cancer mechanism .....however the proposition that you have to drive an additional journey and create even more pollution and burn fuel just to clear the filter is an absolute joke and only one that the EU could dream up. My car has done 52K with no reported incidents (according to the dealers who have looked after it anyway) but the first sign of trouble and off it comes!
 

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pauljdh said:
however the proposition that you have to drive an additional journey and create even more pollution and burn fuel just to clear the filter is an absolute joke and only one that the EU could dream up.
LOL

it's not that simple, and it's also most probably driven by car regs in the USA (I think that California has the tightest regs in the world)

it works like this ....
Over the last few decades, regulations on air pollution get tighter and tighter, and each industry gets many years to prepare for the date of when the new regulations will come into force, and the details of the regulations.that will come into force.
If it wasn't for regulations, every industry in the world would operate in free market conditions, in which the health of all species on the planet are completely disregarded. This is known as an "externality" in industrial economics (in particular, a "social cost")

The research institutes in each industry propose solutions for the companies in the industry to use, and the companies then use the solutions, or variations on the solutions. That will be how the DPF evolved, there would have been other solutions that got abandoned, either because they were too complicated or were taking too long to perfect.

One doesn't have to "drive an extra journey" unless one is using the diesel car every day for very short runs to and from school (for example) ...in which case one has the wrong solution for transport.

Whether the DPF regen is "guesswork" or not (quoting from Fahad #143) is not the point, I still think that if the ECU "believes" that things are getting close to a regen condition, there could be a set of LED's on the driver's dash (like "economy" LED's in some cars) so that the driver will know why the DPF light has come on e.g. the ECU had started a regen but the driver switched the engine off, whereas if the driver had known from a series of LED's, they could have left the engine running until it had finished (I actually do this when the cooling fans come on in my car, I keep the engine running until the fans stop, because the water pump is still circulating the water, which IMO is better than just switching off)
 

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Problem with that is the majority of drivers are not conscientious car enthusiasts like us who would be happy to make some manual intervention when prompted..

The majority of people don't get how cars work and just want them to work.

The bottom line is if you're not doing the miles to warrant a diesel.. Buy a petrol.
 

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F6HAD said:
Problem with that is the majority of drivers are not conscientious car enthusiasts like us who would be happy to make some manual intervention when prompted..

The majority of people don't get how cars work and just want them to work.

The bottom line is if you're not doing the miles to warrant a diesel.. Buy a petrol.

Will you be standing for parliament next term? I seem to recall the call from that lot a few years back was BUY DIESEL you know it makes sense. Personally if an MP TOLD ME IT WAS MY BIRTHDAY I would have to check my birth certificate before I believed him. LOL
 

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Who ever listens to any of the nonsense politicians spout anyway John
 
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