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As I understand it (and there may be a bit of snake oil in here), the companies that do this are trying to resolve the issue whereby a DPF gets so full that it can no longer regenerate (i.e. burn off all the soot that's in it). They remove one of the sensors from the DPF and use the hole to inject some kind of detergent, which helps to break the soot down a bit so that regeneration can start again.
The smoke you are seeing is therefore a mixture of soot, burned soap and, eventually, ash.
I don't think it's wise to start putting soap in a DPF, but I suppose it will turn the light out for a bit and either make you think it's fixed or give you time to sell the car.
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Hilarious if all we are doing is bottling up the particulates only to release them in one go, although I am assuming its not quite that simple..
Assuming the particulates are mainly carbonaceous and captured in the small interstices of the filter, the only way of removing them is to burn them into CO2.
(Elemental carbon is not, as far as I know, soluble in any liquid that would not seriously attack steel, one such is boiling concentrated sulphuric acid)
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It depends on the form the carbon is in. C60 will dissolve in carbon disulphide.
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Speculative, but I recently used brake fluid to clean my spark plugs. I doubt it dissolved-what looked like elemental carbon, but along with fluid pressure from a syringe, it certainly seemed to be an effective dispersant.
People used to use oxygen to decoke 2 stroke exhausts
Get it cooking on oxy-acetylene, then switch to pure O
There was a risk of meltdown, which might also apply to a DPF
Edited by edlithgow on 23/03/2023 at 00:35
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The matrix inside a DPF is platinum (which is why they get nicked). The carbon gets bonded to the matrix and the only way to remove it is to burn it off at approx 600 degrees, this is what a regen does.
Carrying out an "italian tune up" will never work because its not a ECU controlled regen and if your revs are too high the faster gas speed will again not allow the temp to rise high enough. When we had the Kia they stated your revs during a regen should be between 1600 and 2000 (2000 was about 60mph in 6th). We tried a regen at 70 mph and one at 60 mph, the one at 60 mph completed far quicker (sort of proving the recommendations).
Heavy plant DPF's are removed for regens when they are severely blocked but its an expensive and lengthy process involving heating the dpf to 600 degreee and blowing air (or it might be air diesel mix) through it. Its worth it on expensive plant but not on a cheaper car DPF.
As far as I am aware all the chemicals that clean DPF either work for a short time or not at all.
And nothing gets rid of the ash that is created during a regen, it is that which eventually kills the DPF.
Best advice is to read your manual and follow the instructions. All manufacturers are different but all simply ask you to drive normally. None of this revving the nuts off the car to blow the soot out nonsense.
We had cars with DPF's from 2006 to 2015 and did not have a single issue in about 130,000 miles. But they were used more or less daily on dual carriageways or motorways (my commute had about 7 miles of such road, the wifes about 14 miles) and when we were doing short urban runs we tried to use the petrol Micra whenever possible.
There is loads of nonsense on forums or the web generally, follow this advice at your peril.
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I think you are mixing up dpfs and catalytic converters, the latter containing exotic metals as the catalyst.
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I think you are mixing up dpfs and catalytic converters, the latter containing exotic metals as the catalyst.
Correct, having a bad day. The matrix is made up of something equally tough to trap the particles and withstand 600 degrees, not sure what it is though.
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I think you are mixing up dpfs and catalytic converters, the latter containing exotic metals as the catalyst.
Correct, having a bad day. The matrix is made up of something equally tough to trap the particles and withstand 600 degrees, not sure what it is though.
I THINK you were actually correct the first time. As I understand it, passive regeneration has to occur at the lower temperatures that might be achieved in normal operation, and so requires a catalyst to promote oxidation.
The filter matrix is an array of ceramic tubules, half open at the input end, (these ones collect the soot) half at the ouput end.(these ones allow the escape of the filtered exhaust gases).
It occurs to me (as a theoretical possibility) that if you could swap ends you might blow quite a lot of the soot out, which would be very bad environmentally, but might extend your DPF life quite a bit..
It also occurs to me that the design might make wet back-flushing rather inneffective, since there are no open channels, It could only work if the filter medium is permeable to water, and I don't know if it is, or how much.
Of course Its known to be permeable to gases, so compressed air should work, but then you are back to blowing soot around.
Edited by edlithgow on 25/03/2023 at 03:36
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It occurs to me (as a theoretical possibility) that if you could swap ends you might blow quite a lot of the soot out,
The DPF is designed so that the soot particles (the particulates) are bonded to the matrix and can only be removed at high temp by converting them into ash etc. Simply being able to blow them out would rather defeat the object of collecting them and "safely" converting them.
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It occurs to me (as a theoretical possibility) that if you could swap ends you might blow quite a lot of the soot out,
The DPF is designed so that the soot particles (the particulates) are bonded to the matrix and can only be removed at high temp by converting them into ash etc. Simply being able to blow them out would rather defeat the object of collecting them and "safely" converting them.
Simply being able to blow them out would only rather defeat the object of collecting them and "safely" converting them, if a lot of people were simply blowing them out into the general environment.
Terry and June aren't going to be doing that on any scale, but that doesn't mean it isn't possible.
Similarly, the fact that I can't think how one could "bond" soot to a matrix, doesn't mean it isn't possible either, but it does make me rather reluctant to believe it without some actual evidence.
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Simply being able to blow them out would only rather defeat the object of collecting them and "safely" converting them, if a lot of people were simply blowing them out into the general environment.
The particulates are carcinogenic and anyone simply "blowing them out" (even if it were possible) would be putting themselves at risk.
Similarly, the fact that I can't think how one could "bond" soot to a matrix, doesn't mean it isn't possible either, but it does make me rather reluctant to believe it without some actual evidence.
The only evidence of this I had was the info sheet that came with the Kia Ceed CRDi we bought in 2010. Ours was a MY11 car and previous years did not use a DPF unless it was a 2 litre. I guess Kia were trying to help us understand what it did and providing you drove normally you were unlikely to have any issues.
But if it were not bonded surely the soot would simply blow out the back when you floored it (just like it did in older diesels) but I know for a fact this did not happen. This is why 600 degrees is required to burn the particles off.
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But if it were not bonded surely the soot would simply blow out the back when you floored it (just like it did in older diesels) but I know for a fact this did not happen. This is why 600 degrees is required to burn the particles off.
Its a filter.
Filters do not generally "bond" to the filtrant (i.e. the stuff that is retained in the filter *).
Your air filter, for example, does not "bond" to the dust it retains, its simply physically stopped by the filter matrix, which has interstices that are smaller than the dust particles retained (smaller particles may come through).
If you floored it, you should not get a significant amount of the retained dust coming through into your engine .
OTOH if you back-flushed it with compressed air, you would blow some dust off the outside surface of the filter into the atmosphere.
I currently have no reason to believe the DPF is different in this respect. Some soot particles will penetrate some distance into the ceramic pore matrix where they may be trapped (not, AFAIK "bonded") but the bulk of the soot will be in a surface "filter cake" lining the inside of the receiving tubules.
Whether back flushing would work (with a gas or a liquid) I'm not sure. It seems possible, but it also seems possible that the entry tubules would clog if back flushed, since all the displaced soot would have to traverse the length of the tubule before exiting.
(*According to the Internyet, filtrant is not an English word. Knock me dahn wiv a fevva. I was almost sure it was when I did my chemistry at school. Filtrant: stuff retained, filtrate: stuff that comes through. But apparently not. Should be filtride, which I don't remember ever using.)
Edited by edlithgow on 26/03/2023 at 16:04
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Further to the above, you do get "bonding" in some filtration applications. For example, ionic bonding with solute gradient elution is used routinely, along with molecular sieving ("Sephadex") in protein purification, and activated charcoal is used in gas mask filters to adsorb nerve gases and such.
The last does suggest that elemental carbon, at least in some forms, could "bond" (not in this case actual covalent bonding, but an adsorption involving weaker intermolecular forces like hydrogen bonds) to a matrix.
However, I doubt (could easily be wrong) its a significant mechanism in DPF filtration because of the "fluffy" nature of soot particles, which would likely mean that only a small proportion of carbon atoms, those on the surface of the particle, would be available for such adsorption.
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People used to use oxygen to decoke 2 stroke exhausts
Caustic soda in my day.
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People used to use oxygen to decoke 2 stroke exhausts
Caustic soda in my day.
Suppose it depends what you've got access to
Most garages probably have oxy-acetylene on hand, and most punters don't, plus Terry and June might call the cops.
Caustic soda is fairly dangerous though, and, as noted above, probably won't affect "elemental carbon" directly.
Oxygen will.
An ash residue might be partly removed by a soak (acidic? alkaline?) and back-flushing.
Re "deviate from the manufactures advice at your peril", one always does everything (or nothing) at ones peril. Following manufacturers advice on CVT maintenance, for example, is known to be perilous, but IF there are Dodgy DIY DPF techniques out there on't Nyet, (dunno, no evidence here) its a fair bet no one is going to be trying them on new cars in warranty.
This will be for possible end-of-life extension where there is little or nothing to lose (provided you don't maim yourself, of course)
Advice from a 3rd Party DPF recovery service, OTOH, is likely to be just as self-serving as that from any other commercial entity,
Edited by edlithgow on 24/03/2023 at 02:11
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