DPF Maintenance, worth it?
Discussion
I’ve picked up a cheap Mini diesel (N47) on 120K to play around with. No history but its got a new turbo, egr and a stage 1 map so its a bit of fun and costs nothing to run…. (Ok new bearings, discs, pads, calipers etc etc)
Bimmerlink shows the DPF is regenning regularly with oil ash at 39g. I have a couple of cans of DPF cleaner on the shelf unused and I’m trying to determine what or even if I should bother doing anything?
Please correct anything I’ve got wrong, I’m coming from a place of ignorance on this...
My understanding is that under ideal conditions a DPF should last 150K+, maybe more. The eventual failure being caused by the build up of oil ash restricting the flow of gasses through the DPF which creates pressure resulting in the car/engine producing error codes or going into limp mode etc.
Correct?
Oil ash builds up over the life of the DPF and is not removed or reduced by the the DPF performing regens. A regen reduces soot which builds more rapidly than oil ash but should not build to levels that are problematic if regens are performed as determined by the car. A regen burns off soot by increasing the temperature of the DPF by running the engine at higher rpm for a prolonged period.
Correct?
Premature failure or problems caused by the DPF are often due to regens not being performed as determined by the car causing soot levels to build. This can be mitigated by forcing a regen and/or using chemicals to help break down the soot and/or allow it to be burned off at lower temperatures.
Some additives also remove oil ash and can be used whilst the DPF is in situ as part of the regen process. Others require the removal of the DPF for the cleaning process.
Correct?
If I’m right so far a DPF subject to regular regens where soot levels are managed is not an issue until back pressure becomes problematic. This can be managed by reducing or removing the oil ash removal through cleaning.
However, soot and oil ash levels are largely calculated and not always actually measured. Therefore any figures shown by the ECU for for soot or oil ash levels may or may not be actually correct.
Therefore a real world indicator of DPF health is the pressure level before the DPF?
Correct?
On thie basis the above is not just made up drivel, 2 questions...
1) Is there any point in removing oil ash by whatever means without updating the ECU to reflect this? Or, is the ECU going to look at the pre-dpf pressure level to determine the DPF condition?
2) Irrispective of what the ECU thinks, is reducing the pre-dpf pressure a significant thing? Google says yes but is 1.01bar at idle really all that bad?
Any guidance appreciated.
Bimmerlink shows the DPF is regenning regularly with oil ash at 39g. I have a couple of cans of DPF cleaner on the shelf unused and I’m trying to determine what or even if I should bother doing anything?
Please correct anything I’ve got wrong, I’m coming from a place of ignorance on this...
My understanding is that under ideal conditions a DPF should last 150K+, maybe more. The eventual failure being caused by the build up of oil ash restricting the flow of gasses through the DPF which creates pressure resulting in the car/engine producing error codes or going into limp mode etc.
Correct?
Oil ash builds up over the life of the DPF and is not removed or reduced by the the DPF performing regens. A regen reduces soot which builds more rapidly than oil ash but should not build to levels that are problematic if regens are performed as determined by the car. A regen burns off soot by increasing the temperature of the DPF by running the engine at higher rpm for a prolonged period.
Correct?
Premature failure or problems caused by the DPF are often due to regens not being performed as determined by the car causing soot levels to build. This can be mitigated by forcing a regen and/or using chemicals to help break down the soot and/or allow it to be burned off at lower temperatures.
Some additives also remove oil ash and can be used whilst the DPF is in situ as part of the regen process. Others require the removal of the DPF for the cleaning process.
Correct?
If I’m right so far a DPF subject to regular regens where soot levels are managed is not an issue until back pressure becomes problematic. This can be managed by reducing or removing the oil ash removal through cleaning.
However, soot and oil ash levels are largely calculated and not always actually measured. Therefore any figures shown by the ECU for for soot or oil ash levels may or may not be actually correct.
Therefore a real world indicator of DPF health is the pressure level before the DPF?
Correct?
On thie basis the above is not just made up drivel, 2 questions...
1) Is there any point in removing oil ash by whatever means without updating the ECU to reflect this? Or, is the ECU going to look at the pre-dpf pressure level to determine the DPF condition?
2) Irrispective of what the ECU thinks, is reducing the pre-dpf pressure a significant thing? Google says yes but is 1.01bar at idle really all that bad?
Any guidance appreciated.
This is just my experience of just one car that I owned as it was my only diseasel that I looked into mostly for curiosity.
I would have though (based on the above relative ignorance) that 39g is quite a lot.
The one car I mention when I looked into the DPF calculations was only ever in the teens of grams.
Whether my assumption (based on a sample of one) is correct or not, I don't know.
Having said that if after my above experience I bought your car and did the same as you I would probably remove & clean it, clean/check the sensor hoses & check the sensor out using air pressure for confidence going forward.
But then (coming from a maintenance background) I am one of natures tinkerers/fixers & have time on my hands.
I would have though (based on the above relative ignorance) that 39g is quite a lot.
The one car I mention when I looked into the DPF calculations was only ever in the teens of grams.
Whether my assumption (based on a sample of one) is correct or not, I don't know.
Having said that if after my above experience I bought your car and did the same as you I would probably remove & clean it, clean/check the sensor hoses & check the sensor out using air pressure for confidence going forward.
But then (coming from a maintenance background) I am one of natures tinkerers/fixers & have time on my hands.
E-bmw said:
But then (coming from a maintenance background) I am one of natures tinkerers/fixers & have time on my hands.
This is my problem, too much time but not enough knowledge!I've been using it for work and figures from the past couple of weeks are not bad from a MPG perspective but tosday is a day off... already changed one caliper this morning.
Edited by 21TonyK on Wednesday 4th March 09:20
21TonyK said:
I ve picked up a cheap Mini diesel (N47) on 120K to play around with. No history but its got a new turbo, egr and a stage 1 map so its a bit of fun and costs nothing to run . (Ok new bearings, discs, pads, calipers etc etc)
Bimmerlink shows the DPF is regenning regularly with oil ash at 39g. I have a couple of cans of DPF cleaner on the shelf unused and I m trying to determine what or even if I should bother doing anything?
Please correct anything I ve got wrong, I m coming from a place of ignorance on this...
My understanding is that under ideal conditions a DPF should last 150K+, maybe more. The eventual failure being caused by the build up of oil ash restricting the flow of gasses through the DPF which creates pressure resulting in the car/engine producing error codes or going into limp mode etc.
Correct?
Oil ash builds up over the life of the DPF and is not removed or reduced by the the DPF performing regens. A regen reduces soot which builds more rapidly than oil ash but should not build to levels that are problematic if regens are performed as determined by the car. A regen burns off soot by increasing the temperature of the DPF by running the engine at higher rpm for a prolonged period.
Correct?
Premature failure or problems caused by the DPF are often due to regens not being performed as determined by the car causing soot levels to build. This can be mitigated by forcing a regen and/or using chemicals to help break down the soot and/or allow it to be burned off at lower temperatures.
Some additives also remove oil ash and can be used whilst the DPF is in situ as part of the regen process. Others require the removal of the DPF for the cleaning process.
Correct?
If I m right so far a DPF subject to regular regens where soot levels are managed is not an issue until back pressure becomes problematic. This can be managed by reducing or removing the oil ash removal through cleaning.
However, soot and oil ash levels are largely calculated and not always actually measured. Therefore any figures shown by the ECU for for soot or oil ash levels may or may not be actually correct.
Therefore a real world indicator of DPF health is the pressure level before the DPF?
Correct?
On thie basis the above is not just made up drivel, 2 questions...
1) Is there any point in removing oil ash by whatever means without updating the ECU to reflect this? Or, is the ECU going to look at the pre-dpf pressure level to determine the DPF condition?
2) Irrispective of what the ECU thinks, is reducing the pre-dpf pressure a significant thing? Google says yes but is 1.01bar at idle really all that bad?
Any guidance appreciated.
That is all largely correct. Soot builds up as a result of the combustion process and is converted to ash with regen. The ash stays there and there is not a lot you can do with it. Eventually you will reach the soot load limit and the filter has reached the end of it's life.Bimmerlink shows the DPF is regenning regularly with oil ash at 39g. I have a couple of cans of DPF cleaner on the shelf unused and I m trying to determine what or even if I should bother doing anything?
Please correct anything I ve got wrong, I m coming from a place of ignorance on this...
My understanding is that under ideal conditions a DPF should last 150K+, maybe more. The eventual failure being caused by the build up of oil ash restricting the flow of gasses through the DPF which creates pressure resulting in the car/engine producing error codes or going into limp mode etc.
Correct?
Oil ash builds up over the life of the DPF and is not removed or reduced by the the DPF performing regens. A regen reduces soot which builds more rapidly than oil ash but should not build to levels that are problematic if regens are performed as determined by the car. A regen burns off soot by increasing the temperature of the DPF by running the engine at higher rpm for a prolonged period.
Correct?
Premature failure or problems caused by the DPF are often due to regens not being performed as determined by the car causing soot levels to build. This can be mitigated by forcing a regen and/or using chemicals to help break down the soot and/or allow it to be burned off at lower temperatures.
Some additives also remove oil ash and can be used whilst the DPF is in situ as part of the regen process. Others require the removal of the DPF for the cleaning process.
Correct?
If I m right so far a DPF subject to regular regens where soot levels are managed is not an issue until back pressure becomes problematic. This can be managed by reducing or removing the oil ash removal through cleaning.
However, soot and oil ash levels are largely calculated and not always actually measured. Therefore any figures shown by the ECU for for soot or oil ash levels may or may not be actually correct.
Therefore a real world indicator of DPF health is the pressure level before the DPF?
Correct?
On thie basis the above is not just made up drivel, 2 questions...
1) Is there any point in removing oil ash by whatever means without updating the ECU to reflect this? Or, is the ECU going to look at the pre-dpf pressure level to determine the DPF condition?
2) Irrispective of what the ECU thinks, is reducing the pre-dpf pressure a significant thing? Google says yes but is 1.01bar at idle really all that bad?
Any guidance appreciated.
There are companies that will say you cleaners to remove the ash, but IMO, they are snake oil. The DPF is a filter by it's very nature, the ash is on the inlet side of the filter, the only way to correctly recover a DPF that has reached its ash load is to remove and back wash it to get the ash out through the inlet.
If yours is regen'ing correctly and not throwing warning lights, then leave it alone, putting some chemical in there to deal with the ash could risk messing the system up from it's current happy state.
shtu said:
Overall, you're massively overthinking it. You do realise those numbers are computer guesstimates? 
yeah... but Excel.... LOLProbably best left alone. Having my driveway done in the next month which will create a nice space for a 3rd mini which can be the one for playing with.
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