General DPF problems? hmmmm......

[rublehousen]

having read some of the posts about dpf problems/smoking/upgrades, and getting the basic idea of how this system works(i dont profess to know EXACTLY what im talking about so please feel free to correct me if you know better) ive been thinking a bit (yes...thats the burning smell)...

people generally buy a diesel for fuel economy. i suspect most of these drivers, as with probably 90% of volvo drivers, are sensible, easy on the throttle,look after the car and try to obtain max mpg type people. nothing wrong there. but, having mot'd lots of diesel engined cars, some of which were in top condition, looked after and cherished by their owners, i noticed that these were the ones that always failed on emissions test. they blasted soot out the back when revved up during testing(smoke meter reading off the scale) we would take them up the road and clear the soot with some high revs/ good thrashing. emissions would be spot on after that. another year of carefull driving and we would have to do the same again come mot time....

now, maybe(i dont know) volvo could have had reports/waranty claims of dpf problems ie, failing emissions,sooting up/blocked (possibly through careful economic driving styles) and has responded to dpf choking up with soot by increasing the fuel that stokes the fire to clean the filter(right?). maybe they think there is a problem with the system, not driving styles... sooooo,still with me?, volvo upgrade the software, more fuel is being used to clean the dpf, when the dpf is cleaned of all the soot...the software is still using an increased amount of fuel, which now MIGHT not be fully burning (because there might be a bit too much of it) in the clean dpf and especially if the dpf is not at full operating temperature. this will give you plumes of white smoke(i reckon anyway).
if i owned a diesel, i would regularly get it nice and hot and give it a thrash to clear the soot out, it does them good,especially when you have egr systems and stuff that help clog up intake manifolds and the like. this probly wont help AFTER this software upgrade, as you will still be getting too much fuel.
all of this might already have been discussed/blown out of the water, but i just thought i would share my opinion and hopefully be of a little help to someone. feel free to correct/educate me as i say, im not an expert on dpf's :-)

[Bill_56]

First, thanks for starting another DPF thread. It is clearly one of the main issues affecting modern Volvos, and the greater the visibility, and the more threads, the better. However you say you're not an expert and if you don't mind me saying so, it shows.

Taking the car for a thrash is completely pointless, unless you do so at a time the DPF needs regenerating, which can't be predicted. In fact it would be counter-productive to do so at any other time, as 'thrashing' the car would just add to the DPF's congestion.

When the DPF does need regenerating, you may not have access to a motorway to give it a 'thrash' (perhaps you're on a relaxed holiday?), or it may be winter with snow & ice that stops you driving fast, or you may be stuck in an M25 circular traffic-jam, or all manner of other things that could stop you taking the car 'for a thrash'.

Quite apart from all of that, DPFs are incompatible with bio-diesel blends, which is all that can be bought in the UK nowadays.

In order to understand the gravity of DPF problems, may I suggest you refer to the thread at:
http://www.volvoforums.org.uk/showthread.php?t=95323

[wimorrison]

@bill_56, I think that you are wrong about taking the car for a thrash.

The DPF only requires to forcibily regenerate when it is getting blocked, and that happens because the car has been driven on short journeys where the exhaust system has not had sufficient time to heat up the DPF. The DPF will clear the soot from the filter at any time when it gets hot enough.

Ergo, taking the car for a 'burn' up the road will prevent the need for forced regeneration.

Of cource the other way to prevent this issue - which is not unique to Volvo! - is not to use a diesel engined vehicle for short journeys.

[Bill_56]

Originally Posted by wimorrison

@bill_56, I think that you are wrong about taking the car for a thrash.

The DPF only requires to forcibily regenerate when it is getting blocked, and that happens because the car has been driven on short journeys where the exhaust system has not had sufficient time to heat up the DPF. The DPF will clear the soot from the filter at any time when it gets hot enough.

Sorry, but I disagree. My S60 owners manual states:

"The particles in the exhaust gasses are collected in the filter during normal driving. So called "regeneration" is started in order to burn away the particles and empty the filter. This requires the engine to have reached normal operating temperature."

"Regeneration of the filter takes place automatically at an interval 300-900km depending on driving conditions. Regeneration normally takes between 10 and 20 minutes. During this time fuel consumption may increase"

Does yours say something different?

[wimorrison]

My manual says the same, but I contend that an interval as wide and as varied as this specifies is normal motoring and as such does not constitute some specifally different action that is being undertaken. I define forced regeration as when you need to take the car on a journey which is not required as part of normal motoring to clear the DPF

The issue that people are having is not seen when the engine is driven on longer journeys where the exhaust system get hot, this is partly due to more efficient burning, partly due to the the regeneration happening, and is enhanced by having a hot exhaust system.

The soot warning happens when the car is driven regularly in cold conditions for short journey and it is then that you need to thrash the engine for 20mins plus to get the exhaust hot and undertake the forced regeneration, rather than normal driving regeneration.

[Bill_56]

Originally Posted by wimorrison

...The issue that people are having ...

Which issue are you referring to?

[wimorrison]

Originally Posted by Bill_56

Which issue are you referring to?

AFAIK there is only one - that is where the engine oil level increases becuase of the overfueling of the engine to clear the DPF. The excess diesel oil flows down into the sump.

That is the complaint that people have over the DPF, if this did not happen then people would be as aware of the DPF on diesel engine as they are of the CAT on a petrol engine.

[Bill_56]

There are other issues with DPF, such as the spectre of being told 'SOOT FILTER FULL. But let's leave that aside, if you wish.

As for the oil dilution, that will occur whenever the DPF regenerates. It makes no difference whether it is what you are calling a 'forced' regeneration (one that requires a special effort by the driver), or a 'normal' regeneration that goes unnoticed in the midst of a long high-speed derive. In both cases, extra fuel is post-injected, some of it sinks down into the sump, and if the fuel contains blended BIO-fuel (as all UK diesel now does), it will remain there, and accumulate over time.

There's quite good US website that covers the problem at:

http://savebiodiesel.com/index.html

[wimorrison]

Originally Posted by Bill_56

There are other issues with DPF, such as the spectre of being told 'SOOT FILTER FULL. But let's leave that aside, if you wish.

As for the oil dilution, that will occur whenever the DPF regenerates. It makes no difference whether it is what you are calling a 'forced' regeneration (one that requires a special effort by the driver), or a 'normal' regeneration that goes unnoticed in the midst of a long high-speed derive. In both cases, extra fuel is post-injected, some of it sinks down into the sump, and if the fuel contains blended BIO-fuel (as all UK diesel now does), it will remain there, and accumulate over time.

There's quite good US website that covers the problem at:

http://savebiodiesel.com/index.html

The problem is that it does not always go into the sump - many drivers, myself included, have had no issues with any excess oil in the sump. The drivers who have had the issues seem to be using the car for shorter journeys.

I have also looked into the DPF regeneration issues and it appears that the regeneration only happens when the filter is not cleared by normal driving, that is the car will inject additional fuel if the DPF is indicating that it needs cleaning. If it is getting hot enough to burn off the soot and contaminants the additional fuel is not injected to clean the DPF.

Being as most drivers are not having any issues with the DPF, and they are using the same diesel, it cannot be a fuel issue as intimated by you and others on the forums - if it was the fuel then everyone would have the issue. Similarly I think if it was the engine then again everyone would have the issue as the engines are the same.

The only things that are different in all cars are the driver, road conditions and driving style ergo, I believe that this is where the issue resides. Undoubtedly there may be issues where the use a diesel engine has been seen as advantageous may no longer be the case meaning that petrol engines may be the better choice for certain types of journey.

Clearly this is a difficult issue, at least going by the number of posts that are on these forums I am sure that there will be a definitive answer eventually

[rublehousen]

'If it is getting hot enough to burn off the soot and contaminants the additional fuel is not injected to clean the DPF.'

that was basically my assumption...go on...thrash it! :-)