DPF removal

[Rick101]

For those that drive slow dirty diesels, what's the impact of DPF removal?

I had a stage 1 map on my Octavia a while back but kept the filter in situ. I wondering what the pro's and con's are of having it removed.

Technician advises their mapping will ensure emissions will fall within current MOT requirements.

I'm more concerned about future MOT requirements, which of course they can't guarantee, but thats no help to me.

Any advice?

[Andyjc86]

The way I know garages doing it, is to take the DPF off, knock out the internals, send the ecu off to have the DPF electronically removed, refit, drive for 4 hours (not sure why), give back to customer.

It seems to work well, I've not known any of the cars coming back again.

[NotDave]

I've been pondering the same. But one idea is to remove but keep it safe, then should such need arise, reinstate it.

[Rick101]

Think I'll leave it in situ unless/until it becomes a problem

[Mikey G]

The DPF only works on cold starts untill the engine warms up. It serves no other purpose once the car is up to temperature. So MOT time there shouldnt be an issue as long as the car is properly warmed up before the emissions test.
Most people just knock the internals out. You can get complete removal pipes if you wish to keep the DPF but to put it back on you would have to re install the old map or you could get back pressure problems as the ECU would no longer know its there.

[Krikkit]

The DPF works all the time, not just when the engine is cold. The EGR is only used when cold, to reduce NOx emissions.

Edited by Krikkit on Wednesday 3rd April 10:40

[CraigyMc]

Mikey G said:

The DPF only works on cold starts untill the engine warms up. It serves no other purpose once the car is up to temperature.

Eh? The DPF works all the time the engine is running.

I thought the DPF only did a regen on steady state stuff. Are you mixed up?

DPF: Diesel Particulate Filter.

C

[Mikey G]

CraigyMc said:

Eh? The DPF works all the time the engine is running.

I thought the DPF only did a regen on steady state stuff. Are you mixed up?

DPF: Diesel Particulate Filter.

C

No i'm not mixed up...
The DPF is always there and does a little work but not a lot when fully upto temperature. Yes they regen in steady state as you say taking the filter upto 800 degrees when on a long steady run to burn off the soot, So at that point it is not working to reduce the cars emissions.

I have spent time doing emergency regenerations in a few cars now with diagnostic equipment to perform it. All the time monitoring the soot content and exhaust temps. My observations were that during normal driving the DPF was only gathering noticable soot during the first 10-15 minutes of running and after that it was regulating the soot content without regenerating once all up to normal running temps. Its the short cold runs that fills it up, if you drove the car all day around town it wont increase but it wont ever empty, thats why they need a motorway run.

[dmitsi]

Mikey G said:

CraigyMc said:

Eh? The DPF works all the time the engine is running.

I thought the DPF only did a regen on steady state stuff. Are you mixed up?

DPF: Diesel Particulate Filter.

C

No i'm not mixed up...
The DPF is always there and does a little work but not a lot when fully upto temperature. Yes they regen in steady state as you say taking the filter upto 800 degrees when on a long steady run to burn off the soot, So at that point it is not working to reduce the cars emissions.

I have spent time doing emergency regenerations in a few cars now with diagnostic equipment to perform it. All the time monitoring the soot content and exhaust temps. My observations were that during normal driving the DPF was only gathering noticable soot during the first 10-15 minutes of running and after that it was regulating the soot content without regenerating once all up to normal running temps. Its the short cold runs that fills it up, if you drove the car all day around town it wont increase but it wont ever empty, thats why they need a motorway run.

A DPF is active at all temperatures all of the time. It doesn't switch on or off. Although it may do more work on a colder engine as higher levels of soot/HC could be produced whilst the engine warms up, soot levels do not disappear when an engine is up to temp and the filter is always collecting the exhaust. The engine speed and load will change the amounts of soot being produced. The reduction in particulates you see at higher speed and loads is a by-product of the vehicles efficiency at these conditions. When an engine is running at high temps for prolonged times the DPF will carry out passive regeneration, usually when the DPF is 45% 'full'. As a lot of diesels don't get used at these conditions we have to include active regeneration. The DPF will monitor how 'full' it is and when the limit is reached, regen is required. If a car is regularly being used at high temps this limit will rarely be passed. If however it is used for short journeys the active regen will come into play. This is acheived by adjusting the fueling to increase the exhaust temps and force a regen. The problem with this is that sometimes it starts and the engine is stopped before it has time to complete. Then when the engine is next started more soot is created and so the DPF fills more, the serious issues occur when a DPF gets close to 75% full without a chance to regen and then it'll need to go to a garage for a forced regen. People who own diesels for a 3 minute drive to the shops have this problem.

The comment above about EGR only being active when cold is incorrect. EGR rate will vary with speed and load, but will only ever be off at full load conditions. Once an engine is up to temp the EGR does not stop, as even when warm the emissions are still there and can be controlled with use of EGR.

Edited by dmitsi on Wednesday 3rd April 11:37

[Krikkit]

dmitsi said:

The comment above about EGR only being active when cold is incorrect. EGR rate will vary with speed and load, but will only ever be off at full load conditions. Once an engine is up to temp the EGR does not stop, as even when warm the emissions are still there and can be controlled with use of EGR.

Edited by dmitsi on Wednesday 3rd April 11:31

Well colour me educated - I thought the EGR was a cold-only measure for the peak NOx production time.

[dmitsi]

Krikkit said:

Well colour me educated - I thought the EGR was a cold-only measure for the peak NOx production time.

Active at all the temps, and the rate will vary on coolant/oil temp, so the maps being used when cold might call for a higher rate of EGR. In addition to my above point, the EGR can also close when at prolonged period of idle.

[Evoluzione]

Krikkit said:

Well colour me educated - I thought the EGR was a cold-only measure for the peak NOx production time.

EGR is also an economy device, it feeds in used gasses on cruise, the ECU then reduces the amount of diesel injected for more MPG.

[Evoluzione]

Rick101 said:

For those that drive slow dirty diesels, what's the impact of DPF removal?

I had a stage 1 map on my Octavia a while back but kept the filter in situ. I wondering what the pro's and con's are of having it removed.

Technician advises their mapping will ensure emissions will fall within current MOT requirements.

I'm more concerned about future MOT requirements, which of course they can't guarantee, but thats no help to me.

Any advice?

I think you are getting two things mixed up, DPF removes particulates, it's not a gaseous cleaner like a Cat so is't anything to do with gas emissions.
You can remove the DPF if you want to pollute the atmosphere we have to live in and a good condition standard car will still pass an MOT, as has been said, you need to re-program the ECU.
It may be that the re-map or excessive wear has caused more soot to be produced, it may not....

Lets say on a scale of 1 - 10 with a DPF fitted your car scores 10, with it removed it scores 5 so will still pass if the fail is 4 or less.

Pros: Less restriction = more power.
Cons: Your selfish behaviour would make a worse environment for the rest of us.

[HannsG]

I'm looking to remove the DPF on my Saab 9-3 Ttid. It should help avoid the "limited performance" errors which are an issue if using the car on short journeys.

DPF + EGR blanking and a remap are around £540 in my area...

Well worth it for the extra peace of mind, power and increase in mpg

[r11co]

Evoluzione said:

Cons: Your selfish behaviour would make a worse environment for the rest of us.

Hmmm. Trace the history of emission controls on vehicles and you will see that the ones that became compulsory have almost invariably had the backing of fuel companies who have taken up the options of the back of the 'think of the children' argument despite alternatives existing that would give more benefit with significantly lower fuel consumption. Catalytic converters and DPFs specifically use fuel in their operation - fuel that isn't being used to propel the vehicle and therefor lowering the vehicle's efficiency in terms of what it is supposed to do.

I do not support the use of these devices in any way as they have been imposed in order to stifle other developments that would have given far greater environmental benefits but harmed the fuel industry, such as lean burn technology (effectively halted by the stoichiometric requirements of catalytic converters) and cleaner diesel.

[Willy Nilly]

Removing the DPF is effectively fly emitting particulate matter in the atmosphere

[karl957]

I had my dpf removed in my 5 series last year and I have to say i regretted it.

At the time given, the choice between a £1500 DPF 'service' (in BMW speak) or 'Replacement' to you and me, and a £500 DPF removal, ECU delete and Remap, I opted for the latter.

Yes I was a grand better off and the increased performance was great but the smoke coming out of the back (especially on cold starts) made me feel as though the car was worth a grand less. Also the economy remap caused my auto box to keep changing up too soon and i end ed up driving in manual mode most of the time. I hoped having the dpf out and remap would make me want to keep the car for another year or so but in the end i traded it in for something else. I'm not sure what impact it had on the trade in price but if i was buying it private, it would have put me off.

My advice is if you're not having any problems with it failing to regen or going into limp mode, leave well alone. IF you do decide to go for it, do your research and get advice and recommendations from somebody who's had it done on the same car as yours.

Hope this helps

[NotDave]

HannsG said:

I'm looking to remove the DPF on my Saab 9-3 Ttid. It should help avoid the "limited performance" errors which are an issue if using the car on short journeys.

DPF + EGR blanking and a remap are around £540 in my area...

Well worth it for the extra peace of mind, power and increase in mpg

Any chance you could PM me the name/location of who's offering this?

I have the same car (150bhp - 2006 variant) and at 100k miles, the EGR is a worry, as our lass uses the car like a nun, pootling everywhere at 60mph on CC. I have to give it a weekly warm up/abuse/cool down loop to try and avoid the dreaded issues.

[Rick101]

Evoluzione said:

Rick101 said:

For those that drive slow dirty diesels, what's the impact of DPF removal?

I had a stage 1 map on my Octavia a while back but kept the filter in situ. I wondering what the pro's and con's are of having it removed.

Technician advises their mapping will ensure emissions will fall within current MOT requirements.

I'm more concerned about future MOT requirements, which of course they can't guarantee, but thats no help to me.

Any advice?

I think you are getting two things mixed up, DPF removes particulates, it's not a gaseous cleaner like a Cat so is't anything to do with gas emissions.
You can remove the DPF if you want to pollute the atmosphere we have to live in and a good condition standard car will still pass an MOT, as has been said, you need to re-program the ECU.
It may be that the re-map or excessive wear has caused more soot to be produced, it may not....

Lets say on a scale of 1 - 10 with a DPF fitted your car scores 10, with it removed it scores 5 so will still pass if the fail is 4 or less.

Pros: Less restriction = more power.
Cons: Your selfish behaviour would make a worse environment for the rest of us.

No not mixed up, though you seem to be.

Your idiotic comments make places like this a worse place to be.

Thanks to all others for the advice.

[Evoluzione]

Willy Nilly said:

Removing the DPF is effectively fly emitting particulate matter in the atmosphere

What do you mean like fly-tipping?