Author Topic: Understanding DPF Regens  (Read 8892 times)

Offline Optimus prime

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Understanding DPF Regens
« on: 02 August 2015, 17:46 »
Guys,

Having a full copy of VCDS I have been monitoring my car's regens etc & logging the results.  In a nut shell the results and regen conditions are below:  These tests have been on normal diesels but I am now running on BP ultimate to see if any thing differs.

Car regens every 500 miles approx
During a regen the stop/start fails to operate
Car idle's at just over 1000 rpm instead of 800

Fans running after the car has been turned off is the sign of a very recent completed regen & is part of the cool down process.  It does not happen during the regen as heat needs to be maintained for the process to complete.

Hope this helps

Offline topher

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Re: Understanding DPF Regens
« Reply #1 on: 02 August 2015, 19:16 »
The regens aren't mileage dependent they're triggered when the carbon mass reaches a certain limit. If the appropriate conditions aren't met during driving and the regen can't start or is shut off before it can complete there is another trigger level for the dpf warning light to come on telling you to go thrash the car so it can run a regeneration routine.
If the light is ignored the final trigger level will put on the engine management light and usually a flashing glow plug light along with limp mode meaning the dpf will need a forced regeneration.. then there is the "safety" carbon mass level at which point the car and/or diag tools will reject the forced regen due to risk of fire (although there is still a way to trick it in to working). It should never really get to that final stage though unless there is a fault somewhere else in the engine that is ignored... anything that messes with the airflow through the engine so throttle body, egr valve, intake runners and boost leaks are the usual culprits along with faulty pressure sensor or temp sensors in the dpf.

Offline Optimus prime

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Re: Understanding DPF Regens
« Reply #2 on: 02 August 2015, 19:32 »
The regens aren't mileage dependent they're triggered when the carbon mass reaches a certain limit. If the appropriate conditions aren't met during driving and the regen can't start or is shut off before it can complete there is another trigger level for the dpf warning light to come on telling you to go thrash the car so it can run a regeneration routine.
If the light is ignored the final trigger level will put on the engine management light and usually a flashing glow plug light along with limp mode meaning the dpf will need a forced regeneration.. then there is the "safety" carbon mass level at which point the car and/or diag tools will reject the forced regen due to risk of fire (although there is still a way to trick it in to working). It should never really get to that final stage though unless there is a fault somewhere else in the engine that is ignored... anything that messes with the airflow through the engine so throttle body, egr valve, intake runners and boost leaks are the usual culprits along with faulty pressure sensor or temp sensors in the dpf.

Hi,

Yes I am aware of all the criteria thank you, having driven diesels for over 15 yrs most with dam DPF's!  The mileage I quoted was simply a guide as to how my car regens based on its use of only a 28 mile round trip everyday.  The soot loading is the factor as you state but it will be interesting to see if by using a super fuel if the the regens take place at a higher mileage interval or indeed less frequent? 

Also I plan to fit a DTUK box at some point and then do this research again as some have said that these boxes have also reduced the number of regens although I am a little sceptical on this as in my experience any typical form of engine mapping / enhancement tends to increase soot loading. 

By the way "thrashing" is not required a steady 20 min run in sports mode (with a higher gear) with the rev's above 2000 rpm will do the trick, & just wait for the light to go out.  Or use VCDS and start a standing/idle regen process & go and put the kettle on!
« Last Edit: 02 August 2015, 19:37 by Optimus prime »

Offline topher

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Re: Understanding DPF Regens
« Reply #3 on: 02 August 2015, 20:07 »
Was merely pointing out that not everyone can base their regen frequency on your own particular daily drive, some people (who don't really need a diesel) will be doing far less miles and with low speed stop/start driving. I would be very surprised if you ever see your own dpf dash light come on.
I see little to no difference with these so-called super fuels when it comes to frequency of regens, they do seem to help the process complete a little faster though. Poorly refined remaps certainly lead to increased soot loads but those that burn clean tend not to have any negative effects. I've never played with the DTUK boxes but I know they are superior to the oldskool resistor boxes which just overfuel and lead to premature dpf failure.
Thrashing is subjective, holding a diesel for prolonged periods over 2000rpm is counter-intuitive to most. 50mph in 4th gear at steady load I find works best.. I would also advise against using the emergency forced regen unless absolutely necessary as it will shorten the life of the dpf, allowing the ash content to build up faster than normal.

Offline Optimus prime

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Re: Understanding DPF Regens
« Reply #4 on: 02 August 2015, 20:30 »
Was merely pointing out that not everyone can base their regen frequency on your own particular daily drive, some people (who don't really need a diesel) will be doing far less miles and with low speed stop/start driving. I would be very surprised if you ever see your own dpf dash light come on.
I see little to no difference with these so-called super fuels when it comes to frequency of regens, they do seem to help the process complete a little faster though. Poorly refined remaps certainly lead to increased soot loads but those that burn clean tend not to have any negative effects. I've never played with the DTUK boxes but I know they are superior to the oldskool resistor boxes which just overfuel and lead to premature dpf failure.
Thrashing is subjective, holding a diesel for prolonged periods over 2000rpm is counter-intuitive to most. 50mph in 4th gear at steady load I find works best.. I would also advise against using the emergency forced regen unless absolutely necessary as it will shorten the life of the dpf, allowing the ash content to build up faster than normal.

Yes I agree I could probably do without a diesel but the torque is just great  :smiley:  I have noticed an increase of 4 mpg over my normal journey using bp ultimate but shell nitro + was no different over normal fuel.  It will be interesting to see if the regens are a little less frequent or more spaced out on ultimate, traditionally I would go for a decent obd remap from Emaps as he has done all my cars in the past and can do the mk7 but I still have over 2 yrs warranty left & as you we all know sometimes " if you play you pay" espically if your unlucky enough to have a large engine or gearbox claim.

Yes the emergency dpf regen process is exactly that if really necessary I would program the regen while driving process instead.  However as these cars give you some indication via the dash light it is much easier to sort out unlike BMW diesels where the dpf light is an indication all to late !
« Last Edit: 02 August 2015, 20:37 by Optimus prime »

Offline mcmaddy

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Re: Understanding DPF Regens
« Reply #5 on: 03 August 2015, 08:38 »
I wouldn't worry about the dpf and just drive the car. I've never had any light or problems with the dpf and I do 3 miles to work and 3 miles back 5 days a week. Mine seems to regen every 800 miles or so no matter what the driving conditions are (it started doing one after I'd driven to the Isle of Skye). These new diesel engines are nothing like the old ones so stop worrying about the dpf.
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Offline Optimus prime

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Re: Understanding DPF Regens
« Reply #6 on: 03 August 2015, 08:42 »
I wouldn't worry about the dpf and just drive the car. I've never had any light or problems with the dpf and I do 3 miles to work and 3 miles back 5 days a week. Mine seems to regen every 800 miles or so no matter what the driving conditions are (it started doing one after I'd driven to the Isle of Skye).

Not worrying I know enough about them, just passing on my little knowledge to those that may not.  People need to be aware because up until the MK7 when they moved the dpf closer to the engine things were not so good.  Prevention is better than cure.

Offline mcmaddy

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Re: Understanding DPF Regens
« Reply #7 on: 03 August 2015, 08:44 »
Totally agree but I doubt you'll even need to do anything with this dpf on your mk7.
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Offline fredgroves

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Re: Understanding DPF Regens
« Reply #8 on: 03 August 2015, 09:05 »
I did read somewhere that a low fuel level can also inhibit the regen cycle?

Not sure if that's what the Golf logic works like though?
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Offline Optimus prime

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Re: Understanding DPF Regens
« Reply #9 on: 03 August 2015, 09:05 »
Totally agree but I doubt you'll even need to do anything with this dpf on your mk7.

No I think you right having spent many years fighting and fixing DPF's issue's on BMW's it would be nice to have a break  :smiley: BMW software (DIS) is so unfriendly & clunky to use, VCDS is a breeze compared