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View Full Version : DPF regeneration..according to Audi



Greg Roles
11-08-2008, 01:34 PM
Found this today on the AU Audi site. Last part mentions active regen as often as each 1000k! I've noticed the higher idle around 1000rpm several times now, and I assume this is indeed the active regeneration cycle. Need to get me EGR hooked up to be sure.

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A diesel particulate filter is a system for removing diesel particulates from diesel exhaust. Audi uses a system that exploits the most advanced state of the art: the "catalysed soot filter" (CSF for short) has a filter coating containing precious metals which acts in two ways. The passive regeneration process involves the slow, environment-protecting conversion of the particulates deposited in the catalytic converter into CO2. This process takes place within a temperature range of 350 - 500 degrees and occurs continuously without any special measures being required, predominantly when the car is being driven at motorway speeds.

Only if the car is used for any length of time at low loads, for instance in urban traffic, is the temperature of the exhaust gas actively raised to around 600 degrees every 1,000 to 1,200 kilometres, to prompt additional regeneration of the filter. The particulates captured in the filter burn off at this temperature.

gldgti
13-08-2008, 12:26 PM
so from what i can gather, the dpf works like a slow combustion stove.... trapping the soot (carbon) and allowing it to burn inside the dpf to form C02. since diesels pump plenty of excess oxygen under normal consitions, theres plenty in the exhaust to support this combustion process.

as you block up the system, i would guess that exhaust pressure sensors on either side of the dpf indicate that "regeneration" or more accurately 'burn off' is required. i would guess that then the ecu adjusts the fuel maps to run excessive boost, thereby supplying extra 02 to pass through the exhaust system and aid to burn the built up carbon.

remembering that with a diesel, power output is a function of how much fuel you are able to burn in a stroke, NOT dependant on boost pressure, per-say. the burn off phase would equate to a "lean" running condition, not really applicable to diesels, buth the analogy stands.

Logzy
13-08-2008, 01:09 PM
I've noticed the higher idle around 1000rpm several times now, and I assume this is indeed the active regeneration cycle.

+1 .

Russ59
25-09-2008, 06:57 PM
Anyone happen to know what would happen if the car decides to do this whilst still not at operating temperature ?? I had an incident with mine today where I had driven around 70 km's turned the car off and returned a couple of hours later. I started the car as normal but it appeared to be running a bit a rough and I was having to rev it more than usual to take off. I had to stop and start at a few sets of traffic lights on a couple of hills and it didn't like it very much and appeared to a bit jerky on take off, I then had to stop at another set of lights and it was at that stage idling at 1000 rpm (200 rpm higher than usual) it was still not quite at operating temperature and when I went to take off it wouldn't rev and stalled. I had my foot on the clutch and when I tried to start the car it was dead ( lights were on but nothing happened when I turned the key) nearly ended up with a Rav 4 up my ar$3. I turned the key off and then back on again, it started and I drove off again having to use more accelerator than usual as it wasn't running right. I stopped a few k's along when I could get off the road and it was still idling at 1000 rpm and was jerky on take off and still needing a bit more throttle than usual. By the time I got another couple of K's along the idle had dropped to normal again but the car was still feeling jerky especially when backing off the throttle and slowing down through the gears. :frown:

Russ

gerhard
25-09-2008, 07:13 PM
Anyone happen to know what would happen if the car decides to do this whilst still not at operating temperature ?? I had an incident with mine today where I had driven around 70 km's turned the car off and returned a couple of hours later. I started the car as normal but it appeared to be running a bit a rough and I was having to rev it more than usual to take off. I had to stop and start at a few sets of traffic lights on a couple of hills and it didn't like it very much and appeared to a bit jerky on take off, I then had to stop at another set of lights and it was at that stage idling at 1000 rpm (200 rpm higher than usual) it was still not quite at operating temperature and when I went to take off it wouldn't rev and stalled. I had my foot on the clutch and when I tried to start the car it was dead ( lights were on but nothing happened when I turned the key) nearly ended up with a Rav 4 up my ar$3. I turned the key off and then back on again, it started and I drove off again having to use more accelerator than usual as it wasn't running right. I stopped a few k's along when I could get off the road and it was still idling at 1000 rpm and was jerky on take off and still needing a bit more throttle than usual. By the time I got another couple of K's along the idle had dropped to normal again but the car was still feeling jerky especially when backing off the throttle and slowing down through the gears. :frown:

Russ

I think you have a different problem.

gerhard
25-09-2008, 07:15 PM
so from what i can gather, the dpf works like a slow combustion stove.... trapping the soot (carbon) and allowing it to burn inside the dpf to form C02. since diesels pump plenty of excess oxygen under normal consitions, theres plenty in the exhaust to support this combustion process.

as you block up the system, i would guess that exhaust pressure sensors on either side of the dpf indicate that "regeneration" or more accurately 'burn off' is required. i would guess that then the ecu adjusts the fuel maps to run excessive boost, thereby supplying extra 02 to pass through the exhaust system and aid to burn the built up carbon.

remembering that with a diesel, power output is a function of how much fuel you are able to burn in a stroke, NOT dependant on boost pressure, per-say. the burn off phase would equate to a "lean" running condition, not really applicable to diesels, buth the analogy stands.

Mostly correct, but I believe the extra heat is created in the exhaust by supplying MORE fuel, not less.

Diesels are highly sensitive to overfuelling, to the extent that pistons will burn if overfuelling is consistent, such as you might get in a poorly tuned Cruiser diesel with aftermarket turbo.

Greg Roles
25-09-2008, 09:16 PM
I've a whole tech bulletin on it, and I do seem to recall something about late injected fuel timing so it ignites in the DPF, thus heating it up to burn off the extra soot. Can't be @rsed looking right now sorry!

VW also mention that the DPF will progressively get blocked from the rear forwards, so it's a throw away item at some stage. I doubt it will be a cheap part!

Russ, that sounds exactly like the regen cycle, everything but the jerkyness / lack of power. I've turned the car off mid DPF regen before, and found it wants to do the typical 10 mins regen cycle all over again on hot restart, but I've yet to do a cold start, where I do assume it would do the same thing.

I've found that apart from the increased idle, the car still drives as per normal, and still goes like the clappers if you up it. When it's hot anyhow!

I would guess that a regen / late injection cycle on a cold start could make the car run poorly, so let us know if it's back to normal tomorrow.

You always have to turn the key all the way off to restart it too mate, quite embarassing to stall it in peakhour, but I think all us manual oilers have been there...several times:biggrin:

Russ59
25-09-2008, 10:24 PM
Hey Greg,

I sent an email through tonight to the salesman and have asked him to forward on the details of the symptoms to the service dept. for me and ask them if they have any idea on the cause. I am guessing from what I have read about the DPF regeneration cycle that it may be responsible for what I experienced cause I'm pretty sure it wasn't my driving as I am used to the clutch now and having to give it a few revs to take off. I'll keep you all posted !!

Cheers
Russ

gregozedobe
25-09-2008, 10:52 PM
..... and when I went to take off it wouldn't rev and stalled. I had my foot on the clutch and when I tried to start the car it was dead ( lights were on but nothing happened when I turned the key) nearly ended up with a Rav 4 up my ar$3. I turned the key off and then back on again, it started

Russ,

I can't help you with your rough running problems, as I haven't experienced anything like it. My Transporter has a DPF, but as it does nearly 100% highway driving, it has probably never needed to "regenerate".

I can say that what happened when you stalled your engine is 100% as intended by VW. You must switch it off completely before you can operate the starter motor again. Just to hazard a guess it is to stop people trying to run the starter motor when the engine is already running (as if anyone could NOT notice that their TDI was already running :) ). IIRC it is detailed somewhere in the owner's manual.

Greg Roles
26-09-2008, 06:26 AM
I'd have to second that, as I'm finding blasting around in the city my diesel is regenerating every few weeks.

Russ, good luck mate, and if your car continues to run rough you could always consider unhooking the battery for a good hour and seeing if this defaults the car back to zero....then again i guess the DPF will still be sending pressure differences and wanting to start a recycle if it is indeed blocked, and it'll happen all over again!

Anyone near you have a vag com to check for error codes?

Anyone??

Greg Roles
26-09-2008, 06:46 AM
OK, here's the info in the service bulletin about Active regeneration:

Lasts about 10 mins.
designed to heat the rear of the DPF up to 600-650 degrees.
The DPF has more platinum in the front over the back. The front runs hotter and this is where the passive, all day soot burn off occurs. When the colder rearward part blocks up, active regeneration occurs.

Exhaust gas recirculation is switched off to raise compustion temps
Extended injection of fuel occurs, with a secondary, smaller late injection to raise exhaust gas temps
Supply of intake air is adjusted with the electric "throttle" flap
Charge pressure is adapted (raised) so the driver feels no difference in power or driving


Also an interesting page on "over-run" operation in urban traffic.

In heavy traffic with strong changes in load, particular measures are required to maintain cleansing of the DPF. Normally no fuel is injected on over-run, but then the exhaust temps drop, and the DPF isn't regenerating.

If the car decides there is too much over-run happening:

A small amount of fuel is injected at over-run, approx 35 degrees after TDC
Since there is no main injection at TDC, there is no combustion and this extra fuel vaporises
This fuel then combusts in the DPF, and heat generated continues the regeneration cycle
The temp sender after the DPF controlls this process.

So it seems if you are a urban traffic driving rev head ( ie Mischa ) then the poor car will be doing this every time you back off the throttle at 4500rpms.

Perhaps this is why the lil wippersnapper had problems with his DPF early on.

I know I flog my car, but I stay between 2 and 4000 where the action is.:biggrin:

Russ59
26-09-2008, 07:39 AM
Thanks Everyone,

I haven't started the beast yet this morning but I have to take it into the VW service dept. in a couple of weeks to get a new plastic door mould fitted on the passengers front door (double sided tape has lifted) so as I said in my previous post, I have mentioned to the sales guy that I would have to get it checked so I'll have to wait and see what they say ( I hope it's not the usual spiel - "oh that's normal sir " !!) God help them if they do :brutal:. I may not be as lucky if it does it again and could end up being rear ended next time by some impatient wanker, I mean it's not like I ever hold anyone up in this thing !! They just have trouble keeping up !! Maybe that's what annoys them !!! :driver: :biggrin:

Russ

Guy_H
26-09-2008, 08:57 AM
Now you can image what a "tuning box" does to your DPF cycle :brutal:

Russ59
26-09-2008, 03:08 PM
Now you can image what a "tuning box" does to your DPF cycle :brutal:

Good or bad image ??

Russ59
26-09-2008, 03:15 PM
Took the car out for a short run today and everything appears to be fine again, car is running normally and idling at the usual 800 rpm once at operating temp. I will still get the VW service dept. to check it out and see if they can find any errors, don't want to experience that again in a hurry, especially in traffic !! :frown:

Russ

Guy_H
26-09-2008, 03:18 PM
Well a tuning "box" tricks the ECU into supplying more fuel & edits the feedback sent back to the ECU to say everything is normal, therefore on a DPF cycle, the system is trying to inject an "exact" quantity of fuel for the DPF burn, it gets an undesired extra amount of fuel. When I was last in Germany I was shown several burnt out DPF boxes that were the victims of over fuelling - not pretty & not cheap!

gerhard
26-09-2008, 03:19 PM
Took the car out for a short run today and everything appears to be fine again, car is running normally and idling at the usual 800 rpm once at operating temp. I will still get the VW service dept. to check it out and see if they can find any errors, don't want to experience that again in a hurry, especially in traffic !! :frown:

Russ

Good to see I was wrong, and your problem is not really a problem :)

Russ59
26-09-2008, 03:58 PM
Good to see I was wrong, and your problem is not really a problem :)

Cheers mate, yeah providing it doesn't do it too often I won't consider it a real problem either, but if it does it again under the same circumstances and someone runs up the back of me I won't be impressed at all. I think I might be doing a few nice day trips on a regular basis to keep the DPF flowing clean !!

Russ

Russ59
26-09-2008, 04:03 PM
Well a tuning "box" tricks the ECU into supplying more fuel & edits the feedback sent back to the ECU to say everything is normal, therefore on a DPF cycle, the system is trying to inject an "exact" quantity of fuel for the DPF burn, it gets an undesired extra amount of fuel. When I was last in Germany I was shown several burnt out DPF boxes that were the victims of over fuelling - not pretty & not cheap!

So are you talking about chipping (ie tuning box) causing problems with the actual DPF filter ?? Hence meaning it would be safer not to chip the vehicles fitted with the DPF ??

Russ

Greg Roles
26-09-2008, 06:21 PM
That's what the Guy man is saying. Makes sense to me, no way I'd risk a $40k plus vehicle with a tuning box over a properly integrated tune.

Thanks also Russ for being the DPF regen on cold guniea pig. Moral of the story is if you think the car is doing a regen cycle, drive it till it's done! If that happened to me cold, I'd pull over and let it idle for the 10 mins till it was back to normal!

Scary experience all the same russ!

Mischa
26-09-2008, 06:32 PM
i would never do any performance mods to my car with the dpf still in there. if anyone is serious about removing their dpf, pm me, i've found somewhere that can code for it.

DSGMAn
26-09-2008, 09:11 PM
So glad i don't have that cancer hanging off a downpipe on my turbo ^^

Black soot all the way for my 06 TDI - weeeeeee! :brutal:

But tuning boxes suck overall DPF or not.

Russ59
26-09-2008, 11:23 PM
Thanks also Russ for being the DPF regen on cold guniea pig. Moral of the story is if you think the car is doing a regen cycle, drive it till it's done! If that happened to me cold, I'd pull over and let it idle for the 10 mins till it was back to normal!

Scary experience all the same russ!

Hey Greg,
I just wish I'd known to expect this could happen, might be nice if VW warned people about the possibility and what may happen. Could be a real hazard in some situations !!! Fortunately all is OK and I will be prepared if it does it again !! :)

Greg Roles
27-09-2008, 08:41 AM
So glad i don't have that cancer hanging off a downpipe on my turbo ^^

Black soot all the way for my 06 TDI - weeeeeee! :brutal:

But tuning boxes suck overall DPF or not.

Sweeeeeet. When your kids show up at the Childrens with severe lung problems, I hope I'm there.

DSGMAn
27-09-2008, 03:08 PM
Sweeeeeet. When your kids show up at the Childrens with severe lung problems, I hope I'm there.

Damn - that's a nice thing to say.

Hope you're also lobbying trucking companies and everyone who drives petrol cars?

Don't hate the non DPF people - wasn't our choice.

Greg Roles
28-09-2008, 09:06 AM
Yeah sorry man, I rethought it and by then couldn't edit it, so I apologize being so harsh. I do see a lot of problems in my work, so I'm a bit sensitive I guess, especially what I see with the kids.

I know that there are plenty of bigger polluters out there, but I do find problem with people who laugh about producing a ton of soot. I had to breathe it in out cycling again this morning when the odd old truck went by, and it ain't pleasant. Sure it's my choice, but I look forward to newer, cleaner cars as technology advances. Even stock the DPF on the latest TDI certainly allows amazing power. My DPF will be staying very much put unless I can find a very clean burning tune, or use LPG or similar to clean it right up.

Anyway, back to the normal thread topic.....

DSGMAn
28-09-2008, 10:54 AM
Yeah sorry man, I rethought it and by then couldn't edit it, so I apologize being so harsh. I do see a lot of problems in my work, so I'm a bit sensitive I guess, especially what I see with the kids.

I know that there are plenty of bigger polluters out there, but I do find problem with people who laugh about producing a ton of soot. I had to breathe it in out cycling again this morning when the odd old truck went by, and it ain't pleasant. Sure it's my choice, but I look forward to newer, cleaner cars as technology advances. Even stock the DPF on the latest TDI certainly allows amazing power. My DPF will be staying very much put unless I can find a very clean burning tune, or use LPG or similar to clean it right up.

Anyway, back to the normal thread topic.....

I understand dude totally - I'm a cyclist myself.....I live in Pyrmont, inner city Sydney and walk/cycle to work everyday (Car is for weekends now). I personally can't wait for electric technology to take over and finally rid the world of at least car produced pollutants. The soot part of my write up was in jest....not much i can do about it until my bro hooks up some H2 Injection for me :)

Russ59
07-10-2008, 10:52 PM
Quick update on the DPF regen. cycle (cold engine) I had the car into the dealer today to fix the plastic moulding on the passengers door. I had mentioned to the Service Manager prior about the problem I had experienced with the car running like a dog and then dying on take off, they ran a diagnostics check on it and no errors were registered apparently so it must have been a " Cold Regen " If you suspect it's happening to you try and get off the road as soon as you can and let it complete the cycle itself because it's damn dangerous to try and drive the car once it's starts. :frown: On a brighter note the car hasn't missed a beat since then and when it was in today they did some sort of an update as well and the car seems to be running even better. :)

Russ

Greg Roles
08-10-2008, 07:09 PM
Hey Russ,

Good to hear. I actually owe you one, as when I pulled into my driveway last night I noticed it had started a regen cycle, idle was at 1000. I backed out and went for a drive for a bit, till it finished.

Funny it isn't mentioned in the manual, as it's a bit of a trap!

Russ59
09-10-2008, 01:45 PM
Hi Greg,

Car's running heaps better at the moment hopefully it will stay that way, I don't want to experience the "Cold Regen Cycle" again in a hurry especially in traffic ... what a nightmare. :frown: :duh: