FYI: DPF regen info from my '09 TDI

Thanks for the pointer to the interesting reading, Varmint. Just thinking about this exhaust system makes my head hurt.

VarmintSlayer said:

Some interesting reading here.

http://www.chiptuners.org/forums/viewtopic.php?p=20440&sid=94ff7de418f345f43c53863d713454c5

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Awesome link and I think this points to what some people are referring to as a stutter or misfire. I think it's the NOx catalyst going into a regen cycle where the ASV and the exhaust valve are closing.

VarmintSlayer said:

Some interesting reading here.

http://www.chiptuners.org/forums/viewtopic.php?p=20440&sid=94ff7de418f345f43c53863d713454c5

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Note the key phrases:

• "Understanding this system without mentioning the ECU, the Sensors, all the Exhaust Catalysts, and some of the chemistry involved is impossible. Keep in mind each of these subjects has entire books written on it. "
• "so the driver never knows all this is going on"
• "(There are at least 27 sensors reporting to J623 - around 14 dealing with emissions.) "

Yikes ....

Turns out that info came from a TDI CLUB multiple personality member.

Humble Smoker is posting there now.

Or someone goofing around.

Maybe I missed it but does some sort of light go on in the gauge clusters that the car is currently doing an exhaust regen?

Nope....

I am trying to figure out if my car keeps attempting to do a regen. I drive mostly city miles and I am getting extremely poor mileage all the time.

Regen isn't your problem. You have only three fill-ups...economy will improve as your engine breaks in over the next 10K miles (see the graph in my sig). But with mostly city driving it will never be great...high thirties, forty tops, would be my guess. This is a highway car. Hybrids excel in the city (I'm sorry to say).

You'll get an idiot light if your DPF is getting too clogged. If so, just take it for a 20 min joy ride on the highway.

Missing Regen in my '09 JSW?

I had the same concern recently. I used to note the regen cooking, when I would stop in town or come into driveway, and jump out and catch the fans whirling. Popped the cover second time and felt around, yep, it was hot. And the smell by the exhaust pipe, slightly different. And quite warm. I could feel the heat being pushed from the fans to the rear under the body.

Then I quit hearing it for several months. I was getting concerned, but Tuesday had my free 10K maintenance at stealership and they checked their computer, said fine. Then, last night, as I drove into the driveway, it was just finishing as I opened my garage. I have been doing quite a bit more highway driving past month. My normal daily commute is 17 miles each way, up and down a mountain. So I am not concerned, but it is cool that you are doing all this poking around to understand regen...I learn from your experience.

So does anyone know how long a regen takes? Is it variable?

Turbine Suburban said:

So does anyone know how long a regen takes? Is it variable?

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I have read that when you turn off the engine the fans can "race" for up to 10 minutes. Therefore, I surmise that the re-gen takes about 10 minutes or less.

That said: I believe that some people here are confusing the fans racing condition with re-generation (they are related, but not the same). The car's computer orders a re-gen whenever it decides it needs it (for whatever reasons). Most re-gens occur while you are driving and you don't notice a thing (except perhaps a brief drop in instantaneous mileage, if you are REALLY paying attention). The *ONLY* time you hear the fans racing is when you happen to stop and turn off the engine while the re-gen process is still going on. Then the fans race to keep things cool under your hood. The DPF gets up to about 1200F (650C) while re-generating and they don't want any plastic bits to melt. Once the DPF (and DOC) get hot enough and fuel is added the collected soot ignites and that combustion cannot be stopped just because you turned off the engine.

Have Fun!

Don

Turbine Suburban said:

So does anyone know how long a regen takes? Is it variable?

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I'm not a mechanic by any stretch, but with nearly 40K on my 09 TDI, and based on a considerable amount of research along with real life experience, I'd offer these thoughts.

Regeneration happens in many forms. The BIG ONE... the one that really heats things up and takes several minutes to process appears (based on what I've read and experienced) to happen at or around 3,000 mile increments, and that ASSUMING you have a mixture of highway and city driving. I would suggest that if you do mostly slower stop and go driving it will happen more often.

But there are also other types of regeneration, two others of which I'm aware, and those happen much more often and are pretty much without notice. (again that's based on a couple of articles I've read). The only way I can tell those are happening is if I happen to be using cruise control on the highway. If I am, and I go down a mountain whereas only a very small amount of fuel is needed to maintain the speed, the car will tend to lock into a cycle of "on-off" lurching... sort of accelerate for 1 second followed by none, followed immediately by a one second acceleration followed by none... so that you could actually rock back and forth in the seat. This can be duplicated without using cruise by holding the accelerator only slightly on, but it's much easier with cruise on.

For a while I thought it was a cruise issue, but then read an article suggesting this happens during one of the frequent secondary regen cycles.

Hope that helps,

Wes

JSWTDI09 said:

The *ONLY* time you hear the fans racing is when you happen to stop and turn off the engine while the re-gen process is still going on. Then the fans race to keep things cool under your hood. The DPF gets up to about 1200F (650C) while re-generating and they don't want any plastic bits to melt. Once the DPF (and DOC) get hot enough and fuel is added the collected soot ignites and that combustion cannot be stopped just because you turned off the engine.
Don

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Actually I can tell if my car is regenerating by listening to the engine idling before I shut it off. Even before you shut off the engine, there is extra noise coming from under the hood and from what I can remember, some of it is from the fan.

No matter hot hot a DPF is, combustion always stop in the absence of oxygen. When an engine is shut off, there can be no source of oxygen and the regen cannot continue. Therefore it must cease burning and start cooling down.

My gut feeling is that the regen fans running with the engine off can't be a good thing. Be better to drive till it's over.

i have had 2 regens in my car since i've owned it. it has 3900 miles on it. first regen happened when i pulled into my garage and shut the car off, must of had my music louder than normal cuz i didn't hear the cooling fan screaming while i was driving. so fan was screaming and i could hear the burning cycle, exhaust makes a snap, crackle pop sound, and could smell the burn process at the tailpipe. it lasted about 7min after i shut car off.

next one, i definitely could tell it was regening. i was driving down a grade on the freeway and tach was fluttering between 2100-2200rpm and car was surging. this was very annoying. then i came to the place i was going, parked the car and the regen continued.

now i'm wondering if i should just drive it a little harder than i do now. i drive it pretty conservative, never really go above 2500rpm, maybe thats why it regens more often than most? what do you guys think?

Quick Storm said:

i have had 2 regens in my car since i've owned it. it has 3900 miles on it. [....] i drive it pretty conservative, never really go above 2500rpm, maybe thats why it regens more often than most? what do you guys think?

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I think you mean you've had two regens of which you're aware. That's different than having had only two.

Considering that regens happen every 300 miles, it is probably not the case that you're having more than most.

DoctorDawg said:

I think you mean you've had two regens of which you're aware. That's different than having had only two.

Considering that regens happen every 300 miles, it is probably not the case that you're having more than most.

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exactly dawg!, i went back into my training manual for the new bmw diesels, and found that the dpf regens are about every 3-500 miles the systems should be relatively the same. i forgot more than i learned for that training, oh well, thats why they have books.

it just seems funny to me that the regen was really noticable driving on the freeway on a dowhill grade with the cruise set at 68mph.

Beat a new diesel. Flog it and the cylinders will seal better. Diesels love work - don't baby it or it will never achieve it's power potential. Run it wide open up the steepest hills you can find. Remember its burning a lubricant and you have to run it hard to get proper cylinder wear and seal. The DPF cleans out better too like that.

But more often.

Any ideas about if I should keep driving the car when it's regenerating the DPF, to keep the temps down, or is it ok to park it and let the fans do their job? I just don't want to damage anything, it's not going to melt the DPF or Nox trap is it?

I doubt there's any damage done by shutting it down during a cycle, but if you know it is in the middle of one, I'd continue to drive around a bit.

I did not read all the post but on one of the most resent posts is 300 miles really how often the regen and how do you know it has or is in the regen mode?
I have all most 4k and have not noticed any regen going on.

Well i did some more reading it looks like it is 3k - 4k no indicators on the dash. If this is wrong that is fine just wanted to let you know I did go back.
Bill

BCNVC said:

I did not read all the post but on one of the most resent posts is 300 miles really how often the regen and how do you know it has or is in the regen mode?
I have all most 4k and have not noticed any regen going on.

Well i did some more reading it looks like it is 3k - 4k no indicators on the dash. If this is wrong that is fine just wanted to let you know I did go back.
Bill

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http://forums.tdiclub.com/showpost.p...1&postcount=42

I believe about 300 miles is the number.

The way I know that I've had regens (other than interupting a regen by shutting down the car) is by monitoring the MFD display. When I am driving, I generally have the instantaneous MPG displayed on the MFD and know what I should be seeing under certain conditions. My normal one way trips are between about 20-35 miles. So, when I see the instantaneous mpgs drops considerably from what I would expect to see and the average for that trip lower (by about 5%-10%) than I normally see, I feel fairly confident that a regen has ocurred.

VAG COM reports miles since last regen. Monitoring this number enables you to determine the ODO at which each regen occurs. For me, its about every 300 miles. I am guilty of having offered misinfo in post #1 in this thread when I said 2000 miles. I did go back and add a bold red disclaimer, but maybe I should go back and just delete my original post, or somethin. I've hesitated because I'm not sure whether a thread survives the deletion of its OP.

DoctorDawg said:

VAG COM reports miles since last regen. Monitoring this number enables you to determine the ODO at which each regen occurs. For me, its about every 300 miles. I am guilty of having offered misinfo in post #1 in this thread when I said 2000 miles. I did go back and add a bold red disclaimer, but maybe I should go back and just delete my original post, or somethin. I've hesitated because I'm not sure whether a thread survives the deletion of its OP.

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Hi, great info, I tried to monitor a regen today but the "miles since last regen" block is disabled on my VCDS. I just purchased the cable and I'm running their latest software. I believe it is address 108. All the fields are disabled and do not report a value.

cbauer4 said:

I think I have nailed down a possible "regen" indicator. Block 105,2 is currently called requested regens. I think it is really a DPF state indicator where:
0=Clean
1=Very Low Load
2=Low Load
3=Part Load
4=High Load
5=Very High Load(Regen Time)

I know the wording could be better but you get the idea. Everytime my car gets to level 5 the vehicle goes into regen within a couple seconds(confirmed by some other blocks). Can anyone confirm or dispute this? Its not an absolute regen predictor but my car always goes from level 4 to 5 in less than 50 miles(highway travel). I would like to hear from somebody if their car doesnt follow that schedule.

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I had taken the car in for a MIL light a few weeks ago and the dealer ran it for 80 miles to complete a regen, I got the car back with 90 miles or so on the trip odo.

This seems like what I observed today, I started this morning with 3 on the indicator on my way to work. with 280 miles on the trip odo. I drive about 8 miles to work all city no traffic, I'm pretty sure that it dropped to 2 at one point. On my way back home it started with a 3 again then half way if climbed to 4, 5 a few minutes later and immediately to 6. I notice that the temperature reported on the 3rd or 4th field climbed to 580C or so. Idle RPM was 900+. After 5 to 10 minutes the indicator dropped to 4 then 3. It might be 2 now but not sure. Temperature dropped to the 200 range. No noticeable drop in fuel economy. This is all city driving and I was in the 40mpg an stayed there thru the regen.

Just a few questions. which blocks are best used to monitor regens? I do not see values on the block reported by DoctorDawg. any ideas?
the way I see it my regen occurred under 300 miles, maybe 250. But this might have to do with driving pattern, I drive all city 40mph and usually at 1200rpm.

I also noticed the first field of address 105 has a binary number, I noticed that it started with something like 00000101 then 00001001 during the regen then back to 00000010 or so, don't know what this means

Update -- for those concerned that incidents of widespread DPF failures in '09s are imminent, here's a new factoid:

Way back in November 2008, when my car was still quite new (just a couple thousand miles on the clock)...see post #26 in this thread...I was investigating the secrets of the DPF with VCDS and routinely observed exhaust pressure differentials across the DPF in the range of 5-14 mbar (depending on miles since last regen). But then I got out of the VCDS game, mostly because my POS Windows laptop bricked and I decided to get a MacBook.

Anyway, last night I finally installed VMWare + Windows XP on my MacBook, so I can now run VCDS again. And of course the first thing I looked at today was the pressure differential across the DPF, under my standard measuring conditions (engine at full operating temperature, tranny in Park, engine revving at exactly 2000 RPMs). And I observed a pressure differential across the DPF of 10 mbar (at 105 miles since last regen, according to VCDS).

So, long story short: today, at 35,000 miles on the clock (about one third of the 120,000 mile "inspect DPF and replace if necessary" interval according to Bentley) my DPF is showing no more exhaust restriction than it was causing when the car was new. Conventional wisdom (to which I subscribe) holds that the DPF needs replacement when it accumulates substantial quantities of non-combustible ash and thus begins to overly restrict exhaust flow -- a condition which should be observable via VCDS as it develops by measurement of the pressure differential across the DPF. So just as my doctor assures me (with obvious amazement) that at the age of 58 I have the heart of a 20 year-old, I too assure my '09 TDI that at the age of 35,000 it has the DPF of a 1,000 mile-old. Cool beans!

My 2010 Jetta TDI has just under 4,000 mi. Had it at the VW dealer twice before anyone recognized it and told me that the fan running (after shutdown) and a bad smell was actually a regen in progress. (That makes me feel real warm and fuzzy about my dealer.) A trip from work to home is about 50 miles for me. Before arriving at the house, I go down a 30 degree or so grade hill for about three-quarters of a mile at about 60 mph, then through a flat area about one-half mile at about 35 mph, and finally a flat area about one-quarter mile at about 20-25 mph. Twice now, when I pull into the garage a regen has been occurring and I have turned the car off.

1) Should I leave the car running until the fan stops running?

2) Would the "coasting downhill" and subsequent low speeds trigger a
regen?

Needless to say, this regen stuff is new to me. I''m probably getting them on the road, as well, but the end of the trip deal has me curious.

sowegatdi said:

1) Should I leave the car running until the fan stops running?

2) Would the "coasting downhill" and subsequent low speeds trigger a
regen?

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Question #1 - It is not necessary to leave the car running. The only purpose for the fans running is to prevent the heat generated during a regen from melting any plastic bits under the hood. If the regen has not completed, it will just start again as soon as the exhaust temps get high enough the next time you drive. Not a big deal.

Question #2 - No. Regens can be triggered by several causes, such as pressure differences across the DPF, estimated "soot load", or just how many miles have been driven since the last regen. Coasting and slow speed driving will not "cause" a regen. That said: Exhaust gas temperature has a lot to do with whether a regen will happen. As long as you do some highway driving (rpms at around 2000 or more), regens are not a problem. The only regen "problems" I have heard of are from people who only do short trip city driving. This does not allow EGT to get high enough for a regen to start. As for coasting in gear - this does not hurt anything because when your foot is off of the accelerator pedal and you are coasting the engine burns no fuel. No fuel equals no soot, therefore no clogging of the DPF. This is also an excellent way to improve your average mileage (no fuel burned).

Have Fun!

Don

JSWTDI09 said:

If the regen has not completed, it will just start again as soon as the exhaust temps get high enough the next time you drive.

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One minor correction to a very good post:

Due to weather and driving conditions this winter I have now had four (4) interrupted regens in a row. In none of these cases has a regen started again the next time I fired up the car (despite the fact that the next start-up was always a highway drive, with EGTs and revs that would otherwise have permitted a regen)...rather, in every case the ECU simply waited the standard 300 miles to initiate the next regen (I know this for sure because I'm collecting DPF data daily in preparation for a new thread on this topic...coming soon). I won't say that it would never be the case that the ECU wouldn't re-initiate a regen after the next start...maybe if some parameter such as DPF pressure differential or carbon load was way too high this might happen. But, based on my experience, it is not usually the case that an interrupted regen will be followed by another attempt when you next start the car.

I'm no expert, but I would guess that whether a regen restarts when you start again would depend on how successful the interrupted regen was (in other words whether it was just beginning or whether it was nearly finished). I am assuming that if the ECU has reason to believe a regen is still needed, it will try again whenever possible. Of course, if it decides that it is not needed (the last regen was successful enough), it would not bother.

BTW: Thanks for all of your research about regens. I eagerly await your next thread with even more information.

Don