FYI: DPF regen info from my '09 TDI

JSWTDI09 said:

I eagerly await your next thread with even more information.

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Here ya go, Pilgrim: Long-term DPF data project

Whoa!! You guys are waaaaay ahead of me on this. I was getting concerned because we had had two or three regens that just happened to be occurring when the vehicle was being pulled into the garage. So, you're telling me that if the car is driven close to 100 miles per day, and a regen occurs when the vehicle is put into the garage, there is a good chance that on the third day after that, another regen will occur in the garage. So don't worry about it, huh?

sowegatdi said:

Whoa!! You guys are waaaaay ahead of me on this. I was getting concerned because we had had two or three regens that just happened to be occurring when the vehicle was being pulled into the garage. So, you're telling me that if the car is driven close to 100 miles per day, and a regen occurs when the vehicle is put into the garage, there is a good chance that on the third day after that, another regen will occur in the garage. So don't worry about it, huh?

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I don't think that the regen occurs at 300 miles exactly. More likely that it might start somewhere in those 100 miles and you won't even notice it.

I have a different story, My commute is about 8.5 miles each way every day.
I only remember interrupting a regen once when I got home one night, yet I got a MIL light. I didn't have a VAGCOM then so I can't confirm the dealer's findings, but they drove my car on the highway for 80 miles to solve the issue (A mechanic took it home that nigh or something)

I do remember that I used to stop along the way home a few times every now and then, grocery store, etc. I have since learned to avoid stopping along the way, or only when absolutely necessary. I try to do the 8 miles in one drive and hope the regen occurs before I get home.

As per doctor I most not be doing ANY passive regen, since I'm always on the 1K to 2K range when accelerating and cruise at 1200rpm. I do take it to 3K once or twice during the drive to exercise the turbo vein but that's about it.

sowegatdi said:

Whoa!! You guys are waaaaay ahead of me on this. I was getting concerned because we had had two or three regens that just happened to be occurring when the vehicle was being pulled into the garage. So, you're telling me that if the car is driven close to 100 miles per day, and a regen occurs when the vehicle is put into the garage, there is a good chance that on the third day after that, another regen will occur in the garage. So don't worry about it, huh?

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Well, I would definitely say "don't worry about it". If yer DPF light doesn't come on, yer golden (and if it does, you just need to go for a 15 minute highway drive). As to the specific scenario you pose, I really wouldn't hazard a guess. Too many factors. Trust the ECU to do the right thing, and don't let a few interrupted regens freak you out.

One thing I am sure of is that it is not the case that "...another regen will occur in the garage." Ya gotta be driving (over 37 MPH, with EGT above some unknown-to-me value) to allow a regen start.

Have not seen this mentioned yet in this thread...
Has anyone used the "ScanGauge" to monitor Differential pressure or other to indicate an active or imminent Regen?

Does anyone know what parameters are needed to program the scangauge to read any of this?

Dagw00d said:

Have not seen this mentioned yet in this thread...
Has anyone used the "ScanGauge" to monitor Differential pressure or other to indicate an active or imminent Regen?

Does anyone know what parameters are needed to program the scangauge to read any of this?

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I don't know about ScanGauge, but it is possible with Vag-Com (VCDS). Read this thread:

http://forums.tdiclub.com/showthread.php?t=273171

Have Fun!

Don

Scangauge / Temp / Instantaneous MPG

I found a way of telling if your car is in a Re-Gen!

- Your Engine temp goes up to around 205F
- Your Instantaneous MPG goes up about 5MPG's.

Idle rpm also increases by about 150rpm.

Yes, idle goes up, but you can't detect that at highway speeds.

Dieselfitter said:

Yes, idle goes up, but you can't detect that at highway speeds.

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Unless you have a manual transmission.

Not to start another "Is the DSG an Auto or Manual tranny?" rant, but what would make a difference between 6th gear in a manual vs. 6th gear in the DSG, or any other gears for that matter, in regard to feeling a regen while motoring? Just curious is all since I've never actually noticed a regen at speed, but only when slowing down or stopped, and then only by hearing the fans running.

How would having a manual trans help me to know I am having a regen while driving?

pleopard said:

Idle rpm also increases by about 150rpm.

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I've never noticed that. I've never noticed the ECU increasing rpm for any additional load like a/c, fans, etc. Why would idle rpm need to increase during a regen?

Dieselfitter said:

I found a way of telling if your car is in a Re-Gen!

- Your Engine temp goes up to around 205F
- Your Instantaneous MPG goes up about 5MPG's.

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Why would instantaneous MPG go up??? Your using more fuel during an active regen not less.

What I notice during a regen is that the instantaneous fuel mileage on the MFD decreases significantly. When cruising at a constant speed, I continually flip between instantaneous and average MPG. During a regen the instantaneous drops about 5 - 7 MPG from what I would normally expect.

Plus 3 Golfer said:

I've never noticed that. I've never noticed the ECU increasing rpm for any additional load like a/c, fans, etc. Why would idle rpm need to increase during a regen?

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As I understand it, the idle rpm goes up during a regen to increase exhaust gas temperature. EGT must be high enough to get the regen process started (and perhaps to keep it going). Therefore increasing the idle and perhaps closing the exhaust flap is all about raising the EGT to the required level.

As for your thoughts on mileage - I agree completely. It goes down, not up.

Have Fun!

Don

JSWTDI09 said:

As I understand it, the idle rpm goes up during a regen to increase exhaust gas temperature. EGT must be high enough to get the regen process started (and perhaps to keep it going). Therefore increasing the idle and perhaps closing the exhaust flap is all about raising the EGT to the required level.

As for your thoughts on mileage - I agree completely. It goes down, not up.

Have Fun!

Don

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I don't know it to be 100% fact, but I believe the exhaust flap is for EGR purposes and does not affect the regen process.

Pelican18TQA4 said:

I don't know it to be 100% fact, but I believe the exhaust flap is for EGR purposes and does not affect the regen process.

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You could quite easily be correct. That's why I included the word "perhaps". I am certainly no expert on these things. I do, however, believe that the increased idle speed is to raise EGTs for regen.

Don

Closing the exhaust flap is to increase exhaust temperature and to increase oxygen (see 2 below). There is nothing mentioned about increase idle speed to increase temperature. When you think about it, 150 rpm idle increase means little to higher temps. And I've never seen an increase in idle rpm during an active regen.

ECM J623 has five ways to increase the exhaust gas temperature for active regeneration.
1. Regulate intake air – MAP sensor regulates Throttle Valve Control Module and Exhaust Valve Control Module to increase/decrease free air and stoichiometric control.

2. Shut off EGR to increase combustion temperature and increase free oxygen in combustion chamber.

3. Delay Main Injection and initiate early Secondary Injection.

4. Initiate late Secondary Injection to create Hydrocarbon vapor in cylinder and push to exhaust.
(Injection Quantity Calculated by EGT sensor signal from between DOC and DPF.)

5. Hydrocarbons are ignited in the DOC raising EGT to degrees 650 C in the DPF.

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I could have sworn I saw on my scan gauge using x-gauge mode a reading of 1.2PSI of boost at idle during my last REGEN.
I usually see practically 0 at normal idle.
Anyone else noticed boost levels at idle like this?

Diesel Fuel said:

I could have sworn I saw on my scan gauge using x-gauge mode a reading of 1.2PSI of boost at idle during my last REGEN.
I usually see practically 0 at normal idle.
Anyone else noticed boost levels at idle like this?

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Yup, even my analog boost gauge shows about 1 psi of boost at idle during an active regen.

What I meant to say is; The scan gauge 'shows' an increase of 5mpg, but the car is not getting 5 mpg increase.

A funny quirk with scangauge/ecu , when on regen?

Diesel Fuel said:

I could have sworn I saw on my scan gauge using x-gauge mode a reading of 1.2PSI of boost at idle during my last REGEN.
I usually see practically 0 at normal idle.
Anyone else noticed boost levels at idle like this?

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I'm certainly not an expert in regeneration (nor much else) but I would expect boost to go up because air is needed not only for normal combustion but also for for active DPF regeneration (point 1 above in the quote on regulating air).

But I don't know why rpm would necessarily be increased. For example, at 2000 rpm I would expect more boost during active regen than normal because additional air is needed for the regen process over and above the air needed for turning the engine at 2000 rpm. Rpm is still at 2000. It doesn't increase. I would think the same principle would apply at idle. Next time I notice an active regen, I will certainly look at rpm when stopped to see if it is higher than normal.

I've always wondered what temps are required at the DPF to support regen? ie that temps do the heads/valves see? Or do the new Common Rail Motors have a 5th injector in the exhaust?

I'm concerned what all that extra heat maybe doing to the longevity of the top end of the motor and more importantly the turbo.

Westro said:

I've always wondered what temps are required at the DPF to support regen? ie that temps do the heads/valves see? Or do the new Common Rail Motors have a 5th injector in the exhaust?

I'm concerned what all that extra heat maybe doing to the longevity of the top end of the motor and more importantly the turbo.

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Passive regen requires 300 to 450C. Active regen temps are 550C to 650C. CR TDIs use secondary injection after the main injection to raise temps in the DPF. Here's a link to read.

I assume that the heads are still cast iron like my 1.9L as Aluminum melts at about 660.4C.

There have never been any Volkswagen cylinder head made for passenger car engines made from cast iron. All are made from aluminum alloy.

... and just because the gas temperature inside the engine or exhaust port is 600 C or whatever, doesn't mean the surface temperature of the aluminum (which is in direct contact with the cooling jacket water) will be even remotely close to that.

VW diesel engines and for that matter, countless gasoline engines use aluminum pistons and aluminum heads, even though combustion conditions always go far above the melting temperature - but only for a fraction of the time. Heat transfer between gases and a solid surface is not fast enough, compared to the VERY fast heat transfer through the aluminum itself, to melt the aluminum. Unless, of course, you either get the tuning wrong, or run the engine out of coolant or oil ...

And aluminum develops an oxide layer that melts in the 1900C range that is alot less thermaly conductive than aluminum (about 1/10 of aluminum). What heat makes it through the oxide layer is easily sinked away by the rest of the aluminum. I have played with welding aluminum, the oxide layer is tricky.

And that 650 *C is in the DPF itself, where the extra fuel squirt is getting burned to generate that temperature. The DPF is in the engine compartment but it is definitely south of the engine block.

DoctorDawg said:

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.

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Hi Doc,

Last Saturday I did a 2 mile drive first thing in the morning, 8:30 or so, Temperature must have been 78 or something. Took me 10 to 15 minutes to get there and I noticed when I was parking that the fans were on. Oh crap, a regen NOW! I thought, and it came like 40 miles early. Oh well had no choice but to turn it off. Fans did not remain on cooling the car. must have been on the early stages. 3 hours later I get back on the car and drive 2 miles back home. Notice the fans going and rpm on the 900s.

Didn't want to risk it and took a 50mph road I have near home for about 5 miles did a U-turn and drove back, Got home and idle speed and fans seemed normal so I parked. Today I confirmed I had a regen 18 miles ago, which seems about right since I drove 18 miles today. for the first time since Saturday.

I guess in this case regen restarted. This is the second regen on a row were I had to alter my plans around the regen. Last time I drove 2-3 miles to my favorite gas station first thing that day, Had 2 gallons left on the tank. but as I'm getting there I noticed a regen going. I continued on with the rest of my commute and refueled at the end of the day. This last one I had to take a scenic detour. Oh well. better this that another Check engine light,

My regens seem to be starting very soon after the car starts from cold. within 2 to 3 miles. I guess that is good because my work commute is only 8 miles.

Pressure across DPF was about 15 at 2K rpm

TDIMeister said:

There have never been any Volkswagen cylinder head made for passenger car engines made from cast iron. All are made from aluminum alloy.

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I imagine that even if the block is aluminum it would have cylinder sleeves from a harder metal. Aluminum is too soft to handle the constant friction of the rings.