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I had the chance to use the ross tech VCDS to look at a 2009 JSW jetta sportwagen the other day and found the following info. I'll write this into a FAQ when I have the time and add the link here. If the pics disappear, refer to the FAQ.

Edit: please refer to the FAQ article for more details: http://www.myturbodiesel.com/1000q/DPF-Adblue-FAQ-VW-Audi.htm

The difference between the 2009 and 2010 4 cylinder TDIs and earlier ones is the complex EGR and exhaust treatment system. Every once in a while, the diesel particulate filter does an active regen cycle by injecting fuel after the main combustion, which heats up the DPF and burns up accumulated soot. This uses a little fuel and increases backpressure. To make up for it, the engine computer increases turbo boost slightly during this which will increase engine power and responsiveness. During sustained highway acceleration or other instances with high exhaust gas temperatures EGT, the DPF is under passive regen burning up soot because it's hot. This doesn't use any fuel because the engine isn't injecting any extra fuel.

Unlike earlier exhaust systems which had the gasses pass through a honeycomb-like filter, the DPF actually blocks the gasses to trap the soot. The filter has no spot where gasses flow through holes, gasses have to pass through the filter to go out the exhaust pipe. How clogged the filter is is one factor in how it determines when to do an active regen.

Symptoms of the car doing an active regen are hearing the extra radiator fan coming on and a burning rubbery odor by the exhaust. This can occur at stoplights or when you stop the car (while it's in the middle of a self clean cycle)

You can manually start a regen cycle using a VCDS. Go into adaptation, enter the security code 12233, and go for a highway drive. Change channel 18 from 0 to 1 and save. A yellow indicator light for the DPF will come on and the MFD mulfunction display will show a message.

Some things I noticed during an active DPF:

You will see soot load calculated, measured, and miles since last regen.

After a few minutes calculated and measured soot load went down.

After it was done, miles since last regen also went to zero.
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Discussion Starter #3
This is a diagnostic mode that would only be done by the dealer. The reason I posted this info is for information on some readings that are picked up by VCDS.

You would normally never need to think about regen and there is never any light that comes on, although I think they should have one just to let you know why the radiator fan is running fast for apparently no other reason.

On a side note, if anybody has a Touareg TDI or Audi Q7 TDI, I would be interested in scanning your car to monitor the adblue system.
 

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Great info; thank you!

Do you think the regen system will help prevent soot/EGR issues that have cropped up on earlier TDIs?

Also, I agree about having an indicator light to show when regen is happening. I'll bet it would prevent panic calls to the dealer and for those of us who care about how our cars work it would be "fun" to have.

-dan
 

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Discussion Starter #5
Do you think the regen system will help prevent soot/EGR issues that have cropped up on earlier TDIs?
Solve 1 problem, make 2 ? I don't know.

Also, I was cruising a Touareg forum, someone said the dealer was telling them to replace the DPF at 80,000 miles at a cost of $1,500. There is no specified replacement interval for the DPF and it can be cleaned. The problem is that according to what I've read, the front subframe has to be lowered to get access or for clearance. owner's manual just says to inspect the DPF every so often. If it were my car I would just drive it until the "Italian tune up" or manual regen initiation through VCDS wouldn't fix it.
 

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Interesting. When I was a Porsche-Audi tech, there were lots of procedures that in the workshop manual called for "drastic" stuff like subframe removal when it was not really necessary. Conversely, when it was useful to do (sometimes for repairs that did not specify it), it wasn't a huge deal and often could be partially dropped to make enough room without disconnecting everything in sight.

Very quick examples: We did Porsche 914 first gear syncros in about 20 minutes without breaking a sweat or removing the transmission or engine from the vehicle. We R&R'd Audi automatics much faster than the book specified by dropping various suspension pieces (and sort of subframe) and letting them hang after removing the entire exhaust system in one piece.

-dan
 
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