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DPF filter system overview and Adblue FAQ

15714 Views 14 Replies 10 Participants Last post by  chittychittybangbang

This FAQ article describes how the DPF and Adblue system works, discusses potential problems like filter clogging, how to manually activate an active regeneration cycle, and other FAQ. It was written for TDI but the basic description of the DPF can also apply to BMW 335d, BMW X5 xDrive35d, Mercedes Benz GL, ML 320 or 350 BlueTec, E320 Bluetec, or any diesel car that has DPF or Adblue. There were some other makes like Peugeot that used a fuel additive for NOx control but none of the cars in the US Canada use this system.

Pre clean diesels only had an oxidation catalytic converter for emissions. The V10 Touareg TDI had DPF (except for 2004) but no Adblue. Ultra low sulfur diesel ULSD was the key in the clean diesels - older fuels can clog the exhaust filters. Because the reduction in sulfur is 97%, it gives you an idea of how dramatic the change was. All new Audi TDI and VW TDI have DPF. Larger engines or heavier cars also use Adblue fluid sprayed into the exhaust to cut NOx emissions by up to 80%.

Since the article is pretty long, here's how it's organized:

There are 2 basic types of clean diesel exhaust systems on TDI. Those with adblue (2009+ VW Touareg TDI and Audi Q7 TDI) and those without (2006-2008 Touareg TDI and all other 2009+ TDI). The larger and heavier cars with V6 engines need adblue to meet emissions.

All modern clean diesels have 3 major emissions components: an oxidation catalytic converter, a DPF, and NOX catalyst (with or without Adblue). Each of these are described in detail in the FAQ article linked above. There are also numerous O2, temperature, and backpressure sensors. Because of these sensors, there is currently no way to delete the DPF or do a DPF bypass without a rewrite of the engine management computer.

Some interesting facts about Adblue fluid that I learned while writing the article: Adblue must be stored between -11oC and 55oC (12-131oF). Optimum storage conditions are in a cool, well ventilated room between -5-30oC ( 23-86oF). Below -11oC, the solution will separate into urea and ice crystals. This is why the storage tank is heated at -11oC. The more you go above 30oC, the more the ammonia will come out and while it's still considered usable, its lifespan is slightly shortened. Above 55oC, a noticeable amount of ammonia will be released and the solution can become unusable.

VW/Audi adblue part numbers
.5 gallons # g 052 910 a2 (g052910a2)
2.5 gallons # gus 052 901 a3 (gus052901a3)
10 liters (2.64 gallons) # g 052 910 a4 (g052910a4)

click the FAQ article linked above or here: http://www.myturbodiesel.com/1000q/DPF-Adblue-FAQ-VW-Audi.htm for pictures, videos, and more detail.
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It's a lot more complicated than I thought. Who said diesels were simple?
They haven't been simple since turbos, DBW, and DI.
Interesting...maybe in a few years you could see that part equipped since it would pretty much greatly reduce the active DPF regenerations. As mentioned in the FAQ article, the whole point of active regens is to clean out the particulates that aren't burned off during passive regenerations of the DPF from normal EGT temperatures.
I'm guessing that since they didn't invent it they'd have to license it though. The way the auto industry is going I don't think they're keen on that.

hi guys, new on this site, from SA, world cup country. can anyone help with user manual for supervag, or a site where i can download, cheers
Added some great pics thanks to hobojoker and mike. This is the rest of the exhaust system.

Here is a picture that was already in the writeup: this is the DPF filter. You can't see it without removing it or lowering the front subframe. Because of access, it looks like it'll be a real PITA to remove.

I have confirmed that the CJAA engines (all 2010+ models except Audi A3 TDI) have the 2 piece DPF filters/NOx catalysts. The CBEA (2009 VW TDI and 2010 Audi A3 TDI) engines may have 1 piece assemblies which are definitely harder to handle and remove.

The entire exhaust system is v-band clamps so they are easy as pie to remove.

closeup of the exhaust valve
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Nice pictures. I'm surprised at all the plastic. It must be for aerodynamics or rust prevention.
Maybe sound too? I'd think salt would get trapped above the plastic instead of getting washed out but that's what's undercoating is there for.
Maybe sound too? I'd think salt would get trapped above the plastic instead of getting washed out but that's what's undercoating is there for.
That's why you pay the extra $1 for the ultimate wash with the underbody spray.
Added a small section about DPF equipped VW TDI and Audi TDI and how biodiesel affects it. The excerpt below.

The newer common rail TDI engines (CRD) in VW Jetta TDI or other models with DPF will run as well on biodiesel as older TDI engines ran fine on biodiesel. However, using biodiesel has three main problems. During the post injection combustion, it can collect in the cylinder instead of vaporizing and raising the EGT to heat up the DPF, preventing normal active DPF regenerations. By not vaporizing, biodiesel works its way into the engine oil much more than diesel. Because biodiesel has a higher distillation and boiling point, once it's in the oil, it accumulates and dilutes the engine oil.

There's always greater engine oil dilution during a post combustion injection cycle but regular diesel can evaporate more easily than biodiesel out of the engine oil. Once it evaporates, it's recycled into the air intake by the crankcase ventilation system and consumed by the engine. Biodiesel accumulates because it doesn't evaporate as easily. At a 2008 biodiesel conference, a VW representative said the engine could tolerate up to 50% fuel mix in the oil but no more. (source) This level could be exceeded after 10,000 miles with just B5. B10 would definitely exceed this level.

Some possible solutions are to delete the DPF on your VW or Audi TDI or install a DPF bypass kit. The engine tuning must also be adjusted to account for the removal of post combustion injection of fuel and DPF removal. It might be possible to tune the post combustion injection to have bio produce the same results as regular diesel.

The future of DPF systems might substitute an extra injector in the exhaust to inject the post combustion fuel downstream of the engine instead of right in the engine cylinder. This type of system is required if the DPF is downstream of the Adblue or NOx catalyst. Modern systems which don't use post combustion injection at the engine use this type of injection. In fact, when TDI was first introduced to North America, the VW Passat TDI used a low pressure injector in the exhaust to burn up fuel in the catalyst. It was discontinued because it didn't work very well, see 1000q: VW Passat 5th injector for details. Technology has improved since 1994-1995 so it's possible this type of system might return. The main obstacle is additional complexity and cost vs. an extra squirt at the existing fuel injectors.
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:( I was planning on trying some B20. From what I can gather, you can just change the engine oil more right? Does anyone do a DPF delete tune yet?
The article was already over 11 pages of text not counting the pictures and videos so I had to split it up. There's now a page 1 and page 2.

The Touareg TDI and Audi Q7 info has also been split into its own FAQ article for systems that use Adblue fluid. This way you don't have to read about stuff that doesn't apply to your car and it shortens the article.

Another pics added to the FAQ, many thanks to the guy who took it, his contact info is in the picture. This shows the difference between the early 1 piece DPF-NOx and the later 2 piece DPF-NOx assembly. He let me know that you CAN remove the DPF without lowering the subframe for clearance (factory method). You can instead remove the passenger side axle and the center subframe section for clearance which is much easier and won't affect the wheel alignment or require an engine support.

He also gave me a heads up about VW.uk's page here: http://www.volkswagen.co.uk/new/golf-gti-vi/which-model/engines/emissions which compares the co2 emissions of a few Golf models. As you can see, the Golf 170 hp TDI has significantly lower CO2 than their 210hp (GTI) or 270 (Golf-R) gas engine, for the manual trans, 21% less and 32% respectively. All meet Euro 5 emissions regs.

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