Audi Q7, VW Touareg, VW PassatTDI DPF filter and Adblue FAQ page 2

Continued from page 1 with DPF pictures, DPF clogging, and active vs. passive regeneration

 For the 2.0L TDI non adblue engine, see the article specific to those engines in 1000q: 2.0L TDI engine non-adblue DPF FAQ.

How to check DPF soot loading

You can only view 3 groups at a time so once you're done there look at Group 104.  The number 3 spot is soot loading.  I believe the number 2 spot is calculated soot loading whereas 3 is measured.  I believe the number 4 spot is kilometers since the last regen.  There are no units or labels yet but I believe these labels to be correct.

Forcing an emergency active DPF regen cycle at up to 95% clogging or below 68 grams

Shown below is the procedure to manually force an emergency DPF regeneration.  The car will not do this on its own and you must manually start it.  This can clear out a DPF that is clogged up to 95% assuming that the blockage can be reduced to ash.  If it's too clogged from things like metals and not combustible particulates, it won't work.  The procedure is from ross tech, screenshots and notes are added here.

Before you begin, the ignition and engine must be on with the hood closed, transmission in park, and the parking brake on with no fault codes.  Look at engine measuring block 7, the second spot to check the engine oil temperature.  It must be above 70oC.  Check measuring block 104, spot 3.  It must be below 68 or else the filter will be damaged and could melt or catch fire.  As a good practice in general, don't park the car above combustible leaves, oil soaked rags, or the like.

Use VCDS to enter the engine module as shown earlier.  Click on "Coding II" and enter the security code 10016.  Use the measuring blocks shown above to monitor the engine.  The engine idle will raise to 1500 rpm and the regen could take up to 40 minutes.

Why you must use only 507.00 engine oil in your VW Touareg, VW Passat TDI, or Audi Q7 TDI engine

As mentioned earlier, particulates are reduced to a fine ash which gradually build up and clog the filter.  There's nothing you can do to prevent normal ash buildup but you can maximize filter life by only using VW 507.00 engine oil.  This is low ash oil.  The additives in other specification engine oils may produce more ash which will cause the filter to fill up faster.  A record of using this engine oil also makes sure the engine warranty can't be challenged if the dealer claims the problem is "because you didn't use the right oil".

The part number for 507.00 engine oil is VW# gvw 052 195 m2.  Some brands that meet this spec and some places you can buy it are: Castrol SLX Professional LL03, Motul specific VW 507.00, Total Quartz Ineo 5w30 507.00, and Mobil 1 ESP Formula 5W-30 (spec sheet linked).  If you wish to buy the oil from the dealership, 5w-30 507.00 part numbers are:
VW# g v52 195 a1 (gv52195a1) for .5 liter
VW# g vw 052 195 m2 (gvw052195 m2) for 1 liter
VW# g 052 195 m4 (gvw052195 m4)for 5 liters

It's also possible that there is something about 507.00 engine oil vs. others that is designed to deal with all the fuel that ends up in the oil from post combustion injection.  The post combustion injection is also known as an active regeneration "self clean" cycle.

Using biodiesel up to B100 with a VW Touareg TDI, VW Passat TDI, or Audi Q7 TDI

Diesel engines are completely compatible with biodiesel up to B100.  However, B100 may not be compatible with the emissions system.  Biodiesel has a distillation, flash, and boiling point higher than regular diesel which causes three potential issues when using biodiesel in a modern DPF equipped TDI engine.  For some basic information about biodiesel and VW, see 1000q: intro to biodiesel.

During an active DPF regen cycle, it doesn't vaporize as readily when injected without combustion.  This causes it to not be as effective at heating up the DPF which can require a longer cycle with more squirts of fuel to get the same effectiveness.  There's always some fuel that doesn't vaporize which ends up dripping into the engine oil in the crankcase.  Once there, it doesn't evaporate as readily and accumulates.  

The more biodiesel that accumulates, the greater the engine oil is diluted.  Regular diesel fumes are recycled into the air intake by the crankcase ventilation system and consumed by the engine.  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.

The other problem is trace metals or other contaminants from biodiesel processing.  These can build up and damage the catalysts or clog the DPF just like other contaminants.  Because comtaminants are trapped upstream, the Adblue NOx catalyst should not be affected.

One possible fix for biodiesel compatible with DPF equipped cars is simply to remove the DPF.  There are DPF bypass kits that will delete the DPF but I haven't seen any for VW or Audi because operation of the DPF and Adblue system is tied into the engine management.  You would have to make major changes to the engine computer to get it to ignore the fact or fool it into thinking that all those sensors and extra fuel injections were working normally.  Personally I would not tamper with the system not only because it's illegal on a federal level and probably most states, but also because it's in place to reduce emissions which harm everyone.

The best way to fix this problem is to add another fuel injector in the exhaust to spray fuel intended for the DPF instead of in the engine.  The reason it's not done is because of the much greater complexity and cost.  The first TDI in North America, the 1996 VW Passat used an extra fuel injector to reduce emissions but it really didn't work well and was disabled by adding a computer reflash and higher pressure fuel injectors to meet emissions.  See 1000q: VW Passat 5th injector for details. 

DPF technology is also getting better so that lower temperatures result in more effective burn off and less frequent active cycles.

The last step - NOx Selective Catalytic Reduction and Adblue FAQ

Diesels make more NOx because they run lean.  Smaller TDI engines don't use Adblue fluid because not enough NOx is created.  The larger 3.0L engines and the Passat use Adblue fluid and NOx catalyst to reduce NOx emissions.  It's furthest downstream to let the gasses cool down to around 170oC or 345oF.  Unlike the DPF, it's a pass through converter and not a blocked off filter.

The bsaic reaction with diesel exhaust fluid urea solution is: 4NO + 2(NH2)2CO + O2 → 4N2 + 4H2O + 2CO2. Some more reactions that occur are in the picture below. Selective Catalytic Reduction (SCR) breaks up NOx into Nitrogen and water in a NOx catalyst.  The DeNOx works at about 345oF and uses Adblue as a reduction agent instead of HC, CO, and H2 and EGR metering like the smaller engines.  It's delivered with a 5 bar (72 psi) electric pump to the metering nozzle where it is used in a ratio of about 1:20 of Adblue:fuel.  This ratio goes up or down depending on vehicle weight and engine load.  The chemical reaction is described below.  Before entering the SCR catalyst, the exhaust is sprayed with Adblue which breaks up into CO2 and ammonia.  The catalyst breaks the NOx and ammonia into nitrogen and water.  Reductions in NOx can be up to 80-90%.

Adblue fluid info and storage

Adblue is a brand name for diesel exhaust fluid (DEF) and is a solution of about 67.5% water and 32.5% urea.  I've heard the pee jokes already - you can't "stick it in the filler" to top off the Adblue!  Adblue fluid is an odorless solution of dissolved high purity urea crystals synthesized from ammonia and CO2 in water.  Urea is CO2(NH2)2, Ammonia is NH3.  Adblue is a weak base of about 9-10 pH (pH depends on solution concentration).

Adblue must be stored between -11oC and 55oC (12-131oF).  Optimum storage conditions are in a cool, well ventilated room (to avoid ammonia vapor buildup) between -5-30oC ( 23-86oF).  Below -11oC, the solution will separate into urea and ice crystals and increase in volume by 7% (all retail containers account for this expansion). The hotter 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.  The suggested fluid life is 2 years with a maximum freshness of 9 mo-1 year.  If you drive so little that the adblue in the car is 2 years old, use a vacuum pump to suck out the old fluid and replace with new fluid.

The Adblue tank on your car is heated when the car is running and the temperature is below -11oC.  It takes time for the exhaust catalyst to warm up to operating temperature so that gives the tank plenty of time to thaw out the fluid. Once the fluid is thawed it's unchanged and gets sprayed.  If the tank was heated when the car is off that would drain the battery when below -11oC.

Adblue interior spill cleanup like out of the carpet and safety information

If you get it on your skin, wash it off with soap and water.  If it gets in your eyes, rise with plenty of water.  In either case, consult a physician if irritation or ingestion occurs.  It is reactive with unalloyed or ungalvanized steel or copper alloys so store it in the plastic bottles they came in.  Only put it into the Adblue tank or dispose of it at a certified waste facility.  Do not mix it with chlorine or bleach since the ammonia that comes out of Adblue can create fatal chlorine gas.  If it's mixed with certain concentrated compounds it can also form an unstable explosive.

If you spill Adblue fluid in the car, wear rubber gloves and eye protection and soak it up with paper towels and water. Once it dries, it will form white urea crystals so keep it off the car interior. If it's already dried out into crystals, sweep up the crystals and dispose of them. Then use plenty of water and paper towels to clean up the remaining residue. If there's any urea remaining, it will form more crystals once it dries out. Disclaimer: Refer to the TOS Agreement for the full legal disclaimer.  Also refer to your materials safety data sheet (MSDS) for full safety information.  Adblue is not considered a hazardous material but dispose of it properly.

Adblue low tank warnings engine disable on VW Passat TDI, VW Touareg TDI, and Audi Q7 TDI

Since no adblue would result in non compliant emissions, the instrument cluster displays warnings until you refill once you trip the low level warning.  On the Touareg, it locks you out of all MFD (multifunction display) menus which means it only shows the adblue warning.  Once you run out of ad blue fluid the car will not restart after it's shut down (it will still run fine until you shut if off).  The first warning is at 1,500 miles and shows a yellow warning, the second warning is at 400 (Touareg) or 600 miles (Q7) and is red.  The final warning says that you cannot restart the engine once it's shut off so drive directly to a service station to add some diesel exhaust fluid.  If it runs dry you must add at least 1 gallon.  This is really no different than seeing the low fuel warning and needing to drive directly to a fuel station.

Where to buy Adblue at a cheap price

While you can buy it from any Volkswagen or Audi dealer, I suggest buying generic Adblue much cheaper at truck stops or online.  Dealer Adblue is a rip-off at $35-40/gallon vs. $6/gallon for generic fluid.  For example, a 2.5 gallon can is about $12 from autozone. The tank has sensors so that you can only add Adblue - don't put water in the tank because it will damage the system!  Some other brand names for adblue are blue sky, blue cat, Dureal, or Greenchem.  As of this writing, there are about 2200 retail locations which sell diesel exhaust fluid so you shouldn't have any problem finding it locally or at truck stops.

VW/Audi adblue part numbers

0.5 gallons # g 052 910 a2 (g052910a2)
2.5 gallons # gus 052 901 a3 (gus052901a3)
10 liters (2.64 gallons) # g 052 910 a4 (g052910a4)

How to refill the Adblue fluid in a VW Touareg TDI, VW Passat TDI, or Audi Q7 TDI

Below is a video showing some more Adblue info and how to add Adblue fluid on a VW Touareg TDI or VW Passat TDI and check the fluid level. On some non VW-Audi cars, they add a special additive to the fuel which breaks NOx into NO2 instead of injecting it into the exhaust.  It's not the same as your system so don't put Adblue in the diesel fuel. If you are adding Adblue due to a low level light, you must add at least 1 gallon and you must wait a little over 30 seconds after turning the ignition ON before starting the engine. Otherwise the light can stay on.

UPDATE TO VIDEO: If you don't want to cut a hole in the bottom of your DIY kruse funnel to refill it, you can also unscrew the top by turning it hard. There are plastic teeth to resist it but it's possible.


VW Touareg TDI

The -2010 Touareg has a 4.5 gallon (16.9 liters) Adblue tank which should last for up to 10,000 miles.  Scheduled maintenance to top it off is every 5,000 miles and during the 10,000 mile engine oil change.  The tank filler is under the spare tire.  Unscrew the cap holding the tire, lift it, pull the rubber cap off, and unscrew the Adblue tank cap.  Push the adblue bottle down to start the flow.  Adblue every 5,000 miles is included in the 3yr/36,000 mile free maintenance.  Don't let drops fall into the interior since it can stain the carpet and leave urea crystals.

The 2011 VW Touareg TDI was redesigned and uses a spare tire with much bigger spaces between the wheel spokes.  The Adblue fill port was also moved aft of the 2009-2010's opening.  It might be possible to reach through the wheel spokes to ad fluid without removing the spare. The capacity on this generation is 5.55 gallons (21 liters).

VW Passat TDI

The adblue fill port for the Passat is on the right side of the trunk (click to enlarge thumbnail). Pull the cover off, unscrew the cap, and follow the same instructions as the Touareg. VW's estimate of Adblue consumtion is 5 gallons/15,500 miles. Unlike the Touareg design, there's lots of carpeting around the fill port so it's important to use the spillproof adapters and not a funnel. There have been complaints of pools of fluid in the spare tire well and caked carpeting. Have the dealer fix this and make any necessary repairs caused by their damage.

Audi Q7 TDI

The Audi Q7 TDI has about a 6 gallon (23 liter) adblue tank capacity which should last over 10,000 miles.  The Q7 body is longer than the Touareg so it has 2 tanks: a 15.5 liter passive reservoir under the car and a 7 liter active tank next to the diesel fuel filler.  Here's an interesting cutaway of the Q7 system.  The adblue tanks are shown to the upper right.  The basic VW Touareg system is the same but because its body is slightly shorter, the single Adblue tank is under the spare tire.

The Adblue filler cap is removed with the spare tire lug wrench.  Below right is a .pdf pamphlet describing how to add it.  This adds fluid directly to the main active tank.  As you add fluid, the overflow drips down to the lower passive tank while air burps up through a breather line.  The dealer uses a special tool VAS6542 (VAS 6542) to quickly burp air out and fill the whole tank quickly, you can just add them by the bottle.  You can also use an old bottle as a funnel if you buy a big jug of fluid.  If you park uphill it will burp the air faster (thanks for the tip Dutch van Atlanta!)

Note: dealer prep only includes 2.5 gallons of Adblue in the tank.  The 5,000 mile service is included for free and includes topping off the adblue.  All service after that is your responsibility or included in the paid Audi care plan.  Adblue should be topped off at 15, 25, 35,000 miles, and every 10,000 miles after that.

Note:  Audi has a technical service bulletin TSB that says: "each time 6 liters or more of Adblue is added...an adaptation must be performed...an adaptation is required to ensure the sensors inside the active tank can correctly determine the Adblue fluid level".  This will incorrectly show the warnings even if you added fluid.  This was most likely due to older software versions.  If you keep the 23 liter tank above about a quarter tank full, the 1500 miles warning should never show up.  The newest software versions will acknowledge if you add fluid.  If the low fluid level light is on, adding fluid will turn the light on.  Here is someone from the Audi Q7 TDI forum whose low level light went away when they added fluid and never came back.

If you have more questions or comments about Adblue or why a DPF delete or DPF bypass is illegal, feel free to ask in the myturbodiesel.com forums