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10854 Views 24 Replies 10 Participants Last post by  noobytoogy
Saturday night I took my wife's 2008 Touareg to work because she had just came home from errands and her vehcle was already warm. After an overnight shift I tried starting it and it would only half start and shook violently before quitting. I tried a few more times and same thing. It was cold this night here in northern Minnesota and got -13 degrees Farenheit. However, it has been outside in much colder temps and never had an issue. Long story short I had to get it towed and only to find out the exhaust was completely frozen up under the vehicle. According to my service department our era of Touareg does not have drain holes in the exhaust like the new generation Touareg and as a result it was just another one of the many problems we have had with this vehicle. The dealer ended up drilling some holes for us and even seemed in disbelief about the situation. And by the way it was not packed with snow underneath and I can assure you this vehicle is babied. This is the only vehicle I have ever had do this and I'm just annoyed at what has gone wrong on this thing considering the "premium" label. I told my wife the next issue and it is gone for an American SUV and we are done with VW.
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I know I'm splitting hair but after implementing emission control systems for "off-highway" equipment (excavators and container handling equipment at ports) last few years I wouldn't call it just as "catalytic converter" as on this size TDI's there is no "thing" that would do same stuff as catalytic converter does in gasoline car.

On gasoline engines, the emission control is through the catalytic converter (the internal honeycomb is made from platinum and palladium) that creates catalyst converting the hydrocarbons into carbon dioxide and water and also converts the nitrogen oxide back into nitrogen and oxygen.

On diesel depending the continents and engine cc's, the emission control can be either just SCR (selective catalytic reduction) or combination of DPF (diesel particulate filter) and SCR.

DPF and SCR requires ULSD diesel so these doesn't work on 3rd world countries with higher sulfur content..

Anyways, the DPF honeycomb traps the larger particles and the smaller particles are conveyed to SCR honeycomb together with DEF (diesel exhaust fluid here in States) / AdBlue (in Europe) to create chemical reaction resulting nitrogen and water vapor.

At some point the DPF becomes filled with particles and engine management will inject diesel fuel either directly (injector on front of DPF) or indirectly (cylinder injector spray timing while exhaust valve is still open) to burn off the soot and then convey those particles to SCR to process them as well.

The amount of water is far less than on gasoline engine with catalytic converter so I see no reason for weep hole.

Only time I see weep hole on SCR system is with vertical exhaust pointing upwards and the weep hole is used to drain the rain water that may rain in from vertical stack to prevent that amount entering to SCR, DPF and even to turbo. On horizontal lay-out there is no need for weep hole.

As gasoline car "catalytic converter" is more known to general public, by using just catalytic converter can easily create assumption those being same with gasoline and diesel while the detail of diesel requiring DEF as an catalyst to "ignite" the chemical reaction is left out of the context...

On the on-highway and off-highway equipment industry no one uses term catalytic converter and each is called with their own names , the DPF and the SCR.
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