MKV DPF dissection

Discussion in 'Mk5 VW Jetta, Sportwagen, and Audi A3 TDI forum' started by Greg Roles, Jun 29, 2011.

  1. Greg Roles

    Greg Roles New Member

    Joined:
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    Car:
    2008 VW GT TDI 170
    Hey all,

    I recently cut up a failed DPF that I got off a VWW forum member over here in Australia. I hope this provides some insight into the combined cat/DPF as fitted to the Euro PD170 TDI found in VW, Audi and Seat amongst others ( possibly Merc ).

    First is the very fibrous and weak insulative layer around the inside of the can, you can see it in the flap I cut off. As it's no doubt something along the lines of asbestos, I was wary of breathing it in! Secondly the innards of the DPF were a LOT cleaner than I thought. Seems the filter is made of full length cels that alternate at the very end being closed, and whilst the actual top was quite sooty, it was mainly full of the white ash you can see. This must be what builds up and can't be burnt back off.

    I actually got very little black on my hands which suprised me, but a ton of ash came out of it. Perhaps Ryan (ryder01) I got it off had it backflushed and baked or something, but I expected a lot more soot. The ceramic was incredibly strong, and laying into it with a hammer had little effect, I had to break it up with a big screwdriver and the hammer. Very much like pottery ceramic, made the same sound as it broke up, and cracked the same. Once I got a central section out, I was able to remove big chunks of the core which I will keep for future study.

    In all the medium was far more symmetrical and uniform that I was expecting, and the ash that fills it was a suprise being white.

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  2. Greg Roles

    Greg Roles New Member

    Joined:
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    Car:
    2008 VW GT TDI 170
  3. Greg Roles

    Greg Roles New Member

    Joined:
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    Car:
    2008 VW GT TDI 170
    Note the ash and symmetry in the design. Seems the filter is made up of several segments which are ceramically bonded together probably to give it extra strength against cracking.

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  4. Greg Roles

    Greg Roles New Member

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    Car:
    2008 VW GT TDI 170
    Here are the big chunks I have kept, clearly showing the layout. I could find no obvious "cat" portion, as VW states the platinum cat component is mainly at the front section of the DPF as it blocks from the rear over time.

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  5. chittychittybangbang

    chittychittybangbang Administrator

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  6. darrelld

    darrelld Member

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    Do you have any background on possible causes for the DPF failure?
  7. Greg Roles

    Greg Roles New Member

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    Car:
    2008 VW GT TDI 170
    Sorry for the long time between posts, not on here that much!

    Mate DPF's fail mainly due to non regenerable oil ash. This comes from your engine oil via the normal combustion process to a degree - thus important to use recommended low ash oils - but the main offender in my opinion is the PCV oil blowby system. EGR only increases that, as whilst lower combustion temps due to EGR assist NOX reduction, they also increase soot produced. This soot also eventually clogs the filter as no reaction ( regen ) is 100%.

    So for your DPF's sake fit a Provent or other high level oil catch can, and hobble your EGR as much as you can. This does up NOX emission though.

    Well my own DPF is rapidly reaching the end of it;s life, and I can currently only go about 100-150kms between regens now, the Vag Com soot level is about 35 grams, and a max of 40 grams is allowed according to VW. I am having trouble getting my experiemntal partial flow core out of China, so in the interim am going to simply cut open my own DPF cannister, pressure wash it out, and most importantly FLIP IT AROUND!

    Seems such a simple idea to me, given the core is basically a series of alternating "cups" and it is the inlet cups that are full of the white ash pictured above, in my mind flipping it should let that ash blow out the tailpipe to a degree, and whilst I'm not expecting another 120kms out of it, if it gives me another 30k plus I'll be happy.

    I will report on what I find, but it can only help prolong the usable lifespan in my mind.

    Oh yeah my DPF has failed early in my opinion, but I have been running a Viezu Race map for about a year now, and I know this is way beyond what they normally release to the public for DPF equipped cars, and it definately caused more frequent regens, but took the car from 6 cylinder power / traffic light derby spped, up to the v8's!

    Big, big fun : ):nana2:
  8. Greg Roles

    Greg Roles New Member

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    Car:
    2008 VW GT TDI 170
    The separate version above is only on the MK6 you now have in the USA. On the MKV like mine ( the Euro version ) there is indeed a cat, but it is all in one in the DPF core, and the precious metals are arranged so more is at the front, less in the rear, so as it ash fills it still acts as a catalytic converter. Seperation as per MK6 makes it cheaper to produce, and overall more efficient to meet Euro 6 emission laws. There is a "cat" in both versions!

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