MKV DPF dissection

[Greg Roles]

Finally started cutting up Ryans old clogged DPF today. VERY interesting..

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'm 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 cermaic was incredibly strong, and laying into it with a hammer had little effect, had to break it up with a big screwdriver and the hammer. Very much like 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.

[Greg Roles]

And the detail,

[Greg Roles]

Note the ash and symmetry in the design. Seems the filter is made up of several chambers which are ceramically bonded together probably to give it extra strength against cracking.

[Greg Roles]

Here's the big chunks showing the inner layout.

[Transporter]

Some good work there, Greg. I see the box is ready to be welded up, or not?

[kaanage]

Note the ash and symmetry in the design. Seems the filter is made up of several chambers which are ceramically bonded together probably to give it extra strength against cracking.

I'd say the "chambers" are standard base units used to construct the DPFs for varying sizes. It makes sense that the ash is white since the regen cycles should burn off the carbon. The poor thing much have been regenerating quite a lot near the end in a futile effort to clear the obstruction hence the relative lack of soot.

So there's no separate cat section at all?

[Greg Roles]

Some good work there, Greg. I see the box is ready to be welded up, or not?

Not by a long shot.....

I'd say the "chambers" are standard base units used to construct the DPFs for varying sizes. It makes sense that the ash is white since the regen cycles should burn off the carbon. The poor thing much have been regenerating quite a lot near the end in a futile effort to clear the obstruction hence the relative lack of soot.

So there's no separate cat section at all?

Nope, it all looked uniform, seems there must be some platinum in the front portion of the DPF, and less towards the back, but there was neither any silver, nor obvious sign of difference front to back, it must be integrated in the walls.

The new MK6 DPF has very obvious seperate pieces, but so too this is to keep the costs of replacing the DPF down, and makes for even lower emissions.

From the rear of the engine....

[noone]

JohnW provided a link to some VW tech manuals, this was in there...

http://www.volkspage.net/technik/ssp/ssp/SSP_336.pdf

Nice info Greg

[poyta]

No wonder you gain so much by removing it - it looks very restrictive.

[kaanage]

JohnW provided a link to some VW tech manuals, this was in there...

http://www.volkspage.net/technik/ssp/ssp/SSP_336.pdf

That's excellent - it clearly shows all the elements unique to the MkV GT diesel engine (at a basic level).
But the fact that VW moved away from the catalyst coated particulate filter so quickly shows the drawbacks of this since the DPFs must be clogging faster than their intended lifespan.

[gldgti]

that self study is a great read.

Greg - under "fuel quality" (right at the end) I would read that as good new for you. i.e - if you have a dpf delete, and no regen cycle happenning, then bio should be sweet.

Its great that it actually explains why rather than not. I always thought it was strange the way vw stopped saying bio was ok for their diesels right around the time the DPF's came in - before that it was just about encouraged!

anyway - as the self study mentions - the main DPF structure is made of silcon carbide coated with alumina (aluminium oxide) which is good for the platinum to bond to. the silicon carbide is a ceramic material very commonly used in these kind of applications.

You mentioned that there was a lack of black soot but a lot of ash - i would put forward a theory that the incorrect engine oil was being used - or - the oil was overfilled. This would lead to large amounts of oil vapour/ash being burned in the exhaust and subsequently clogging the DPF.

I have read one horror story from the states witha guy who bought a brand new jetta with a dpf. after just 10,000km the engine stopping at inconvenient times, because the DPF had become completely blocked. The reason - the dealer had used the wrong oil spec (he had a very early dpf car), AND had overfilled the oil at the first service. when i say the engine was failing - shutting down/refusing to restart due to fault codes.

there is an ongoing legal battle....

[jazd]

Self study is indeed a good read. Where can I get more?

I have NEVER had the active regeneration light come on in my car since I have owned it (6 months), I guess I do enough long distance driving (40km to work and back every week day) and give it enough stick!

[jazd]

In the event of failure from the temperature sender
before turbocharger, the turbocharger can no longer
be protected against excessively high temperatures.
Regeneration of the diesel particulate filter is stopped.
By means of the preglow control lamp, the driver is
informed that the vehicle should be driven to a
workshop. To reduce the carbon soot emissions,
exhaust gas recirculation is switched off.

Poor mans DPF removal? lol

[Greg Roles]

Self study is indeed a good read. Where can I get more?

I have NEVER had the active regeneration light come on in my car since I have owned it (6 months), I guess I do enough long distance driving (40km to work and back every week day) and give it enough stick!

Car does a no light active regen at 40-45% clogged, it doesn't let you know. At 60% (approx) you get the light, and it then tries like mad to force a regen, and wants you to drive at speed to get it hot. If that fails it goes on to put the car into limp mode at 75-80% clogged at which point you have to take it to VW to have it regenned with the bonnet open so it doesn't catch fire! The coli light comes on after the failed 60% regens, I've managed that already in my messing around.

[Greg Roles]

Poor mans DPF removal? lol

The above hapens eventually mate, the car will refuse to run after 80%. I've not been willing to confirm that though!