DPF wash out and rebuild

**Greg Roles** · 31-12-2012, 07:15 AM

Well my DPF had pretty much clogged at 120kms, and as I am still as yet to find the right sports core, I decided to recondition what I have to buy a bit more time.

The Viezu Race file no doubt led to an early fill level, and this is the reason most decent tuners won't put more than a "stage 1" or mid level performance tune on DPF equipped cars. My own DPF has gone from 3/4 filled ( 30g carbon ) which took 4 years, to the full 40g carbon in just a year of full on race files, so the soot / ash produced is too much for the general public. I was well aware of this going in though : )

Anyway my car was wanting to regen every other drive, and I only had about 50kms of range between regens, and this was driving me nuts. I decided to pull out the core and pressure wash it out, and see what happened.

Removal was relatively straight forward, and there is a great guide here, so I won't bother writing up that proceedure. Jazd did help me with a few points, so thanks for such a great guide!!

With the DPF out, it was time to cut it open with the aim of not damaging the core. As you can see from the pics below, it sits on a small ledge top and bottom, so I cut a little above the lower weld, so as to not damage this shelf, and also used a worn down 1mm cutting blade so as to limit my entry depth. You can see I still nicked the core in a few spots. The first pic is my prototype DPF and you can see I cut a bit too low. You can see the core is about 2mm below the case, wrapped in some sort of heat shield stuff, probably asbestos, so take care!! I used a mask just in case.

**Greg Roles** · 31-12-2012, 07:21 AM

The core would not pull out like that as it is a snug fit, so I had to open the case further.

This allowed me to remove the core, and the very delicate heat sheld, which despite your best efforts will likely fall apart. Mine broke into a few pieces by reassembly time, but I put them back in as best I could, this helps keep the heat in during regens, and you want this core to always be as hot as possible. Also very important to mark which side is the top or inlet, as you want to reverse flush the core. There are arrows on the side showing flow, but they are quite faint.

**Greg Roles** · 31-12-2012, 07:35 AM

Gurney time.

Well you can go to town with the pressure washer, I had mine right against the core on full power, and no physical damage at all, the core is quite strong. It is however like china and brittle, so if you drop it, you're going to be dealing with pieces! It must remain intact to allow the right pressure difference between the fore and aft pressure sensors, so I took great care not to drop mine!!

Here is what came out after a good 15-30mins of blasting up close, holding it with my foot. I got soaked as I sat down to get the water jet perfectly aligned with the long channels in the core. The non regenerable ash is white, and this is what I found the core I smashed up was full of. As you can see from the pics above, I had just finished a regen prior to cutting it open, and there is no black soot to be seen. The black stuff is not the problem!

An awful lot of what looked like sand came out, much more than I expected, and when you pick it up and rub it between your fingers it indeed feels like ash and rubs down to nothing. It is NOT any part of the physical Silicon Carbide core!

I washed away the removed ash, and repeated washes till I could get no more white ash out with the pressure washer.

I then spent a lot more time flushing it over and over in a bucket of water, and found the best method was to lower it in top last, and allow the entering water to "float" the channel contents out each time. This got a fair bit more out, and overall I spent a good two hours washing it out, figured I wanted it as clean as humanly possible. When I got down to very little coming out and the water staying clean, it was time to put it out in the sun, and tee up my brother for some Mig welding.

Putting it back together wasn't too tricky, but we had to wire it together to pull the can back together, as I already had a 1mm blade cut to fill, and the heatshield makes pulling that gap back down quite tricky. Still a few ales and we managed it, and home I went to bake "dinner". I figured an hour in the oven to drive off as much water as possible could only help, I didn't want the car freaking out from too much back pressure with an overly wet core. Probably not essential, just me being careful. A lot of water did indeed pour out the pipe, if I put a glass over the end it quickly showed condensation.

**Greg Roles** · 31-12-2012, 07:42 AM

I had intended to flip the core over, as I see no reason why this wouldn't work, and will expand on that later, but I managed to remove so much ash I figured I'd go for the maximum Cat effect. The Platinum Cat coating is integrated in the MKV core, and denser at the inlet and lessened towards the back, so flipping it would increase emissions as far as I can figure, but would allow any remaining ash to blow back out and basically give you a fresh core to fill. I will go into that on here later today.

So far so good, and I decided to reset the ash level back down to 5 grams to be safe ( 40 grams is full ) The car is running fine after a quiet test drive yesterday to blow all the water out of the core. Early days, I have a job up at Nambour this arvo, so if I make it, well I will label this process as a success.

Wish me luck!

**h100vw** · 31-12-2012, 08:36 AM

Good effort Greg. Could be a good halfway to a new core.

Gavin

**Umai Naa!!** · 31-12-2012, 09:14 AM

Top work as always.

I wonder if this is still considered as tampering? Could there be a legitimate market for this sort of thing?

**brad** · 31-12-2012, 10:14 AM

Greg
Why couldn't you leave the DPF intact & simply reverse flush with high volumes of water?

**Greg Roles** · 31-12-2012, 10:42 AM

Brad, that's the normal process you find workshops doing on YouTube, with people just blasting a gurney up the outlet, but you really would need immense pressure to clean out the very baked in ash in my opinion, and little came out of my core till I put the gurney nozzle right up to the surface of the core outlet and blasted away. To get the same effect would require some truly huge flowrates in reverse, possible, but not with anything I have. Perhaps the local firehose underneath a shopping centre?? Remember the inlet and outlet channels are not connected, and you are effectively trying to force water up the outlet, across the channel walls, and to then flush ash out of the adjacent inlet channel!

I had intended to flip it to be honest, as it is a symmetrical design apart from the Platinum, and that would allow any remaining ash to just blow out the tail pipe in operation, but it seemed to clean so bloody well I didn't bother. The DPF core I smashed up previously had very baked in ash, and it is compacted far more than you would think, years of pressure and regens will do that.

But sure a reverse flush intact would give you some effect, just not as much in my opinion, and given the removal process, you may as well do it properly. It takes some time to remove and install, although now i have done it once it would be a lot quicker second time around.

Umai, my whole business aim is to find replacement cores, sports cores, and to give people with clogged DPF aftermarket options, both stock and higher flow. Dealing with China is somewhat "difficult" though, hence me cleaning out my own core to get more time out of it.

Gav more driving today and the car is telling me that the core is at 0.0% loaded, so as far as the ECU is concerned this IS a new core. Will I get a further 120k out of it, who knows, but I will be monitoring it intensively, at least I am back to a happy car and all for a days labour.