Audi A8L TDI (D4) delete downpipe, firewall, "Plenum Chamber Bulkhead"

[Digital4n6]

I'm stuck on the struggle bus. Trying to remove stock downpipe from my 2015 Audi A8L (D4) TDI and even had to cut off one of the downpipe studs. Now that everything is loose, can't seem to get enough clearance to remove the darn thing. Is there a method to remove the firewall section? Removed the nuts pictured, there was no fuse holder, and even all of the nuts that hold the shiny heat shield onto the black metal "Plenum Chamber Bulkhead".

 

[oilhammer]

They are usually stuck in there, the rubber seal melts a little and glues them in place. Some models also have a strut brace that has to come off, that will in turn usually have other things attached to it. It's a process. Often the engine harness has to be removed from the ECU and other attachments in the pass-through in the cowl chamber to let the firewall piece come out, too.

 

[Digital4n6]

Thanks, I tried to remove the strut brace but the two wiring harnesses are still connected. It's loose, so shouldn't be interfering. I did see a computer module mounted just underneath the strut brace with two (visible) nuts that may be attached to the black metal plenum bulkhead. That's my next step, but the front part isn't even wiggling.

 

[oilhammer]

I'm usually dropping the engine out, so I have that all loose anyway. I've never tried to just R&R the DPF with it in the car. The newer longitudinal car engine/trans mounting arrangement is exceedingly complex, LOTS of bolts and brackets at all different angles. I just did a low pressure power steering hose assembly on a V8 A8L, and that was a royal pain.

 

[Digital4n6]

The ECU had two 10mm nuts and the two plastic expansion bolts (#7 in diagram, one each side) were hidden under the insulation mat.

 

[oilhammer]

Yeah, I figured the ECU was involved somewhere. They vary on what all is connected and how things are arranged model to model and with whatever equipment they have.

 

[Mcdmarkd]

Any progress here? I am at the same stuck spot and wasn't sure what parts I have to remove to get the dpf out. Only had the parts for 2.5 years.

Thank You

 

[Digital4n6]

Yes, had to remove the firewall thing. It was a serious pain in the taint.

The nut on the underside of the downpipe attached to the turbo is too difficult to remove without taking out the firewall. Once you do that, much easier since you'll have room for a wrench. PB Blaster soak for at least a day is definitely your friend.

One of the 3 downpipe to exhaust wouldn't come off (130k miles) and I couldn't get a grip with a bolt off socket, so I ended up spending way too much time carefully cutting/grinding it off with a dremel metal cutting wheel attached to a dremel flexible extension. Had to use electrical tape to a piece of rebar to make a stable handle for the flexible dremel extension thing.

Underneath, having the lift made a huge difference. The one nut accessed from the underside for that exhaust part came off rather easily. I loosened the slip fitting near the car's midpoint so as not to have to replace the gasket after the second cat. In hindsight, didn't need to mess with any of that.

Post pics of your progress or questions and I'll help out if you run into any issues.

MPG after the stage 2 tune and downpipe was 39 mpg with a steady foot, but man, the difference in quick acceleration on the highway is incredibly noticeable!

 

[oilhammer]

A tuned/deleted V6 TDI is certainly a force to be reckoned with. And that's from a guy who has been able to experience crazy fast cars like the new RS7 (which'll beat a Hellcat Challenger off the line, to 60 by a half second, and never stop pulling away right up to its 200+ MPH top speed).

The smooth thrust the diesels make is astounding, and getting better fuel economy than any Camry can at those speeds is a nice bonus.

 

[Mcdmarkd]

Thank You

Have lift

Have all the dpf bolts off and is loose except the lowest sensor. and the metal to rubber line

Have the cowl propped up and most of the shield bolts loose.

Didnt know if the strut brace needed to be loosened of just the shield. Just decided to stop before I went too far or did something stupid.

Yeah, I have had a stage 2 malone tune for 2 years. My car was using 2 quarts per oil change when I got it 90000 miles to maybe 1/2 quart with tune.

 

[Digital4n6]

I did take off the strut brace. There were the 3 bolts each side, 2 near the windshield. The EDU has 2 nuts and 2 guide pins (under the windshield) holding it in place. Just remove them as it'll give you lots of room to work on getting that big SCR can on he oem downpipe out.

 

[Mcdmarkd]

thanks working on getting the shield out

 

[Mcdmarkd]

Dpf is out any links to egr delete Thanks for the extra info

 

[Digital4n6]

I have blockoff plates for the EGR from Darkside but haven't installed. Tune turns off the egr valve.

 

[commedeschatons]

EGR Blockoff Plate Install DIY for North American 3.0 TDIs

www.clubtouareg.com

 

[commedeschatons]

any links to egr delete

blockoff plates makes the most sense to do first esp if you have the dp off

Blockoff plates:
SUSTDI ($35+US shipping)
Darkside ($55+intl shipping)

Cooler delete incl. plates:
SUSTDI ($220+us shipping
Darkside ($275+intl shipping)

 

[under dog]

I am bumping this up and asking a question. I have a 2015 A8 tdi and am researching dpf delete kits. I found the darkside kit, but my question is does the darkside pipe only delete the dpf and not the cat? OP, did you also delete the cat?

I already have the Malone stg2 tune. Just want to do the dpf delete as well. I didn't see as much of mpg increase as I wanted with just the tune. I've actually seen a decrease in the last couple years, down to low 30's mpg. I was getting 36-39 mpg stock, but with close to 140k now its not as good.

 

[Digital4n6]

There are 2 cats, one on the downpipe with the SCR stuff, another on the lower exhaust pipe. The second one has almost no performance effect so no need to "straight pipe" it, which may actually lead to a drone sound.

I have the Malone State 2 tune, and recently installed the Oakes TCU tune, which really made a difference in "sport" mode. My mpgs are probably around 34mpg tank average, higher on long highway road trips.

One thing that REALLY bugs me is the absolute horrendous soot smell after the delete since it's not captured by the SCR stuff. Windows up, recirculating air (not fresh) every drive. Might calm down after a lot of the soot buildup is burnt off from internals, but it drives me crazy. When I do the coolant gasket and other delete items from SUSTDI, I'll clean the intake manifold, there was a lot of gunk all up in that.

 

[under dog]

So does the DS dpf pipe also get rid of that 1st cat as well as the dpf?

Im thinking I also need to take the intake manifold off and do some cleaning as well, I wonder if that's part of the reason I've seen my mpg decrease recently.

 

[danmin]

So does the DS dpf pipe also get rid of that 1st cat as well as the dpf?

Im thinking I also need to take the intake manifold off and do some cleaning as well, I wonder if that's part of the reason I've seen my mpg decrease recently.

go with NAT Performance. nice guy. low prices. best tuner partnered with him. Oakes Performance.

 

[dlhovland]

So does the DS dpf pipe also get rid of that 1st cat as well as the dpf?

Im thinking I also need to take the intake manifold off and do some cleaning as well, I wonder if that's part of the reason I've seen my mpg decrease recently.

On my 2015 Touareg I left the down pipe with cat in on Just removed Dpf and box cat . No smell at all