TheAvgBear

Like the title says, have any of you with a 2.7 removed the mid cats? For some reason my allroad doesnt have flanges or flex pipe north of the mid cats. I plan on doing some work to the tranny to solve my leak probelms, but i can only remove the last half of the exhaust (there are flanges after the cats, under the driveshaft. So the cats and exhaust are under the tranny in the way, unless I remove the downpipes from the turbos, which looks next to impossible!

So my plan to get access to the transmission was, to go to a nearby shop and have buddy add flanges farther up on the front side of the cats so that i can come home and take the exhaust off.

I live in Canada and don't have emission tests to meet. The ar has 185,000km (115,000mi), so the cats are prob near the end of their lives anyway. I was thinking of maybe just removing the cats completely, adding new pipe and freeing up some back pressure. I've been looking into the issues with the O2 sensor all afternoon, and i've only really came accross write ups about the o2sensor on the pre or upper cats directly after the turbos. So i'm just wondering if anyone of you have removed the mid cats, and if so what did you do to the O2 sensor to avoid a CEL? Just remove it from the cat, add a bung for it in the pipe and use spacers or non-foulers? Does this work for the 2.7? Anything else a junior like me should be aware?

Outtyinmeaudi

Id like to know as well

Metronet

For the APB Allroad the turbo back downpipe is one unit. I have removed the pre-cats to make them into piggies but left the main cats. I think the BEL engine has a different flange on the turbo side and the heat shields are two pieces.

When removing the downpipes I did it without loosening the subframe on a Tiptronic. If you have a 6 speed it might be easier?

TheAvgBear

I have an 04 allroad with the tiptronic, so that would be the BEL engine I believe. The downpipes are are one unit (ie. both cats are on one continuous pipe from the turbos). There is only one flange on the entire exhaust, it is in the middle of the car under the driveshaft. I would love to do piggies, but the downpipe bolts on the turbos look impossible to get at, and its a northern vehicle so Im scared to snap one and be worse off than I am right now. I may attempt to gut the precats in the future, but for now I need to get my transmission leak(s) solved.

TheAvgBear

AudiWorld Tech Articles

I came across this write-up just now, that talks about adding a diode to trick the ecu into reading the correct O2 voltage. Buddy seems pretty confident about the technique. But it is directed at getting a correct reading because the precats have been gutted. Anyone try this? Or know if the same technique would work for my scenario? With having the precats left alone, but removing the midcats and just having the o2 sensor directly in the pipe

P4Ring

Don't know of anyone who done this but the down pipes removal is not so bad.





Disconnect oxygen sensor connectors and remove bracket from fire wall. Green black = RH. Brown black = LH





Remove this cover on the left side. Unclip and pull out.





LEFT SIDE ONLY: Remove harness bracket from fire wall and move engine wire out of the way. Remove anything else you see that will prevent access





Remove the bottom bolts from the transmission mount, then use a jack to slightly lift the transmission from the back end which in turn will tilt the engine forward thus given you room to access the upper turbo flange bolt on the left side. (Be careful not to damage engine mount or snub mount)





Use a 17mm angled/offset wrench (use the close end) to loosen turbo flange bolt. It may be necessary to extend the leverage with a piece of pipe. If bolt/nut is in bad condition pre treat it with penetrating oil to prevent breakage.





On the right side remove, Air filter box, EGT sensor probe and the upper turbo flange bolt (1). Remove hex bolt fasteners from heat shield on BOTH sides.





From under the car, remove the other 3 flange bolts. Ratcheting wrench work good on these. (Better to have the flex ones but more expensive)





Loosen the lower heat shield clamp.






Bring down the oxegen sensor wires
Unclip wires from the transimission
Disconnect downpipe from rear section.
Jiggle out downpipe from heat shield and off turbo flange

Remove downpipe with oxygen sensors still in place

DO NOT TAKE OUT THE LEFT SIDE HEAT SHIELD...LEAVE IT IN. (Can't say I didn't warn you) Guide the oxygen sensor wires and harness out of the heat shield and remove down pipe. A second person may be necessary to prevent damage to the flex joint.

Loosen the clamps that connect the downpipe to the rear

That's all I can remember, good luck.

Outtyinmeaudi

Awesome, thank you.