Test pipe and O2 spacer with catalyst

[xstwin]

jordancl, quick question.... When you first installed the 034 HFC w/ "optional spacer" was the obdII code 2096? My understanding is the 2096 is a lean condition relative to the pre-cat lambda sensor. Meaning the catalyst is "too efficient", and the secondary lambda sensor is reading too much of a variance from the primary one. Couple of quick things to try. Tighten all bolts and remove all spacers.

[jordancl]

The codes I got were in the order I posted above, so yes, I got the lean code first, then the rich code, then the 'broken cat' code. I have nearly a year until I'm up for an inspection so I have no problem removing all spacers and trying that too :)

[wabbit23]

This sucks, maybe the straight spacer is the way to go. I'm just under 1500 miles with no issues.

[jwagner0482]

Keep working on it guys. Nice to see you are testing and reporting the results

[kmjmrq]

90-spacer installed.. so far 30 miles.. no CEL......

[fatboyj711]

Based on the limited sample so far, it looks like 90 degree spacer still throws a CEL and the straight spacer is the way to go. As mentioned before, thanks for testing this out and reporting your results.

[The Infiltrator]

90-spacer installed.. so far 30 miles.. no CEL......

Did you install the HFC and the spacer yourself? If so how hard was it to DIYS?

[kmjmrq]

I had shop install HFC and spacer... DFW area is blessed with Zinks Garage...

[The Infiltrator]

Nice job on it! Has anyone on this thread DIYS?

[ItsDubC]

Nice job on it! Has anyone on this thread DIYS?

It's a huge PITA to DIY on the B7, not sure how similar it is on the B8 but it seems like something I'd definitely have a shop do.

BTW, has anyone tried or considered using spark plug non-foulers on a B8 testpipe or HFC?

[wildbill]

BTW, has anyone tried or considered using spark plug non-foulers on a B8 testpipe or HFC?[/QUOTE]

bingo

[jordancl]

I did the HFC install (actually my VW tech friend did it and I watched mostly) and it was a huge PITA. The spacer though is easy if you have some patience and a wrench.

[xstwin]

I installed a test pipe twice in my driveway using 2 jack stands. Getting the OEM pipe out took 2hrs but that included getting the car up in the air and stable. I tried the removal through the engine bay as some others have done, but no luck for me. Got it out from below. As an aside, I wrapped the pipe in high quality exhaust wrap secured with full stainless hose clamps. Not much louder than stock, but with an angry growl when throttled. OEM exhaust beyond that. Oh, I'm on a stage 2 tune now which definitely adds some pep.

BTW, here's the process, courtesy of wabbit23 (hope you don't mind that I post this).



Before you disconnect any sensors
disconnect your batteries negative terminal. Then go ahead and remove your under panel. I wouldn't recommend removing your stock airbox yet due to accidentally dropping something into your turbo. You'd end up with a bad day.

1. Tools- 3/8 drive ratchet with 6" ext and O2 sensor socket.
Diconnect and remove the primary O2 sensor. You can remove the secondary if you like but it isn't a necessity at this point.

2. Tools- 15mm ratcheting wrench or regular wrench.
Remove the two visible bolts and the engine side top bolt from the point the cat/turbo connection. Some PB Blaster or any of that type of bolt loosening stuff comes in very handy!!!

3. Tools- 13mm wrench and 13mm socket and 1/4drive ratchet.
Remove the brace that has the spring on the side of the Cat. The bolt that is holding the bushings part removes the whole thing but you want this off completely since getting the cat out alone is pretty much a pain in the ass.

4. 15mm socket, 3/8 drive ratchet and a 9 inch extension.
Towards the front of the engine there's a small hole just big enough to squeeze your hand through and guide the socket onto the nut. You want to have the ratchet towards the back of the cat where you removed the spring/brace from. This will remove the last nut from the cat/turbo connection.

5. Remove the 3 nuts and bolts from the cat/midpipe connection. I had a 1/4 Allen key and 12mm wrench but you might have different hardware here. (I had 12mm nuts only)

6. Once all hardware is off the cat remove the stock airbox. This will allow just enough room to take the cat out from the engine bay. You have to play with it a little but it will come out from the top. Just keep twisting and pulling and finagle it until it comes out. (again, I couldn't get it from the top. removed exhaust mid pipe at clamp with 13mm nuts, then dropped OEM cat out).

7. Put your new pipe in and put everything back on. Reconnect all sensors and battery and turn key. ( I put new test pipe in from underneath as well, with spacers and O2 already installed.)

[ItsDubC]

^Awesome info there, xstwin. Thx again and thx to wabbit23!

[jordancl]

jordancl, quick question.... When you first installed the 034 HFC w/ "optional spacer" was the obdII code 2096? My understanding is the 2096 is a lean condition relative to the pre-cat lambda sensor. Meaning the catalyst is "too efficient", and the secondary lambda sensor is reading too much of a variance from the primary one. Couple of quick things to try. Tighten all bolts and remove all spacers.

Removed all spacers and plugged in straight o2 sensor. 22 miles and CEL ** P0422 efficiency below threshold as expected. No code for too lean without any spacer. Put the spacer back in and 18 miles later got the P2096 ** too lean. This is causing a MIL but I am not getting a P0422 with spacer. I also got this same code with the 034 optional straight spacer. Maybe I'm doing something wrong on my end :(

[xstwin]

Oh you're gonna hate me for this one......Try another post-catalyst sensor. Sound's like the one you have in your car is very high tolerance (too sensitive). When they manufacture those things, not all are created equal. Otherwise, if you're really adamant on making this work with your current setup, the best solution is to put a dual channel oscilloscope on both sensors and compare the reading. While they shouldn't be the same, the delta between the two signals should be sufficient to "fool" the ecu that all is Ok. Sorry to geek out on you, but the days of the carburetor are long gone.

[wabbit23]

No problem. I was going to try and do a full write up but I didn't have any pictures so I figured I'd just take some, edit them with arrows and then post the diy. I hope the collective write ups help other diy'ers on here.

Oh and she's still going strong without any issues except for a little worse mpg's. (I tend to stay on the boost a little more!)

[jordancl]

Oh you're gonna hate me for this one......Try another post-catalyst sensor. Sound's like the one you have in your car is very high tolerance (too sensitive). When they manufacture those things, not all are created equal. Otherwise, if you're really adamant on making this work with your current setup, the best solution is to put a dual channel oscilloscope on both sensors and compare the reading. While they shouldn't be the same, the delta between the two signals should be sufficient to "fool" the ecu that all is Ok. Sorry to geek out on you, but the days of the carburetor are long gone.

O2 sensors are not cheap and I don't want to buy another one and have a similar issue. I might consider swapping the front and the rear, but I'm not sure. The other option that seems more presentable to me at the moment is to try to space the sensor out a smaller distance to avoid the 0422 and the 2096. The 90* sensor comes in two pieces, the mini cat, and then spacer. I wanted to try to screw the o2 sensor directly into the mini-cat, but it seems the threads are not the same. If only there was software to ignore P0422 AND keep the second o2 sensor ready/active :(

Most important thing to add to this thread is that I have absolutely no evidence that the Strat spacer "doesn't work". In fact, if anything it seems to work too well, but so did the 034 basic spacer.

[a4_bob]

Thanks for your feedback @jordancl. As I understand this the front O2 sensor and MAF contribute to air trim calculations while the rear O2 sensor is simply monitoring the cat? i'm new at this but based on the trim readings varying with the presence of the spacer, it almost sounds like you're putting the spacer on the front sensor. ?? does the rear O2 sensor contribute to trim calculations? if so, how would a spacer or disabling it via APR stage2 actually work right?

I'm quite curious to fully figure this out as I just received my HFC and 90* spacer and am wanting to run this w/ the rear O2 sensor active+no cel and no faults.

[xstwin]

jordancl, I've got an extra 1/4" spacer (more like washer) that will thread onto the 02 sensor. Should leave about 2.5 threads left. I'm in NJ, will gladly drop it in the mail. Send pm if interested.

[jordancl]

Thanks for your feedback @jordancl. As I understand this the front O2 sensor and MAF contribute to air trim calculations while the rear O2 sensor is simply monitoring the cat? i'm new at this but based on the trim readings varying with the presence of the spacer, it almost sounds like you're putting the spacer on the front sensor. ?? does the rear O2 sensor contribute to trim calculations? if so, how would a spacer or disabling it via APR stage2 actually work right?

I'm quite curious to fully figure this out as I just received my HFC and 90* spacer and am wanting to run this w/ the rear O2 sensor active+no cel and no faults.

This is the way I understand it. The front O2 sensor reads exhaust gasses going into the cat for hydrocarbon levels. The rear sensor reads exhaust gasses coming out of the cat and reads for hydrocarbons also. If the cat is functioning, there is a decrease in hydrocarbons in the exhaust gas at the rear o2 sensor because the catalyst has converted them into CO2 and H2O.

With no spacer and a high flow cat, the rear o2 sensor is seeing more hydrocarbons than it would w/ the stock cat because the gas is passing through the cat more quickly and it is not converted as well. Of course the car doesn't know or care that you put in a higher flow cat; all it knows is that its seeing too many hydrocarbons after the cat and it throws a P0422 ** cat below efficiency threshold. The car essentially thinks your catalytical converter is broken.

Putting a spacer in steps the o2 sensor back out of the cat so its not right in the middle of everything. The idea behind a spacer is to not let the rear o2 sensor see some of the hydrocarbons in the exhaust gas so it thinks everything is OK and it doesn't flip out as above. However, as I stated originally, the rear sensor does expect to see SOME hydrocarbons because even the stock cat isn't perfect. So if you space it out too far, and it doesn't see ANY hydrocarbons it figures there must not be enough gas getting to the engine (running lean).

As far as I can tell, I'm the only one who has had a problem like this on the forums thus far, so if you have a spacer in your hands I'd just throw it on and try!

jordancl, I've got an extra 1/4" spacer (more like washer) that will thread onto the 02 sensor. Should leave about 2.5 threads left. I'm in NJ, will gladly drop it in the mail. Send pm if interested.

I will definitely try this and paypal you shipping $$ ** PM sent

[ItsDubC]

Ya I would think that if the spacer is working for ppl w/ testpipes, it should definitely be working for ppl w/ HFCs

[kmjmrq]

500 miles- NO CEL... state inspection coming up on September...

[a4_bob]

With no spacer and a high flow cat, the rear o2 sensor is seeing more hydrocarbons than it would w/ the stock cat because the gas is passing through the cat more quickly and it is not converted as well. Of course the car doesn't know or care that you put in a higher flow cat; all it knows is that its seeing too many hydrocarbons after the cat and it throws a P0422 ** cat below efficiency threshold. The car essentially thinks your catalytical converter is broken.

right, the rear sensor detects in the same way as the front but with different intent; broken cat vs fuel trim. I don't understand why the rear sensor would take part in fuel trim functions. It still sounds like something's off up front, as StratJohn was suggesting some posts earlier. The spacer on the rear almost sounds coincidental. Just my noob reasoning...

Good luck getting it straightened out. I'll post my results next week after installation.

[jordancl]

Sounds like it may be coincidence, but I don't get a lean error with no spacer... I dunno, hopefully I can figure this out

[ItsDubC]

This might seem dumb and it's probably not the issue, but I just read an old post in a Passat forum where a dude was getting P2096 after he had some work done to his car. It turns out that the tech accidentally criss-crossed the plugs and sensors during re-assembly. The Passat-owner swapped his front and rear O2 sensors and everything was gravy.

[StratJohn]

This might seem dumb and it's probably not the issue, but I just read an old post in a Passat forum where a dude was getting P2096 after he had some work done to his car. It turns out that the tech accidentally criss-crossed the plugs and sensors during re-assembly. The Passat-owner swapped his front and rear O2 sensors and everything was gravy.

I think that happens more often that not- I was guilty of that on one of my first V8 cars.. two dangling sensors side by side? Pfft thought I had them right....

[ItsDubC]

Any luck w/ this, jordan? Sensor swappage?

[jordancl]

As far as I can tell it would be pretty close to impossible to have the front and rear sensors switched accidentally because they're different colors and the front cable is significantly shorter and bracketed to the front. See the pic above:

http://www.audizine.com/gallery/data.../o2spacer1.JPG

I haven't worked on it at all yet, I had a pretty busy weekend installing the s/t shifter and drinking beers. I'm getting less concerned because despite having the CEL on all my readiness tests are passing, so I know I could pass NYS inspection just by clearing the CEL prior to getting inspected. I still am interested in getting rid of the CEL completely, but since my problem is different than everyone else's on the forum I'm kinda flying solo here. Will probably try spacing out the sensor less far but it's not my #1 concern atm.

Can anyone with the stage 2 testpipe file confirm via vag-com scan (OBDII functions > 03 - Readiness) that you have multiple not ready / failures?

[ItsDubC]

^Cool. Just wanna see you get up and running error-free. The issue is just weird lol

[a4_bob]

I just put about 20miles on a Eurocode HFC and the stratmosphere 90* spacer. So far so good. I'll put some more miles on, do some scans and report back.

[ItsDubC]

^Nice! Did you verify readiness w/ VAG-COM by any chance?

[jordancl]

FYI vagcom has me showing ready for all tests despite the CEL for too lean. If I run w/o the spacer and I get cat inefficient CEL, all are ready except the CAT test fails. Either way, it seems I could clear the CEL and pass inspection as is right now.

[a4_bob]

^Nice! Did you verify readiness w/ VAG-COM by any chance?

Verified readiness, no cel or faults. Off to a good start but I'm only on day one; I did have a nice mix of slow/fast/easy/aggressive/city/hwy driving.

[jordancl]

right, the rear sensor detects in the same way as the front but with different intent; broken cat vs fuel trim. I don't understand why the rear sensor would take part in fuel trim functions. It still sounds like something's off up front, as StratJohn was suggesting some posts earlier. The spacer on the rear almost sounds coincidental. Just my noob reasoning...

Good luck getting it straightened out. I'll post my results next week after installation.

I checked my codes for the cat two days ago and noticed I had the lean code 7/25, and then the too rich code a few days later. I cleared the codes hoping that the ECU would find the right mix to keep the sensors happy w/ the spacer, but I got a CEL about 30 miles later. Checked that code today and it's too rich. I'm pretty sure this rules out an exhaust leak from loose bolts or faulty gaskets, but I'm not sure. To be continued I suppose...

[a4_bob]

Readiness test now shows 1 fault which showed up two days after the install - Lean from the post catalyst O2 sensor. No CELs (yet).
damn...

[ItsDubC]

Readiness test now shows 1 fault which showed up two days after the install - Lean from the post catalyst O2 sensor. No CELs (yet).
damn...

Hmm... so the spacer may be working too well?

[a4_bob]

Maybe but I'm going to keep an eye on it to see if it's stable in that way. If it is, I may try taking the 90* piece off and going with the straight mini cat spacer (I'm pretty sure that would fit). That might provide a richer reading and be the right setup since I'm running a HFC and not a test pipe. It appears to be a delicate balance.

[jordancl]

bob, I think I tried that and my o2 spacer did not thread into just the mini cat portion

[ItsDubC]

I can't really tell by the pic of the 90º spacer, but is there a way to remove the mini cat but keep things spaced out?