Rear O2 Sensor Extension Needed?

Exhaust modifications

Rear O2 Sensor Extension Needed?

Postby Shaheenis » Thu Jan 16, 2014 7:39 am

Summary of Findings: You don't need an O2 extension for any aftermarket CAT unless it is being installed further back than the original mid-pipe flange (highly unlikely). Please see posts towards end of thread for more detail.

Hi there,

I have searched and found no reference to this topic before which makes me wonder whether it is even an issue. I am planning to fit the new dump pipe probably this weekend. One of my mates had issues with the his rear O2 sensor not being long enough to reach the bung hole on his MY08 STI WRX so I got under my car for a quick look last weekend. I didn't have great access but it seemed like there was no slack in the cable and I need it to stretch an extra 30cm to get to the rear O2 bung on the new dumpster. Anyone who can advise on the slack length in this cable or having hit this issue previously would be appreciated.

Cheers,
Last edited by Shaheenis on Thu Feb 06, 2014 5:08 pm, edited 5 times in total.
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Re: Rear O2 Sensor Extension Needed?

Postby mynameisdaniel » Thu Jan 16, 2014 4:31 pm

My Phat dump only rotated the position slightly, no extra slack needed. But it will depend on the dump pipe you get. Watch how you route the wires too as an exhaust shop changed my routing and my gearbox ended up crushing mine in half...
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Re: Rear O2 Sensor Extension Needed?

Postby jaydece » Thu Jan 16, 2014 8:21 pm

Shaheenis wrote:Hi there,

I have searched and found no reference to this topic before which makes me wonder whether it is even an issue. I am planning to fit the new dump pipe probably this weekend. One of my mates had issues with the his rear O2 sensor not being long enough to reach the bung hole on his MY08 STI WRX so I got under my car for a quick look last weekend. I didn't have great access but it seemed like there was no slack in the cable and I need it to stretch an extra 30cm to get to the rear O2 bung on the new dumpster. Anyone who can advise on the slack length in this cable or having hit this issue previously would be appreciated.

Cheers,


Relocate the bung....or get another one and block the other one....
~JUSZTN~

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Re: Rear O2 Sensor Extension Needed?

Postby Shaheenis » Thu Jan 16, 2014 8:59 pm

It has 3 bung holes. The problem is I want to use the one closest to the flange as this is post cat..
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Re: Rear O2 Sensor Extension Needed?

Postby jaydece » Fri Jan 17, 2014 3:15 pm

Shaheenis wrote:It has 3 bung holes. The problem is I want to use the one closest to the flange as this is post cat..


turbo xs dump?

okay then? relocate the cat? I would chop it off and reposition it something similar to a phat dump or similar product? then you wont need wiring extension...

so basically you could do this after:

bung 1 - AFR or EGT or similar
bung 2 - post cat sensor
bung 3 - AFR or EGT or similar

either way looks like your great buy is going to end up costing the same/or more as a dump that you could of bought that would be ready for straight fitment with less hassles....
~JUSZTN~

** Our Turbo Lag Gives Those v8's A Chance **

History - MY07 Liberty TBSTI 6SPD Sedan
265kw atw on P100
290kw atw on E85 (fuel pump limited)


Past - MY16 Audi S3 Sedan
249kw atw on P98 (APR stage 1)

Present - MY18 Audi RS3 Sedan (His)
384kw atw on E85 (APR stage 2)

Present - MY17 VW Tiguan 162 R line (Hers)
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Re: Rear O2 Sensor Extension Needed?

Postby Shaheenis » Fri Jan 17, 2014 9:21 pm

jaydece that is not really useful feedback mate. Who in their right mind would cut up an aftermarket dump pipe to re-position the CAT when they could spend 15min extending the O2 cable with a soldering iron or disable the CEL? I am after feedback from others that have done this and options to do this, not comments about the dump pipe and whether you think it is a good deal, I am happy to compare with what you spent and why yours is so much better? I could spend $400 resolving this and still be in front.. I actually don't need any help on this but I like to learn from others experience but to be totally honest it is hard to get constructive feedback on this forum.
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Re: Rear O2 Sensor Extension Needed?

Postby jaydece » Fri Jan 17, 2014 10:02 pm

Shaheenis wrote:jaydece that is not really useful feedback mate. Who in their right mind would cut up an aftermarket dump pipe to re-position the CAT when they could spend 15min extending the O2 cable with a soldering iron or disable the CEL? I am after feedback from others that have done this and options to do this, not comments about the dump pipe and whether you think it is a good deal, I am happy to compare with what you spent and why yours is so much better? I could spend $400 resolving this and still be in front.. I actually don't need any help on this but I like to learn from others experience but to be totally honest it is hard to get constructive feedback on this forum.


not useful? really......okay fair enough...but from my end I believe I'm trying to give some valid suggestions...

who in there right mind would go down this path?.....sorry for being crude....for me I don't get it...

what I've spent? I've spent allot of time and effort.. and have tried many combinations in trying to get my aftermarket dumps modified to suite .....not make things suite around the dump....this includes flex joints....there that's 1 constructive point maybe for you...

I assume most people would do the same?....probably why your finding it hard to find people who havent done this? :shock:

do you know what the post cat 02 sensor actually does?... and how important the factory position needs to be? when installing it...hence why I suggested to move the cat and position the bung close or near the factory location.... correct me if I'm wrong here someone...

I have a feeling if you go with this extension? you'll pop a cel anyway.....why? different position, your new cat is probably a 100cel? 200cel cat? different from the oem one..not to mention the extra flow....efficiency, emissions...etc etc......

if your going to disable it? then whats the whole point in having this discussion.....you might as well disconnect it now and block it up and disable the cel...

sorry my feedback isn't constructive enough.....
~JUSZTN~

** Our Turbo Lag Gives Those v8's A Chance **

History - MY07 Liberty TBSTI 6SPD Sedan
265kw atw on P100
290kw atw on E85 (fuel pump limited)


Past - MY16 Audi S3 Sedan
249kw atw on P98 (APR stage 1)

Present - MY18 Audi RS3 Sedan (His)
384kw atw on E85 (APR stage 2)

Present - MY17 VW Tiguan 162 R line (Hers)
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Re: Rear O2 Sensor Extension Needed?

Postby Shaheenis » Fri Jan 17, 2014 10:41 pm

Jaydece I understand how the exhaust and O2 sensors works and the importance of positioning, hence this thread!!!!! A lot of ppl take the easy route and disable the CEL so that is why no one has probably raised this before. Me? I like to explore different options and don't like tuning around it if I can avoid it as it becomes someone elses problem down the track when they put a stock tune back on it. It is about doing things right but for me that doesn't mean spending $900 on a 'popular' dump, when the design isn't even that great, to avoid one problem and be faced with the next (steering knuckle, heat shield trimming, no cat etc.)

I don't even know that O2 won't reach and that it is actually a problem if you read my opening post, I am planning for the worst as I don't want to be caught half way through a job with a surprise. The purpose of a forum is to learn from others who have been there done that.

The turboxs is actually very well equipped with 3 x O2 positions available but I would prefer to install as close to factory as possible. Regards to the cat, the factory 2nd O2 is installed between the first and second cat. Assuming the aftermarket CAT isn't hugely different from the pre-cat (possibly 1/3rd of the overall CAT conversion performance based on size) on the stock system it should be perfect. This same issue is faced by ANY aftermarket dump and CAT. I have done a lot of research on extending the cable and believe I can do it cleanly and professionally for $15 and 30min of my time. I was hoping someone could tell me how much slack was in the factory wires to avoid having to do this.

I didn't mean to be rude it just seems I get more opinions than actual assistance on these forums than I am use to.
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Re: Rear O2 Sensor Extension Needed?

Postby Shaheenis » Sun Jan 19, 2014 10:18 am

I can now confirm that an O2 extension cable is not needed to fit any aftermarket dump as with re-routing there is ample length in the loom. The O2 sensor runs a short loom (about 50cm) to a female plug connector on the passenger side of the gearbox. The female plug connector belongs to a plug in wiring extension (about 70cm) that connects under the intercooler adjacent to the pitch rod. You can disconnect and remove both from the car easily with some needle nose pliers (to squeeze while you push the cable clip retainers) and your fingers to push the tab on the zip ties to undo and release the cable.

By undoing the cable ties and freeing up the loom you can get an extra 15-20cm (using same routing on passenger side).

By removing the cables and re-routing down the driver side you can get an extra 30-40cm (enough to easily meet the mid-pipe flange). I haven't completed the install yet, will be later this afternoon but I will take special care to route and secure the cable in such a way that it can not be crushed by any moving parts (including gearbox movement) and such that it can not come in contact with the exhaust. The cable is heat shielded but I will likely put some more conduit around it just for some extra protection. With regards to the turboxs dump, I suspect I may need to nip a bit of tin out of the underbody heatshield to allow the O2 sensor clearance but will update hopefully tonight.

Cheers,
Shaheenis
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Re: Rear O2 Sensor Extension Needed?

Postby Shaheenis » Sun Jan 19, 2014 7:43 pm

This job is now complete :). I will start a different thread for TurboXS dump install but I am pleased to say that everything bolted up perfectly, original mounts and all. There are a couple of small things to be prepared for but I will elaborate in a separate thread. Given this thread is about the O2 extension, I ended up routing the O2 sensor lead via the original path (passenger side) and used all of the original cable tie points except for 1 where I used a zip tie.

I decided against the driver side as although it gives you extra length you don't need it and the bigger issue is that with the positioning of the O2 sensor that the wiring needs to cross the path of the prop shaft when tucked up above the heatshield. You could tie it down but I don't think this is good practice so I used the original path. Here is one photo of the O2 position post CAT on turbo XS before I trimmed the heat shield and routed the able.

Image
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Re: Rear O2 Sensor Extension Needed?

Postby Shaheenis » Mon Jan 20, 2014 5:12 pm

Image

More pictures showing measurements and part number:
http://s1293.photobucket.com/user/shahe ... %20Install

New thread covering install etc
viewtopic.php?f=55&t=25017&p=358172#p358172
Shaheenis
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