Author Topic: Need two o2 sensor bungs in the downpipe?  (Read 19286 times)

Offline CornOntheCobb

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Need two o2 sensor bungs in the downpipe?
« on: April 12, 2012, 10:57:49 AM »
So I thought I had my TBE setup picked out but then I learned that the downpipe I want (Invidia v3) only has one bung. How important is it to have an extra o2 sensor bung for a wideband in the dp? My plans were to just get a TBE for now and get re-flashed to Stage 2 via the Cobb AP. An intake, uppipe, and header might be in my future just not right now so I figured Iíd be okay with the Stage 2 map from Cobb.

I like that the Invidia v3 is catless, the divorced style and well... that itís Invidia. It will pair nicely with the Invidia n1. I realize I could always have an extra bung welded in later but I donít want to mess with that. Iím sure itís not difficult and there are people who do quality work but Iím kinda particular about these things. If I really need two o2 bungs then I want to buy a dp that already has them. Why doesnít Invidia just offer a catless, divorced dp with two bungs?

Offline C.J.

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #1 on: April 12, 2012, 11:14:03 AM »
No after market dp comes with a bung in the proper place for a wideband o2.  Just buy a bung and have an exhaust shop weld it in.

Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #2 on: April 12, 2012, 11:26:01 AM »
No after market dp comes with a bung in the proper place for a wideband o2.  Just buy a bung and have an exhaust shop weld it in.
Proper placement for wbo2 is highly debatable. The both the catted and non-catted CNT downpipes come with wbo2 bungs in the top of the bellmouth and both have served me well.

You don't need the wbo2 with just your TBE, but it is highly recommended if you are changing your intake. You may be able to fudge your MAF scaling to get it close enough, but you really can't tune an aftermarket intake without a wbo2.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com

Offline C.J.

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #3 on: April 12, 2012, 11:29:22 AM »
Those bungs right at the mouth of the dp are for egt probes IMO.   A wbo2 will burn up/reduce the life of the sensor.  36" from the turbo is the ideal location in my experience. 

Offline jaz

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #4 on: April 12, 2012, 11:43:16 AM »
EGT should be close to the exhaust ports for truly useful data. With the turbo so far from the exhaust ports, the WBO2 placement is already pretty far down the line. In low flow situations, I can watch the delay in readings when logging.

The stock sensor is much closer to the the hotter part of the exhaust path and those get used for 60k miles or so.  I personally like the placement about 6" away from the turbo on these cars.  The fact that these cars need to be run so rich to be safe will likely kill the sensor first.

Offline swfire271

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #5 on: April 12, 2012, 11:43:49 AM »
No after market dp comes with a bung in the proper place for a wideband o2.  Just buy a bung and have an exhaust shop weld it in.
Proper placement for wbo2 is highly debatable. The both the catted and non-catted CNT downpipes come with wbo2 bungs in the top of the bellmouth and both have served me well.


I'm getting ready to install my cnt catless pipe....have you had any sensor failures or issues with a daily driven vehicle using the bung that comes with it?
Previous Subarus:
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Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #6 on: April 12, 2012, 11:54:20 AM »
That's why it is highly debatable. You have your personal experience and I have mine.

When I first installed my LC-1 in that location, I got error code 8 (sensor timing/over heat) all the time. I even bought a second sensor and still got the problem right away. I looked up in the LC-1 manual (http://www.innovatemotorsports.com/support/manual/LC-1_Manual.pdf) and found that the sensor is only rated for 900*F at the bung. So I borrowed a laser thermometer and measured ~500*F at the bung after a long hard run. I decided that the sensor couldn't be overheating and did some more research.

I found that the manual only states to install the sensor downstream of the turbo, not a specific location. I also found many others complaining in forums about error code 8 and finally came across the suggestion to downgrade the firmware from 1.10 to 1.00a. I've now been running an LC-1 for 2 years continuously at the top of the downpipe with no problems. I do periodically calibrate it, but I have never received another error and it has been an excellent tuning tool.

So again, highly debatable based on personal experience.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com

Offline joeleodee

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #7 on: April 12, 2012, 06:38:31 PM »
^ what he said.  I've never changed my sensor and I haven't had any problems in the same 2 years.  I've got an invidia catted and the bung is welded at the bellmouth before the cat. 

Offline kevinmfb

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #8 on: April 13, 2012, 07:57:22 AM »
If the downpipe isn't installed already go ahead and get the bung welded in.  That way you won't have to take the downpipe off your car when you do decide to get a wideband.
A muffler shop can weld that up quick and easy for ya and it shouldn't cost much at all.

Offline joeleodee

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #9 on: April 13, 2012, 08:08:43 PM »
Yeah, shouldn't be expensive as long as the bung is not welded into the cast stainless steel bellmouth.  Since it is catless, you have the option.

Offline Trick

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #10 on: April 13, 2012, 09:44:37 PM »
The Shop INC in lincoln welded up a bung in my stainless exhaust for my truck for ~$20 with the pipe off the vehicle.

Offline CornOntheCobb

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #11 on: April 17, 2012, 10:50:49 AM »
So if I have this right, a wideband o2 sensor is necessary for any custom tune, which would be recommended for anything beyond a TBE? And placement on the dp is debatable?

Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #12 on: April 17, 2012, 11:24:18 AM »
Correct except for the "necessary for any custom tune". It is highly recommended (considered necessary by me personally), but tuners will do custom tunes even if you do not have a wbo2. I had a custom stage 2 e-tune done when I first got my car in 2009 without using a wbo2. It wasn't the best experience, but it did keep my car from blowing up.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com

Offline tank

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #13 on: April 17, 2012, 11:34:12 AM »
Correct except for the "necessary for any custom tune". It is highly recommended (considered necessary by me personally), but tuners will do custom tunes even if you do not have a wbo2. I had a custom stage 2 e-tune done when I first got my car in 2009 without using a wbo2. It wasn't the best experience, but it did keep my car from blowing up.

lol not word for word, but thats exactly what I tried posting and when I hit post, it said there was a reply already..

This is 100% true. It's not necessary, but is very nice to have.

Offline CornOntheCobb

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #14 on: April 18, 2012, 08:47:04 AM »
Excellent, thanks! So are there any divorced style downpipes that already have 2 bungs installed and are catless? I would prefer to avoid having a shop weld in an extra bung.

Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #15 on: April 18, 2012, 11:30:19 AM »
I am not aware of any? Why are you specifically looking at divorced? I understand and appreciate the theory of the benefits of divorced, but I've not seen hard evidence of it being better in the real world.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com

Offline csmiller18

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #16 on: April 18, 2012, 03:22:00 PM »
I am not aware of any? Why are you specifically looking at divorced? I understand and appreciate the theory of the benefits of divorced, but I've not seen hard evidence of it being better in the real world.

I just did a little research regarding the theory of the divorced benefits you are referring to, but to clarify, its supposed to separate the two streams of exhaust flow to reduce turbulence? is that correct and is that all the possible benefits?

Not trying to thread steal...
2005 WRB STi
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2005 HONDA TRX450R

Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #17 on: April 18, 2012, 04:20:40 PM »
That's basically it. The smoother the flow, the better. Still, I'd think the turbo in general adds some turbulence, and adding additional turbulence from wastegate flow in the real world doesn't seem to make much difference. Additionally, when you're building boost, the wastegate is going to be mostly closed, which would further reduce any negative effect.

Now, if you look at the stock downpipe, that is a totally different story. The wastegate exhaust is directed toward a completely flat wall. That does have the potential to cause problems.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com

Offline CornOntheCobb

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #18 on: April 18, 2012, 07:03:21 PM »
Right, the thought process is that the greater the separation there is between the wastegate gases and exhaust gases, the smoother the overall exhaust flow. I appreciate the theory and realize there's no concrete proof that the divorced style is better but the option's there... why not opt for it? ....Well for me if there aren't any catless, divorced style downpipes with 2 bungs already installed that juuuuust might be enough for me to go with the Invidia V2. I dunno.... I'm just really really anal about a shop welding in another bung. I want something that's good to go from the manufacturer.

Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #19 on: April 18, 2012, 11:08:59 PM »
Isn't the Invidia divorced? I am running the divorced Ividia because I got a great deal on it (thanks tank and Russ). Russ had to weld in a bung for my wbo2. I was previously running a belmouth ERZ catless.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com

Offline CornOntheCobb

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #20 on: April 19, 2012, 02:29:01 PM »
The Invidia V3 is divorced, the Invidia V2 is bellmouth. On a positive note, I found out the V3 is available with 2 bungs. Allllright!

Offline bspec

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Re: Need two o2 sensor bungs in the downpipe?
« Reply #21 on: April 20, 2012, 07:25:44 AM »
Thanks for the info and congrats on the find.
the bottom line is this, people just need to realize that when they buy cheap CO's [KW on down], they are buying cheap, poorly engineered shocks for the sake of having height adjust-ability. - whitetiger on legacygt.com