Opinions for o2 sensor location!

stup · 03-15-2010, 02:42 PM

Doing a lot of fuel tuning work to a customers car(previously dyno'd near 450whp on cis) and installing an o2 sensor...The rear muffler appears modified for 2 tail pipes and not sure which brand??

Problem is i only have a 3 inch space before i enter the silencer box and i was informed by the customer that CO readings prior to me receiving car were somewhat different from each tailpipe!....

My opinion was to mount on the left hand pipe near exit of silencer box as i think it would probably get fried quickly just after the turbo before it enters the box..

Whats you guys opinions?

Although the weld looks pretty neat,this tail pipe may be added on to silencer box for cosmetic reasons????

And where i thought location may be best?

mark houghton · 03:02 PM

That's probably your best bet, though it's pretty close still to the turbo and may get fairly hot from radiant heat but most likely not hot enough to fry the sensor. You could also add a heat sink to it.
Your other option might be to intall the sensor in the oposite end exhaust pipe (passenger side), as close to the body of the muffler as possible to limit the affect of background ambient air affecting the reading. That's where I've installed my AFR gauge sensor and it seems to work fine.

JFairman · 03-15-2010, 03:32 PM

I put mine where the yellow dot is, it works good there.
Seen people put it a little farther down the pipe so it's in front of the turbo bearing housing and it worked there too.

Alot of it depends where you want to mount the controller if it's an LC-1 because the bosch wideband oxygen sensor wire is only so long.

gsmith660 · 03-15-2010, 05:47 PM

This is where the Innovate tech told me to put mine and use a 1 inch bung and also the heat wrap/shield.

DonE · 03-15-2010, 06:07 PM

Here is mine. Its about 3 in from the turbo, so no chance of ambient air backing into the pipe. Its been there for about 3 years now with no problems (Innovate system hooked up to my ECU). Hard to see, but its at the 12 o'clock position.

stup · 03-16-2010, 12:49 PM

Quote:

Originally Posted by DonE

Here is mine. Its about 3 in from the turbo, so no chance of ambient air backing into the pipe. Its been there for about 3 years now with no problems (Innovate system hooked up to my ECU). Hard to see, but its at the 12 o'clock position.

Thanks for responses so far!

Could be an option then if you have been using yours in so close a location to the turbo with no issues?

I roughly have the same 3 inch space where i could mount it as near to the silencer as possible,i am pretty sure that Zeitronix and innovate recommend at least 8 inch plus or so...Out of interest has anyone else had postive experiences with the same location as DonE?

jwasbury · 03-16-2010, 01:02 PM

Here's mine...also close to the turbo. Its been fine here for over a year including some very hot days (at last summer's turbopalooza track day at Carolina Motorsports Park was probably over 90 degrees ambient)

RarlyL8 · RarlyL8's Garage

All of my mufflers are produced with the O2 bung in the spot shown in Don's picture. I've have my O2 sensor in that spot for several years as well. You can use a heat sink if you think heat will be a problem.

JBL930 · 03-16-2010, 01:33 PM

The stock location for the pre-cat sensor on a 993tt is also very close to the turbo, i don't see a problem with it. I'd go with the way Don and Brian are saying, otherwise you'll have a job getting good readings at idle

stup · 03-16-2010, 02:12 PM

Ok thats me decided then as nobody has seen issues being so closely mounted to turbo,as we know limited space with 930s exhaust set up!.

mark houghton · 03-16-2010, 03:02 PM

Quote:

Originally Posted by JBL930

The stock location for the pre-cat sensor on a 993tt is also very close to the turbo, i don't see a problem with it. I'd go with the way Don and Brian are saying, otherwise you'll have a job getting good readings at idle

I disagree. My readings at idle are stable and accurate as far as I can tell. My sensor is buried about 11 inches back from the tip of the tail pipe around a curve. Even if it were off a little at idle, I couldn't care less since I'm much more interested in AFR's beyond idle when there's lots of exhaust velocity.

Now, if I were to install an O2 sensor that near to the tailpipe and expect it to accurately control a Lambda emissions system, then I might think differently.

Funny how there have been so many posts on this topic over the years, and it seems the verdict has now swung back to it being ok to mount sensors directly after the turbo. If I recall, anything much greater than 950 degrees F is the kiss of death for wideband sensors. Read Innovate's information on that.

stup · 03-16-2010, 03:16 PM

Personally i would have liked it somewhere in between my yellow mark in top pictures and where DonE and Brian have it however we dont have much of an option with the 930 configiration shown above.....unlike my 964 turbo with cat bypass,i have sensor mounted 10 inches after turbo which is ideal.

I wouldnt have thought it would have lasted so long this close to the turbo but looks like these are more robust than we think!.....You can always re-cal sensor with innovate or purchase spare to check figures against once in a while if supicious with readings.

JBL930 · 03-16-2010, 03:26 PM

If yours is 11 inches back and around a bend then i guess that's far enough. I've seen many sensors fitted just after the turbo, i'm told about 4 inches would be optimal, but i guess you just do what you can. If you go through a sensor every couple of years who cares? As long as it works well when it's working!
Me talking about the 993 sensors may be wrong anyway, as i think they are narrow band and maybe subject to different temp specs? But there are plenty of people with wide band sensors just after the turbos, and they have worked fine. I'd just run with it Stu, maybe think about a heat sink though

WinRice · 03-16-2010, 03:26 PM

Quote:

Originally Posted by stup

Out of interest has anyone else had postive experiences with the same location as DonE?

Same as DonE and 'J', mounted at the 12 o'clock position. Going on 4 years now.

mark houghton · 03-16-2010, 05:34 PM

Quote:

Originally Posted by JBL930

If yours is 11 inches back and around a bend then i guess that's far enough. I've seen many sensors fitted just after the turbo, i'm told about 4 inches would be optimal, but i guess you just do what you can. If you go through a sensor every couple of years who cares? As long as it works well when it's working!
Me talking about the 993 sensors may be wrong anyway, as i think they are narrow band and maybe subject to different temp specs? But there are plenty of people with wide band sensors just after the turbos, and they have worked fine. I'd just run with it Stu, maybe think about a heat sink though

That's cool. I stuck mine where it is because I just didn't want to risk it after hearing too many negative experiences. Guess that there are as many non-issue experieinces out there as well!

To your point....whatever works. I'm good with that always!

RarlyL8 · RarlyL8's Garage

Having the O2 sensor as close to the turbo as with my mufflers is not optimal for sensor life. I always suggest a heat sink for those who leave the O2 sensor in permanently, especially track cars. O2 heat sinks are not expensive and widly used in other applications. Mine has been in several years as well but the car sees no track time anymore so it is easy on the heat/sensor.

smurfbus · 08:34 PM

On my V-twin 1060cc bike it gets so hot (lots of sensor errors) I had to rig up a huge heat sink even at 10in from the exhaust port and there is no turbo so I would use a heat sink definately so close to the turbo. The older innovate firmvare version was not so critical of the extra heat so some have downgraded back to that older firmware. That means the readings are not so accurate than with the newer firmvare, but still more accurate than the competitors that have no correction over sensor life.

DonE · 03-17-2010, 06:47 PM

The O2 sensor can take a fair amount of heat, but as someone said, if you're concerned, make a heat sink. In a Bosch article I read a couple of years ago, an O2 sensor really doesn't start working well until exhaust gas temps hit 1000 degrees (heated units help get the temps up early for accurate readings). The heat from the turbo doesn't even get hot enough to burn the shrink wrap on the wiring, which is closer to the turbo than the actual unit.

87 930 · 87 930's Garage

Mine's in same location as DonE's, J's, and WinRice and I agree with Bodart's opinion. Mine's at 10:00 and I'm using Innovate's $90 heat sink. No probs after 3 years.

16Volt · 04-09-2014, 07:14 AM

Dredging this thread back from the grave since there is some good info here.

I have B&B headers and a B&B exhaust. The current O2 location is right before the turbo:

From what I am reading here the general consensus is that a WB O2 unit should be placed after the turbo. After doing some reading it seems that using the location before the turbo isnt going to work for a WB unit (most site back-pressure affecting the readings which makes sense). All the turbo cars I have owned/built always run the WB in the downpipe after the turbo as well.

So the next question is do I have the exhaust pulled and bung put in right before the muffler as Brian does or do I go for after the muffler in one of the tailpipes (likely driver-side).

As I understand it heat could be a problem with before the muffler and ambient air/moisture an issue in the tailpipe. Seems to me that running it before the muffler with a heatsink is the best option. What do you folks say?