Wideband o2 question....
 

Hey guys,

I am right in the middle of buying, sourcing, and getting a game plan together for my EFI change over.

I am curious if anyone has experience with wideband oxygen sensors and where is the best place to install one on a short exhaust system.

I am going to run a 3" pipe off the turbo approximately 3" long into a 14" long straight through design magnaflow muffler and come out of it with a 3" pipe appromimately 12" long to exit out the right side of my car.

My question is this. I am curious if I should go before or after the turbo. If after how close to the turbo can I safely be or should I go after the muffer but right against it as to not have any outside air get sucked in and interfere with readings.

Your thoughts on this would be greatly appreciated. A good friend of mine Rob brought this up to me and I figured I would start a thread dedicated to this subject.

Please limit responses to people who actually have experience using wideband set ups and not "what ive heard". I think it will make for a much more accurate thread.

Thank you!:D

Gumba11-
there has been threads on this at Rennlist, but I remember it's AFTER the turbo, about 3" to let the turbulence settle and usually bunged in the 12 o'clock position.

I'm running a Magnaflow as well (the 3" I/O 6" dia tube). I believe that unit is about 18" long, but found it too loud for me. I doubled back under with a mini Borla XR1 tube rather than straight pipe and out the driver's side. now quieter, but much deeper than stock or a bypass. if your interested in pictures, they are on another earlier dated thread something about "does size matter". when dyno'd, the Magnaflow/Borla setup cost me 23hp compared to the Fabspeed single which was intolerably loud.

you should have enough room to place your O2 sensor correctly. before you do, do a search on the Rennlist Forum just to make sure if somebody else here on the Pelican board doesn't confirm me.

Gumba11-
wait a minute... aren't you the guy who started the "size matters" thread to begin with? never mind.

Hi Chris,
I know you said no "what you heard", but I read this online :)
Seriously though, Rudy911 was kind enough to post all this info that you need. He found he had to install the sensor after the muffler because it got too hot before it.
Hopefully he will advise you.
Placing too near the tip will give false results at or near idle. Place it directly after the muffler.

Thanks Nathan! Gino youre correct! :)

Nathan-
curious, and confirmation to that 'too hot' situation; although "what I've read/heard" is to the contrary. my wrench instructed me to put the bung in the 180o 1/2 donut return pipe in-between my 2 mufflers. I'm not running an O2 sensor, but he told me to do this for setting the CO% (3%). I guess if it's good enough for that setting, it's good enough for the wide-band extras goodies as well.

Is your technician using a "sniffer" or a sensor or probe of some kind. I am thinking it really doesnt matter where you check CO% as long as you are not too close to the end of the pipe.

I was told that wide band o2 sensors will not deal with heat like the older single wire units would.

I dont know if that is correct and this might even be the time to just open this up into a general conversation about anything and everything o2 related so we can learn more!!! :D

Keep the thoughts coming, this is good reading!

Chris, aren't you doing what you asked us not to do?:)

I have run a few different mufflers on my car. I have had the O2 sensor before and after the muffler. It made no difference. The O2 worked fine both places.

If I were you I would put the O2 sensor right after the turbo and run a 3" Borla XR1 muffler exiting stage right. I had a 12" one I think and it wasn't too loud. That is coming from a 49 year old fart. I built a small muffler for my wastegate outlet cause it was too loud.

The sensor should be installed post turbo. Mount it a few inches away from the turbo.

If mounted pre-turbo, not only can the temp affect the readings, the pressure affects the readings also. There is a Bosch white paper that has pressure correction cuves

:) http://forums.pelicanparts.com/uploa...1181018056.jpg

OK, I know I haven't done it, but I was very interested in what Rudy911 was doing/learning with his and I will not fit mine before the muffler.
He found that before the muffler (after turbo) the sensor got too hot causing an error code.

I have an extra complication of having a twin outlet muffler and we know that the sensor being too near the tip causes inaccuracy at low gas flow.

I have mine after the turbo and before the muffler. I have a LC-1 and have no problems w/the readings..(all accurate)..also have not had any problems w/the sensor getting too hot.

http://forums.pelicanparts.com/uploa...1181075356.jpg

LOL.

Be easier for me if I could get away with it inbetween the turbo and muffler.

How many miles have you used yours for Phil?

I have a straight pipe after the turbo and my LM-1 O2 sensor is ~5" after the turbo. Have accurate readings & no issues. And I have installed it for ~3 years now.

FYI

Part of a Bosch white paper regarding O2 sensors, section regarding effects of temperature and pressure on the sensor.



http://forums.pelicanparts.com/uploa...1181168702.jpg

l put my wideband probe right after the Powerhaus muffler,right where they placed the bung.You may be okay with mounting it after the turbo but the closer it gets to the flame the worse it is.Ever see flames come out of a turbo or zork tube? You don`t want the sensor to get that kind of heat. Read the instructions,excessive heat reduces sensor lifespan.

I have decided to put my sensor approx 6 inches after the turbo. I think it should work fine there as I have talked to many others who have done it in that location and have been running for over two years with no issues to date.

I will post if I experience otherwise. As for the flames, I think the temperature is very similar with or without flame. The turbo has to get heat soaked enough to induce that situation and at that point I dont think the flame would be an issue. Im no expert though. Just my opinion.

.................................................. .Chris:)

l think 6 inches is far enough away anyhow,best of luck with it

I've had flames shoot out about a foot behind the car. Should I put the bung 2 feet behind the car? :)

Seriously, I think it is roughly the same temperature with or without flames. Flames are more an indication of unburned fuel still being present.

Mine is before the turbo and it is not accurate. I need to move it. When my ECU was tuned they did not use my AFR meter. They mentioned to me that I should not trust it. I have often wondered why they just did not move it for me?