Correct AFR, where to install the bung for wideband sensor?
 

HI, am getting ready to tune three MFI cars, I was thinking about installing the wideband bung in the middle of the muffler, rearwards to the engine.

I have seen them installed just after the three pipes come together in the headers but I wanted to have one fixed metering position and its alot easier to install (mild steel) there.

The MFI have no individual cylinder adjustment (what I know)..

If I position the bung in the lower section in the middle between the inlet pipes, would not that give a good reading?

http://forums.pelicanparts.com/uploa...1240095881.jpg

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Steve Wong may have a comment on where wb sensors should go.

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My $.02 is to install it so the sensor tip is facing down into the exhaust stream just aft of the collector on the header, or on a collector for all 6 cylinders, but upstream of a muffler, cat, or other device that divides or alters exhaust gas. The back side of the sensor needs to sample ambient air.

I installed mine on the tail pipe close to the muffler at approximately a 3 o'clock position on my carburated 71T (2 in 1 out). Seems to work fine.

Install it after the collector but before the muffler. If you are concerned about L and R cylinder banks being different put a bung in each one .

I would like to do an easy install, do not want to take down the SSI's.

If the original muffler is built like the Dansk muffler there are at least two positions that should be in the exhaust stream and far from the muffler tip to ensure steady measurements in the whole rpm band.
http://forums.pelicanparts.com/uploa...1297970910.jpg

I use the Innovative LM2 for tuning and perhaps install their new MTX dial-kit as a hidden permanent install in my 74 carrera (RS 2.7 MFI), the 70S and 69E are not being pushed too hard so I will only use the LM2 while tuning but the bungs will be installed for current and future adjustements.
http://www.innovatemotorsports.com/p...XL_Blk_Blk.jpg
MTX-L Wideband O2 Digital Air/fuel Ratio Gauge

Looking at it perhaps my "second choice" is better with fumes more or less going direct at the sensor. I will have to check access though..

http://i412.photobucket.com/albums/p...el/sptmuff.jpg

Bung Location
 

I mounted mine in the exhaust after the muffler. This isn't a picture of mine (I think I got it off of a different thread on this message board). I had mine welded at about 10 O'clock rather than 9 O'clock as shown here. I seem to remember you want it pointing down to avoid condensation forming on the sensor. If you don't like that solution, I've another picture I downloaded that will give you other ideas. Credit to the photos from past posters on this forum (sorry, I don't remember exactly who originally posted them).

Dave

http://forums.pelicanparts.com/uploa...1297973229.jpg
http://forums.pelicanparts.com/uploa...1297973253.jpg

Your planned installation on the bottom of the muffler will not last to long. When the sensor is mounted upside down condensation will collect on it a damage the sensor and give you false readings. From what I remember about the proper placement, keeping the sensor between a 9:00 to 3:00 clock position is recommended.

With heat exchangers, install where the pipes merge and collect. Install the bung so the mounting angle is as described below.

From one manufacturer (AEM):
"Mount the O2 sensor in the exhaust system at least 18 inches downstream from the exhaust port. If you anticipate high EGT's (over 800C), run a turbocharger, run at high RPM for extended periods of time or plan on running leaded race fuel then you must mount the sensor at least 36 inches or more downstream of the exhaust port as all of these can cause the sensor to overheat. On turbocharged engines the UEGO sensor must be installed after the turbo charger, if not, the pressure differential will greatly affect the accuracy of the unit. For accurate readings, the sensor must be mounted before catalytic converters and/or auxiliary air pumps. To prevent collection of liquids between the sensor housing and sensor element during the cold start phase, the installation angle should be inclined at least 10° from horizontal with the electrical connection upwards."

Sherwood

Thanks, learnt something new today, thats the beauty with pelican :)

I am now considering the opposite end of the tail pipe and make sure its gets the correct position. (second option)

Before the CAT obviously, if you still have one.

My thoughts as well. And I would add that after a bit of research, I understand our rear-engine design with basically short runs from the exhaust port->collector->muffler->tail-pipe, means that the o2 sensor will not likely see any difference in AFR based on placement. I hashed over this with the innovate folks and the good people on this forum and others. So my approach will be to weld the bung in a location that is easy to access and will extend the life of the o2 sensor. For now, I use the tail-pipe clamp with good results.

I am going to weld in a bung on the right side of the muffler, try to get 10-11 o'clock (30 degrees) angle.

It seems like the 911 mufflers channel the exhaust gas from the inlet holes, through the mid section and into the opposite side of the exhaust tip.
The only concern is routing the cable, could have been somewhat better but I am not going to weld up before I have tried a mockup.

(btw, not my pix, I just cropped and added, credit to the photographers!)
http://forums.pelicanparts.com/uploa...1298046051.jpg

How did this work out for you? How do you like the innovate???

I finally got this installed.

I went with this install, the MFI does not adjust the cylinder banks individually so this was the easiest install.
http://i412.photobucket.com/albums/p...a/DSCN1711.jpg
Routed along the driver side, and split the throttle bellow and pulled cable through, lots of room and strapped it up and away.
http://i412.photobucket.com/albums/p...a/DSCN1712.jpg

http://i412.photobucket.com/albums/p...a/DSCN1713.jpg

Installed the gauge in a homemade bracket where the ashtray usually would sit. Both earth and 12V+ easily available. Breaking in the engine so redline 5000 rpm for another 500 miles.
http://i412.photobucket.com/albums/p...a/DSCN1715.jpg

Tomorrow I'll bring my MFI tools and hit the road.