Wideband placement

[GCubersoldat]

Upgrading the basically useless narrowband i have for a wideband AFR gauge soon and i was curious as to if i could simply disconnect one of the rear O2 sensors and put the wideband O2 sensor in its place. I have longtubes and an O/R X pipe so the AFR readings wouldnt be affected i would assume?

The rear O2 sensors are turned off in the tune i currently have, so it wouldnt be causing the ECU to go crazy. Wanted to see if anyone else has done this in the past.

 

[antcjr]

This is how my wideband sensor is setup. In my situation it does not affect the readings. At WOT I'm in the 11s and idle in the 14s.

 

[redfire04gt]

I had a bung welded on my o/r x just a couple inches after the collector on the header. Ideally it would be closer than the rear 02 location. I would recommend following the directions of the wideband you buy. Usually the sensors should be mounted at an angle as well.

 

[2001cobravert]

Putting it in place of a rear o2 is way too far back. My friends with long tubes put a bung in the collector. That or a little after the mid-pipe flange.

 

[troymach1one]

I did mine about 6" from header collector at an angle. I am using a dual wideband FAST.

 

[GCubersoldat]

Hmmm. What is the variation in reading from having it at the collector vs. A rear O2 slot? A whole point or 0.1-0.2?

 

[encasedmetal]

Hmmm. What is the variation in reading from having it at the collector vs. A rear O2 slot? A whole point or 0.1-0.2?

probably jackshit. and since your car isn't running in closed loop at WOT it doesn't matter really. just compare your wideband reading to the one your dyno uses and just make note of the difference. for instance- when tuning for longtube headers you are compensating for the longer distance in the tube itself and telling the ecu that it will take longer for the reading to transfer back. it's a delay factor.

 

[GCubersoldat]

probably jackshit. and since your car isn't running in closed loop at WOT it doesn't matter really. just compare your wideband reading to the one your dyno uses and just make note of the difference. for instance- when tuning for longtube headers you are compensating for the longer distance in the tube itself and telling the ecu that it will take longer for the reading to transfer back. it's a delay factor.

i see. Iv'e had my car on two different dyno's..one of the tuners used the rear O2 sensor hole and the other put the sniffer right on the inside of the exhaust tip. i cant see how the AFR reading would differ from collector to the rear O2 port considering its a straight pipe with no muffler or cats between the two...

Regardless, i ended up getting the innovate LC-1 with the bosch O2 sensor and it gets here today, will install, post pics, and compare the AFR reading of the sensor vs. the one at the dyno.

 

[flowgoode]

I have a PLX wideband set up and I had a bung welded in the X pipe right after the bend down from the stock exhaust manifolds. PLX recommended the placement be atleast 24" for N/A to 36" for turbo, downstream from the motor, so that's what I shot for. So I'm guessing that further down the exhaust wouldn't matter too much as long as there are no catalytic converters before it.

for instance- when tuning for longtube headers you are compensating for the longer distance in the tube itself and telling the ecu that it will take longer for the reading to transfer back. it's a delay factor.

To add to this, the front o2's rely on exhaust heat to supplement them since the o2's have a heater built into them. The ECU knows the "distance" from the motor where the front o2's are, so the ECU will eventually learn the delay within limits. But changes in the tune can help this along better.

 

[Brutal Metal]

I have a PLX wideband set up and I had a bung welded in the X pipe right after the bend down from the stock exhaust manifolds.

This is where mine is..

 

[Yellow98SVT]

The tuner who did my wideband install was an import guy, but, he knew his business. He told me that by placing the sensor in the rear o2's it would cause it to read a bit off...between .2 and .5. He said it would be lean by that much, however, because it was reading lean it essentially just gave me a small safety margin. If my wideband ever read at 12.0 to 1...I would get out of it. That being said, a 12 to 1 reading is in reality between 11.5 to 11.8 to 1, in my car.

 

[Myzticsnake]

Just last friday i tested this on the dyno. My wideband placed in the rear 02 slot was .1 different compared to the dyno oxygen sensor.

 

[GCubersoldat]

Just last friday i tested this on the dyno. My wideband placed in the rear 02 slot was .1 different compared to the dyno oxygen sensor.

thats what i was hoping for, exhaust gasses dont have anywhere to escape so the same ones that go through an O2 sensor at the collector vs. one at the rear O2 bung would be the same.

AFR's for me seem to be accurate w/ the one the dyno uses. mine was reading 12.6 at WOT and the dyno was reading 12.5, i can live with that :shrug:

 

[Myzticsnake]

thats what i was hoping for, exhaust gasses dont have anywhere to escape so the same ones that go through an O2 sensor at the collector vs. one at the rear O2 bung would be the same.

AFR's for me seem to be accurate w/ the one the dyno uses. mine was reading 12.6 at WOT and the dyno was reading 12.5, i can live with that :shrug:

Only reason I would consider moving it up the exhaust would be to get a faster reading of the AFR to know just a fraction sooner to get out of the gas if you tilt lean.

Considering the speed the exhaust will be traveling at high rpms, I highly doubt moving it 2 feet forward would respond quick enough to make a difference though.

 

[Justin@VMP]

I have taken lab grade NTK sensors with my AFM1000 widebands and put them in different places in the exhaust to measure A/F simultaneously. There is really no shift in a/f reading, only a delay and smoothing effect if you put it farther back or after a cat.

Cats essentially don't work at WOT, they just introduce a little bit of oxygen (which shows a leaner a/f) for a few seconds and then clear out. In some cases its better to get a reading after the cat, as high backpressure before the cat can shift the a/f reading by as much as .5, a stock GT500 has 15psi of backpressure and that is enough to shift the reading.

IMO the rumor of widebands reading leaner in the tailpipe or after cats started because of dynojet vacuum pumps with leaks in the tubing and worn out sensors.

 

[gnatsumarboc03]

I just stuck mine in the rear o2 spot.

 

[98KBCobraVert]

I have taken lab grade NTK sensors with my AFM1000 widebands and put them in different places in the exhaust to measure A/F simultaneously. There is really no shift in a/f reading, only a delay and smoothing effect if you put it farther back or after a cat.

Cats essentially don't work at WOT, they just introduce a little bit of oxygen (which shows a leaner a/f) for a few seconds and then clear out. In some cases its better to get a reading after the cat, as high backpressure before the cat can shift the a/f reading by as much as .5, a stock GT500 has 15psi of backpressure and that is enough to shift the reading.

IMO the rumor of widebands reading leaner in the tailpipe or after cats started because of dynojet vacuum pumps with leaks in the tubing and worn out sensors.

So in other words it's ok to put it in the rear O2 sensor bung?

 

[Justin@VMP]

Yep