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Wideband o2 placement? Cant find answer

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ryno

15+ Year Contributor
205
3
Nov 1, 2005
boise, Idaho
Ive searched and read.....people have said the rear o2 location is fine to put the new wideband sensor in. Im running 3" straight pipe, so no CAT. But my concern is i have a after market thermal r&d exhaust, so the palcement may be too far away, then where the stock rear o2 would have sat. I measured and my rear o2 bung is appox 60" away from the turbo flange. Is this too far away too get any sort of accurate readings?


Im getting a fine read while cruizing(if the gauge is reading right) it is getting a 14:7, but at WOT im getting a 10:1. Im hoping the gauge is not going have to be moved and im running rich as s**t on WOT.
thanks

*edit*...it is a AEM UEGO wideband
 
The placement is NOT TOO FAR AWAY. The directions say 36" or more away from turbo.........the stock rear o2 will be fine, and you will get the same readings. The sensor will last longer due to the decreased temps as well......

Nice looking car and set-up by the way!
 
Thanks for the help and nice words! Now i just need to figure out how to use this dumb safc a little more, i feel like a noob all over again...:(
 
The placement is NOT TOO FAR AWAY. The directions say 36" or more away from turbo.........the stock rear o2 will be fine, and you will get the same readings. The sensor will last longer due to the decreased temps as well......

Nice looking car and set-up by the way!

This must fluctuate from sensor to sensor . . . the Zeitronix ZT-2 recommends at LEAST 16" away from the turbo. Personally I welded a bung into my down pipe and everything is fine. The further downstream the sensor is placed, the more 'lag' you may experience with the resulting signal. Also, the further downstream it is placed, the more susceptible it will be to exhaust leaks.

As mine sits now, I only have to worry about
*Head-Manifold
*Manifold-Turbo
*Turbo-O2 housing
*O2 housing-down pipe

Put it further back and you can add on Test pipe / Cat . . .


I'm also not too sure how the CAT would affect the WB readings. . .
 
The lag by placing the WB a couple feet further away will be very minimal & shouldn't worry about it. The WB has its own heater built into the sensor, which is why it can be placed further away. As for exhaust leaks, to my knowledge they shouldn't effect your WB WOT values (which is where it counts) as the exhaust will have pressurized exhaust flow, so while you may leak some exhaust out, it won't let outside air in to effect readings.

To the OP, what you described in your first post with ~14.7 at cruise but 10.0 at WOT is perfectly normal & what you should be reading. From factory the desired air/fuel ratio on a WOT pull is right around 9.5 to 1 (varies abit depending on rpm). Most WB's min reading is 10.0, probably why this is what yours is showing. Like was said most try to aim for around 11 to 1 on pump, so the tune is on the safer side. Use you logger & see what your car likes to run at for air/fuel as some like it abit richer. Air/fuel ratio makes the smallest impact on performance vs timing & boost (in most cases) so its usually better to run abit richer & be able to run more boost or more timing.
 
To summarize,

You want to put it as close as possible without putting it too close so the sensor wears down over time from heat.

The closer you put it, the faster the reaction time (not a big issue), but also the reading is more accurate because of possible exhaust leaks diluting the air stream.

I've found the best location is right after the flex section. Easy to run the wires directly into the cabin, and. not too far where there are many exhaust leaks (only 2 gaskets, turbo to 02, o2 to downpipe).

More than anything you have to make sure you don't have exhaust leaks before the wideband 02 sensor.
 
The lag by placing the WB a couple feet further away will be very minimal & shouldn't worry about it. The WB has its own heater built into the sensor, which is why it can be placed further away. As for exhaust leaks, to my knowledge they shouldn't effect your WB WOT values (which is where it counts) as the exhaust will have pressurized exhaust flow, so while you may leak some exhaust out, it won't let outside air in to effect readings.
Daren, exhaust leaks does in fact changes the WB reading. During WOT, flowing exhaust will create suction around the leaks and introduce ambient air into the system resulting in leaner WB readings.
 
I can attest to that. I had my wbo2 sensor just before mymuffler. I figured the farther away teh better for the life of the turbo. Especially since I'm using my wb o2 to give feed back to my ecu in closed loop (narrow band simulation).

My WB02 Saga:

I got an exhaust leak just after my o2 housing and I read bloody lean as he!! at WOT. As soon as I discovered and remedied the leak, I was reading rich (I attempted to tune the rich reading out).

Also, I couldn't get my long term fuel trims to settle. It took Thomas and Dave of ECMtuning to figure this out. But Dave finally mentioned, "you're o2 cycling is 'sluggish'. Once I moved my o2 sensor to the stock location my fuel trims cleared up.

THEN, I got a REALLY, really lean reading when going WOT. I tried to tune it out. I have pleny of pump. My AFPR functions properly. I have no fuel leaks. Etc. I moved my o2 sensor about 20" inches down the exhaust from the stock narrow band location. Now it reads fine.

Placement is critical.
 
To clear my post up,
I never stated that further placement was better, but it works. I agree that the best placement would be near the end of the downpipe, right before the cat/straight pipe, which is somewhere close to 36"....
 
I got an exhaust leak just after my o2 housing and I read bloody lean as he!! at WOT. As soon as I discovered and remedied the leak, I was reading rich (I attempted to tune the rich reading out).

How lean did it show you were running? I just installed my AEM WBO2 last week and it's showing lean at WOT. 650cc injectors at -33% and 6gph MeOH injection and I should be rich as hell. The WBO2 is showing anywhere from 11.7: to 12.5:1 depending on what gear I'm in. OMG

I'm going to a friend's garage tonight to see if I can pin down a leak.
 
My sensor is mounted after the flex section between the firewall and block, with a fairly large leak at O2 to downpipe flange, I was reading 16-18 :1 at idle and about high 12's under WOT. Yes I freaked out initially as well. :)
 
Daren, exhaust leaks does in fact changes the WB reading. During WOT, flowing exhaust will create suction around the leaks and introduce ambient air into the system resulting in leaner WB readings.

Hmmm, this is strange. I could see a vacuum being created by leaks if the exhaust pressure was low enough, but I figured there would be more then enough pressure to overcome this issue. My WB sensor is mounted after the DP flex section & I ran it one summer with a large hole where the inner portion of the flex section was coming apart & it appears that over time the whole inner had seperated in the flex section & only the mesh overbraid was holding it together. My WB readings weren't strange with this & they didn't change enough for me to take notice after I replaced the flex section :confused: .
 
Hmmm, this is strange. I could see a vacuum being created by leaks if the exhaust pressure was low enough, but I figured there would be more then enough pressure to overcome this issue. My WB sensor is mounted after the DP flex section & I ran it one summer with a large hole where the inner portion of the flex section was coming apart & it appears that over time the whole inner had seperated in the flex section & only the mesh overbraid was holding it together. My WB readings weren't strange with this & they didn't change enough for me to take notice after I replaced the flex section :confused: .
I seriously doubt that there are much, if any, exhaust pressure present after the turbine housing considering most of us has 3"+ free flowing exhaust. Instead, hot gases are flowing so fast that it creates a suction effect around the leaks, this is how a "crankcase exhaust scavenging systems" work. I can't explain why your exhaust leak didn't create a significant change in your wideband readings because it certainly did with my situation. This is also a known issue, post a thread on any of the vendor support sites about why your brand new wideband is reading extremely lean and first response will most likely be "check for pre-sensor exhaust leaks".
 
Well, I might have pinned down my problem. We threw the car up on the lift and much to my suprise, my friend has a smoke machine!!!! :)

Turns out the flex section is leaking. I would have never expected that, since the DP is only about 2 years old and probably only has about 1500 miles on it. :( I guess the other option would be to plug the bung behind the flex section and weld in another one in front of the flex section. I'm just not sure if I want to spend another $300 this year on the Spyder. The wife is already a little ticked at all the money I've thrown into it this year.

I also found out that apparently when I had the turbo installed, someone snapped one of the studs off of the manifold and didn't bother to tell me. The smoke test didn't show any leakage there, so I don't know if it's worth all the time it would take to fix the broken stud???? All the other studs are tight and accounted for.

It didn't look like a huge leak, but I guess pumping smoke in the exhaust under very minimal pressure at the tailpipe wouldn't provide an adequate representation of the size of the leak. If it's not the leak causing the problem, then the only other possibility would be a problem with the FPR. I'm leaning towards the exhaust leak only because I don't recall reading about anyone encountering a faulty FPR.
 
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