AFR Gauge 02 Sensor Location

[Doppelganger]

So the research I've done on installing the O2 sensor in a down pipe requires it to be installed 16 to 36 inches down stream from turbo along with it being before any catalytic converter.

The main discussion topics I would like to discuss are listed below.

1) What is the best location to install an O2 Sensor before cat?

2) Can you place O2 Sensor after cat?

3) Is it OK to delete the stock O2 sensor in the down pipe and install the AFR O2 sensor in its location?

4) If your not suppose to install an 02 Sensor close to the turbo then why do so many of the leading manufacturers of down pipes weld a bung 3-8 inches down stream from the turbo?



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[Doppelganger]

So this is the reason I made this discussion. This is a pic of a maddad V2 catted down pipe which is a great down pipe. I'd like to keep it and run it with my FP Green HTZ.

The main issue I'm having is that the extra bung for additional O2 sensor is only a few inches down stream from the turbo.

The other issue is the length of the pipe before the gasses hit the cat is only about a foot to a foot and a half away from turbo. So if I wanted to install a new extra O2 bung before the cat it would be sitting rite next to the cat which I'm sure isn't the best location for it.

My other thought is deleting the stock 02 Sensor to install the new AFR gauge in that location but I'm not sure if that's optimal since that lower 02 Sensor probably still is good for the ECU to have.

My other thought is I can weld an additional 02 Sensor after the cat which would allow me to keep the stock O2 sensor but it will still be after the high flow cat so I'm a bit torn on what to do.

Any feed back on this subject would be greatly appreciated and thanks for your time.

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[Raven32]

After the cat would skew the AFR reading. This is because the cat actually heats up exhaust temps to burn off additional gases before it leaves the car. I remember reading somewhere that it's the bits that stick outside of the bung that actually end up failing due to excessive heat. Can't remember where I read that though though.


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[Doppelganger]

After the cat would skew the AFR reading. This is because the cat actually heats up exhaust temps to burn off additional gases before it leaves the car. I remember reading somewhere that it's the bits that stick outside of the bung that actually end up failing due to excessive heat. Can't remember where I read that though though.


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Yeah I might take the dp to a shop and have them cut the cat out and weld in another piece of pipe with a bung making it catless.

But why on earth do these companies put the extra bung so close to the turbo outlet if these O2 sensors get fried being too close to the turbo?

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[Raven32]

Yeah I might take the dp to a shop and have them cut the cat out and weld in another piece of pipe with a bung making it catless.

But why on earth do these companies put the extra bung so close to the turbo outlet if these O2 sensors get fried being too close to the turbo?

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If you find the answer please let me know.


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[Boogieman98]

Yeah I might take the dp to a shop and have them cut the cat out and weld in another piece of pipe with a bung making it catless.

But why on earth do these companies put the extra bung so close to the turbo outlet if these O2 sensors get fried being too close to the turbo?

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It is my understanding that they place it so close for Tuning not for longevity of the sensor. In my opinion if you have a cat go a few inches before. If no cat like me install it in the rear o2 section then you can hook it up so you are able to read it through the ecu. Anyway that is my two cents


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[HolyCrapItsFast]

Just after the turbo is the best place IMO.

If you think about it the stock O2 is in the collector of the header closer to the source of the exhaust gases, so why would after the turbo be worse for wear. That the sensor lasts longer far from the turbo is a myth. The closer you can get to the source of the exhaust gasses the better because of time. There are whole milliseconds between when the exhaust gasses are expelled from the cylinder too when AFR's are read by the ECU and then too when adjustments are finally made. You could be several engine cycles past when trying to compensate for fuel issues. You can graph this out from a log and compare the stock sensor with the wide band and you will see that they track each other but with a delay between them.

The only down side is the there are often flow issues where the AFR signal becomes unstable because a flow profile is not well establish just after the turbo, but I have yet to experience a big issue here.

 

[Doppelganger]

Just after the turbo is the best place IMO.

If you think about it the stock O2 is in the collector of the header closer to the source of the exhaust gases, so why would after the turbo be worse for wear. That the sensor lasts longer far from the turbo is a myth. The closer you can get to the source of the exhaust gasses the better because of time. There are whole milliseconds between when the exhaust gasses are expelled from the cylinder too when AFR's are read by the ECU and then too when adjustments are finally made. You could be several engine cycles past when trying to compensate for fuel issues. You can graph this out from a log and compare the stock sensor with the wide band and you will see that they track each other but with a delay between them.

The only down side is the there are often flow issues where the AFR signal becomes unstable because a flow profile is not well establish just after the turbo, but I have yet to experience a big issue here.

Thanks for the info George I'm happy I don't have to modify my down pipe now.

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