O2 Sensors

[FFRSpec72]

OK you Subaru guru's. I'm going to run 1 stock O2 sensor (the one on the stock exhaust on the passenger side of the exhaust under the engine), I need to get a new O2 sensor, so is this the upstream or downstream sensor that I need ? Also which plug in the picture goes to what O2 Sensor ? I will run a wide band O2 sensor after the turbo to monitor the AFR. I gather the engine will run fine with just the 1 factor sensor and I may have to disable it to prevent the CEL from going on.

57166

[Hindsight]

You want the upstream, aka Front o2 sensor.
Your connectors are different from mine so can't help you there. I would look at a wiring diagram.
I am not sure about the year you have but on mine, I had to disable the code AND edit a couple tables. On my year, the ECU adjusts fuel trims based on rear sensor signal under cruising conditions. Its easy to do via accessport, and possibly via open source.

[Bob_n_Cincy]

Tony
you can use wire colors to figure out which is which connector.
Bob
http://thefactoryfiveforum.com/attachment.php?attachmentid=57167&d=1470372129

[FFRSpec72]

You want the upstream, aka Front o2 sensor.
Your connectors are different from mine so can't help you there. I would look at a wiring diagram.
I am not sure about the year you have but on mine, I had to disable the code AND edit a couple tables. On my year, the ECU adjusts fuel trims based on rear sensor signal under cruising conditions. Its easy to do via accessport, and possibly via open source.

Figure as that is the more expensive one .... more $$$$

[FFRSpec72]

Tony
you can use wire colors to figure out which is which connector.
Bob
http://thefactoryfiveforum.com/attachment.php?attachmentid=57167&d=1470372129
Thanks got it !

[STiPWRD]

I'm pretty sure the internals of the O2 sensors are the same b/w upstream/downstream, they both produce a 0-1V analogue output. The only difference is the connector. I don't know why the upstream O2 sensors are so much more expensive but I've heard they go bad less often.

If an upstream sensor goes bad, I'll usually buy a downstream sensor (cheaper), cut the connector off the old one and solder it on the new one. I've done this on several different cars and not had an issue.

[Hindsight]

Oh wow, I always thought the front sensor was a wideband sensor and the rear was not?

[redfogo]

I'm pretty sure the internals of the O2 sensors are the same b/w upstream/downstream, they both produce a 0-1V analogue output. The only difference is the connector. I don't know why the upstream O2 sensors are so much more expensive but I've heard they go bad less often.

If an upstream sensor goes bad, I'll usually buy a downstream sensor (cheaper), cut the connector off the old one and solder it on the new one. I've done this on several different cars and not had an issue.

They are different one is wideband that's the more expensive upstream one and then you have the downstream one that a narrowband that's strictly for emissions. Your Wideband(upstream) O2 sensor is used so the ECU can read the AFR. Your narrow band can't really read AFR very well sense its reading spectrum is limited.

If you have a tactrix cable you can log your AFR although some will argue that the OEM sensor is a bit more limited compared to aftermarket widebands.

You can get a cheaper and just as good O2 upstream sensor if you buy a bosch plug much cheaper then the OEM Denso. Lots of guys are running the bosch option. I am as well no issues so far.

Also you can't delete the O2 on the 32bit ECUs. The 16bit ECUS don't care you just need to block the check engine light.

[STiPWRD]

They are different one is wideband that's the more expensive upstream one and then you have the downstream one that a narrowband that's strictly for emissions. Your Wideband(upstream) O2 sensor is used so the ECU can read the AFR. Your narrow band can't really read AFR very well sense its reading spectrum is limited.

You can get a cheaper and just as good O2 upstream sensor if you buy a bosch plug much cheaper then the OEM NGK(think its NGK). Lots of guys are running the bosch option. I am as well no issues so far.
What do you mean by wideband? The upstream and downstream stock o2 sensors both produce the same voltage output (0-1V). A wide band O2 produces 0-5V and covers a much wider range of AFR.

[redfogo]

What do you mean by wideband? The upstream and downstream stock o2 sensors both produce the same voltage output (0-1V). A wide band O2 produces 0-5V and covers a much wider range of AFR.

Hope this helps :) http://forums.nasioc.com/forums/showthread.php?t=1922848

[STiPWRD]

Hope this helps :) http://forums.nasioc.com/forums/showthread.php?t=1922848
That's an interesting read, thanks. There's a good bit of discussion and differing opinions going on in that thread. My take away is that the stock upstream o2 does have a greater AFR measurement range than the stock downstream o2 so they probably shouldn't be interchanged, at least on a performance car. Perhaps I got lucky on the few cars I've put in downstream sensors in upstream locations, as it hasn't had a noticeable effect. I'd still reserve the term wideband for a true 0-5V sensor though. One of the posters in that thread discussed his testing of a LC-1 wideband vs stock front O2 and found a noticeable difference:
http://www.iwsti.com/forums/ecu-tuning-and-performance-electronics/36914-stock-narrow-band-o2-vs-lc-1-wideband-o2-lots-data.html

[redfogo]

That's an interesting read, thanks. There's a good bit of discussion and differing opinions going on in that thread. My take away is that the stock upstream o2 does have a greater AFR measurement range than the stock downstream o2 so they probably shouldn't be interchanged, at least on a performance car. Perhaps I got lucky on the few cars I've put in downstream sensors in upstream locations, as it hasn't had a noticeable effect. I'd still reserve the term wideband for a true 0-5V sensor though. One of the posters in that thread discussed his testing of a LC-1 wideband vs stock front O2 and found a noticeable difference:
http://www.iwsti.com/forums/ecu-tuning-and-performance-electronics/36914-stock-narrow-band-o2-vs-lc-1-wideband-o2-lots-data.html

Yep not worth the risk if you dont have to take it for sure. I would not tune off of the OEM sensor some have but I rather just go off of a true wideband.

[FFRSpec72]

Thanks everyone for the great discussion and pointers !