huh?

theres two sensors. 1 in the headers (02 AFR) and one in the exhaust.

MAF is completely different

i replaced the afr 02 sensor

I know that its jsut the price for such a little part that im looking at. Im talking about the 02 sensor in the dump pipe of the exhaust. I take it the headers one is more expensive?

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased

yeh the dump pipe is cheap, around 180, cheaper from USA.
or u can try wreckers. though i didnt think that the ecu depended on the rear 02 sensor much.

Well it doesnt seem to. I have driven it around yesterday with it disconnected and have 0 problems. However, problems dont usually occur till it has become a problem :P.

You can see all the richness on the 02 sensor of mine. Unlucky! ;/

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased

im pretty sure that gc8's only have one o2 sensor, it is only the newer wrx's that have 2 o2 sensors, but i think that one of them is a egt sensor? (the one before the turbo) and a 02 sensor down near the trans, after the main cat

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Version 6 STI

Stock Bugeye onwards have 1 oxygen sensor located in the headers, an exhaust gas temperature probe in the up-pipe and an additional oxygen sensor located after the cat-converter in the dump pipe , before the main catalytic converter.

Therefore:
2 x o2 sensors
&
1 x egt probe

Ok so my question originally is, will running my MY00 GC8 WRX without the 02 sensor located after the turbo on the dump pipe, lean my car out and kill something? To be honest im not sure if its because my car is so smooth now that i feel it to be a little less quick, or it actually lost power.

Could just be me being paranoid :P

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased

It wont cause your car to lean out, it will have no feedback control from the o2 sensor, so it will default to the factory cruise fuel maps.

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Version 6 STI

Your probably talking about the EGT probe in the up-pipe. 2.2k ohm resistor prevents a CEL occurring, by fooling the ECU into seeing a resistance within its operating range for that sensor.

As for the O2 sensor, it provides feedback for closed loop operation only. Because its a non-linear narrow band sensor (which is also the case for 99.9% of cars on the road), it really cant do much more than provide closed-loop feedback during over-run, cruise and also engine start.

Without the O2 sensor, the ECU stays in open loop...and generally, most cars run rich as a default when the O2 is fucked and/or missing, whether your cruising or going flat out.

So it will run rich till i replace my 02 sensor. Thanks for the helps guys. Its good to have a car that i can gentley warm up without it surging like a bull :P

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased