best placement for o2 sensors?

Oh my, I read an article on this in one of the magazines. I think I remember it saying to install the sensor in the collector(geez, getting old sucks). I gave my friend a copy of it as he was adding the sensor to his supercharged Porsche. On a side note, my GF's Honda has two sensors, one in the front and one in the back, why, I don't know.

Copy cat! Next you're gonna tell me it's a Phantom gauge!

You want to put them as close to (or into) the collector as possible. I didn't want to put them in the collector, so I mounted them in the pipe connecting to the headers, real close to the collector. Placement is especially important if you are using a 1 wire O2 sensor. The 1 wires use exhaust temp to heat the element. If the O2 doesn't get enough heat it will not read correctly. The 3 wire O2 sensors are less critical because they use a 12v source to heat them.
I ran the sender wire from each sensor to an on-off-on toggle switch so I could switch from bank to bank, or turn the dancing lights off all together.

2nd Mustang said:

On a side note, my GF's Honda has two sensors, one in the front and one in the back, why, I don't know.

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before the cat, and after the cat.

dont know about all honda's. but the obd2 civics had the cat cast into the exhaust manifold.