Q about placement of wideband A/F sensor

[richardholdener]

The position of the oxygen sensor in the exhaust system will not change the reading (rich or lean). The farther away from the cylinder head, the air/fuel curve will have basically a time lag when compred to engine speed. This means that the curve will be the same with respect to rich or lean, it will be just shifted slightly in the rpm range. Once agin, no change in air/fuel reading from change in position of oxygen sensor or from having catalytic converter in system (seems odd but back to back tests reveal identical air/fuel before and after cat).

Originally Posted by LtNoogie

I just wanted to get this straight in my head. The further back one places the wideband A/F sensor, in the exhaust system, the leaner it will show? i.e. most accurate is in the header, more lean after first cat, more lean after second cat.

The reason I ask is that when I dyno'd the car, the mechanic read the A/F mixture from the tailpipe. The entire A/F curve is probably shifted slightly to the lean side, right?

TIA