O2 sensor location

[68Formula]

For best results, install within 2" of the collector merge. As a matter of fact, a lot of OEMs run shorty headers with the narrow band right at the collector. A couple of reasons for this:



First, it has to reach a minimum temperature (typically over 600F) to operate accurately. The second reason has to do with response-delay. If you're datalogging, you want the sensor to pick up the signal as close to the combustion event timing as possible. That way the reading point is showing true to the speed/load point being compared. In other words, by the time the exhaust pulses reach the sensor, you could be one combustion cycle set behind if it's too far downstream. At high rpm, there's only milliseconds between engine rotations. And long tube headers are already... well... very long.

And, the further you put it upstream from the header collector/exhaust pipe sealing joint, the less likely you'll get bad readings if there's a slight leak. (The extra oxygen would show up as a false lean condition, or maybe cause the values to bounce around intermittently).