O2 sensor location

[65 drop top]

I’m installing a Sniper efi on a bbc. Where is the best location for the O2 sensor? Would it be in the header collector or in the exhaust pipe after the header? Heres a picture of the same headers for reference. Thanks.

[CapSS92]

If you have long tube headers, mount the sensor approximately 1-10” after the collector. You may have to drill a hole in them pretty headers. Good luck amigo.

Alex

[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).

[Mr Nick]

In the collector, at least 10* rotated up from parallel to the ground. Grind off the ceramic coating, weld, and then touch up the area with ceramic header paint.

[65 drop top]

Thanks for the info, so pretty much where I circled is where I want the sensor? I’ll make sure to install it at the correct angle. Fortunately and unfortunately, I need to have the header recoated anyhow, so adding a bung in the header isn’t terrible.

[anguilla1980]

Personally, I have mine about 2" behind where you have circled. It's up on a 45 degree angle facing the top of the transmission. I wanted to make sure it was picking up after the point all primaries had mered so the gases from all 4 exhausts were thoroughly mixed. Modern o2 sensors are heated so I'm not worried about exhaust temp tooooo much, plus your headers are coated which holds heat in pretty good. Just never go too close to the H or X pipe.

[65 drop top]

Time to get out the drill, thanks for the info guys.