Results 1 to 7 of 7
  1. #1
    Join Date
    Sep 2010
    Location
    Orange County, CA
    Posts
    485

    O2 sensor location

    Iím 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.
    Attached Images Attached Images  

  2. #2
    Join Date
    Jul 2006
    Location
    El Paso, Texas
    Posts
    330
    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

  3. #3
    Join Date
    Oct 2004
    Posts
    2,292
    Country Flag: United States
    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).
    Red Forman: "The Mustang's front end is problematic; get yourself a Firebird."

  4. #4
    Join Date
    Feb 2007
    Location
    Joliet, IL
    Posts
    1,014
    Country Flag: United States
    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.

    Nick ~
    1969 Cutlass

  5. #5
    Join Date
    Sep 2010
    Location
    Orange County, CA
    Posts
    485
    Thanks for the info, so pretty much where I circled is where I want the sensor? Iíll 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 isnít terrible.
    Attached Images Attached Images  

  6. #6
    Join Date
    Sep 2016
    Location
    Bakersfield, CA
    Posts
    265
    Country Flag: United States
    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.
    http://www.TheFOAT.com/92GTA
    1969 Pontiac Firebird
    w/BP 461ci stroker kit, 670 heads & XE274H cam. Primer black w/black interior.
    1992 Pontiac Trans Am GTA w/SLP Performance Package. Dark Jade Grey Metallic, grey leather, T-Tops.

  7. #7
    Join Date
    Sep 2010
    Location
    Orange County, CA
    Posts
    485
    Time to get out the drill, thanks for the info guys.