O2 sensor placement for exhaust

[Ace23]

What is the recommended placement for an O2 sensor in our side pipes? I'm upgrading to 3" exhaust and I would like to go ahead and have the bung for the 02 sensor installed. I currently have a carb on the car and I plan to install an A/F gauge. I've been told the sensor placement is critical in order to prevent moisture buildup on the sensor and inaccurate readings. Thanks in advance.

[eschaider]

The closer to the exhaust port the better, Ace. The greater the distance from the exhaust port, the later the ECU will see the change in oxygen content and the later it will adjust the fuel mixture. While many ECU's have an adjustment for the timing of the changes based on the location of the sensor the inescapable fact is the farther from the exhaust port, the greater the time delay before the ECU can respond and the more potential detonation damage you expose the engine to.

If the sensor is just for tuning purposes with a carb then the time delayed response is less meaningful because the carburetor does not possess the ability to manipulate the fuel delivery in real time like an ECU does. That said, you still want the sensor as close to the exhaust port as is practical with or without an ECU to minimize any backwash of ambient air that enters the exhaust system from the open collector, skewing the sensor reading towards the lean side of it's range.


Ed

[smallblockhead]

I just installed an Innovate Motorsports LC-2 Wide Band O2 sensor in my car, the OEM states that it needs to be placed a minimum of 24" from the exhaust port, preferably in or after the collector. A WB O2 sensor will be damaged at high heat (900 F).

Gary

[DonC]

The closer to the exhaust port the better.
To prevent moisture from damaging the sensor insure that it's mounted 90 deg or less to the vertical. Less than 90 deg will create a sump that will collect moisture and ruin the O2. Particularly if you're going with a wide band sensor.
DonC

[bobcowan]

After the collector merge is the best place, so you're sampling from the entire bank and not just on cylinder.

"Weld the bung at least 24 inches downstream of the exhaust port outlet
(after the collector), or 24 inches after the turbocharger if so equipped.
The bung should be welded before the X or H pipe if so equipped"

"Using a clock as reference, mount the bung between the 9:00 o’clock
and 3:00 o’clock position. Welding the bung in the lower section of the
exhaust pipe can result in sensor damage caused by condensation
making contact with the sensor’s internal heating element"

http://www.innovatemotorsports.com/s...LM2_Manual.pdf

see page 8

[lippy]

Mine is on the passenger side, on the sidepipe after the collector and before the muffler. If you are looking to the back of the car down the sidepipe, it's at approximately 4:30, which is as close to level/up as I could get it.

Even though I had already ceramic coated the pipes black, I ground off a small amount of ceramic and TIG welded the bung. I then masked it off and used VHT black spray paint on the bung and weld. You can't notice it.

[Wbulk]

O2 Sensor Install

[Ace23]

Thanks to everyone for their input. Given that I am looking at an innovate wideband I am going to lean towards their installation advice. With the new set of pipes I figured I should take the opportunity to go ahead and have the bung welded in. Should be interesting to see what kind of readings I get.....my car runs so well after the work that was put into last year.