O2 sensor placement

[lesingepsycho]

OK, I talked to a shop today about welding in an O2 bung. They made a big deal about the placement of the bung as in, how far beyond the manifold to place it. Anybody have any input on this? Do I just want to go as close as possible to the manifold or do I need to be a little further down stream? I know that too far down stream is bad but can you be too close? I'm hoping some of you EFI guys can chime in here too because this O2 will eventually be feeding info to my Megasquirt. Thanks in advance!

JACK

 

[Glen_B]

If you're going with Megasquirt eventually, you'll be using a wide-band O2 like the LC1. Its heated so it doesn't have to be super close.
Glen Byrns

 

[14dna]

I agree with Glen, if it is heated, put it where it can be reached easily. These things tend to start giving trouble and can be hard to remove if in the wrong place. So somewhere close to the curve of the exhaust by the bellhousing area.

Dave

 

[lesingepsycho]

What about going in through the wheel well?

JACK

 

[racingenglishcars]

I think that spot is probably good enough, except I would place it sticking backwards out of the pipe, so you can turn it with a wrench through the hole. It's usually difficult to use a socket on a sensor because they have the long wires attached.

We've been working with O2 sensors for our test engine and found that placement is critical if the gases are not mixed thoroughly. Also, too fast air flow over the sensor pushes the calibration out a bit. We have to have a shield to reduce the direct airflow. The sensor needs to be at a high temperature, and with cooling of the exhaust pipe placing the sensor further downstream requires insulation wrapping of the pipe to retain the heat.

 

[c5racer]

Hi Jack,

I placed mine here, It will be getting used heavily once I get the car out to play!

Bruce