O2 sensor nut size??

[J.JohnsonLGT]

So basically I have a Cobb down pipe, and the o2 sensor is placed before the cat. I need to move that to after the cat, but I don't know what size nut I need to get to weld in place of it. Does anyone know what size I need?

[BarManBean]

It's probably M18x1.5. Just pick up a standard O2 bung. If you're not doing the welding yourself just tell the exhaust shop you need an extra O2 bung welded in.

 

WHY do you think you need to do this? Pretty sure that placing an O2 sensor just aft of a cat converter will cause wonky readings.

[J.JohnsonLGT]

I was told there should be an o2 sensor before and after the cat.

[BarManBean]

I was told there should be an o2 sensor before and after the cat.

 

By whom, and for what reason? If you add an extra O2 sensor, where do you plan on plugging it in?

 

If you are talking about adding a wideband O2 sensor along with a gauge and/or some sort of logging setup, you want the WBO2 to be before the cat converter.

[J.JohnsonLGT]

I'm not I was getting a code from the cat monitor and the guy said it's because there's no o2 sensor after the cat. I checked the cat its brand new basically. I'm just lost at what it could be