Downstream O2 sensor, where to install it? Options

[bryanf]

My 1994 Celica ST (7A-FE) is now 25 years old so today's emissions test will be the last! Im celebrating with a new exhaust system.

I already got the eBay stainless header, which I plan to have ceramic coated. I would like to use an aftermarket cat.

Should I install the downstream O2 sensor before or after the cat? The guide shows installing it in the downpipe, but in this thread Box (where are you Box?) says to install it after the cat. And what if i don't use a cat?

I also wondered where to get the proper flange for the sensor.



This post has been edited by bryanf: Jul 14, 2024 - 11:08 AM

[bryanf]

I have two sensors and two cats. The first sensor was in the manifold, then the first cat in the bottom of the manifold, then the second (downstream) sensor was in the downpipe, in between the two cats. The second cat was in the tunnel. No sensor after the second cat.

I'd like to try using the non fouler with no cat but that won't work with the flange type O2 sensor. Should I make a sensor extender with a flange? How long should it be?

Would a setup like the howto produce a CEL?