I have access to a wide-band O2 sensor for tuning. I was going to fab up a testing muffler from an old Bursch I have laying around, but it occurred to me that maybe I could make a tail pipe extension that would house the sensor. Maybe a 90 degree bend and then a 2' straight pipe with the sensor in the first 3"? Is it okay to test exhaust gas after the muffler? The wide-band O2 is heated, so that's not a problem.

I think it is supposed to be as close to the collector as possible to get accurate readings, at least that is what I have always been told. Not sure why, maybe because the heating element of the 02 sensor is only supposed to be for warmup and the exhaust heat is required for accurate readings during normal operations? Just a guess . . .

You're thinking narrow-band, which does need to be run hot, and as close to the collector (or, ideally, the port) as possible. With wide-band, it's not so much an issue, as it's temp is controlled much more closely.

Mark, one thing I've heard is an issue with tailpipe installations is getting outside air IN to the pipe at or near idle, diluting the exhaust gases. Once you're moving or have any real load on the engine, it's not an issue. After the muffler should be fine. One thing you do want to be absolutely sure of is all of the exhaust joints before that point seal properly.

No it wouldn't be good to put the sensor so close to where the tail pipe ends. I'm thinking that I'll put an extension on the pipe so that I don't have to modify/damage my muffler or exhaust system in any way. Something like this (gray is existing muffler, green is new removable extension, red is sensor):

mark, i think that would work...if you look at the web site for the reader, it shows a device they sell (expensive) that sticks into the tailpipe, I think your idea is perfect.

Marc, I agree....I just put mine in just after the the 4 tubes come together...It is located right next to the passenger side tranny mount. This is right before going into the Bursh glass pack....photos later...

Here's what I made. Got all the parts at my local NAPA, including the sensor bung.

Sensor protrusion.

Slides on my tail 2" tail pipe.

Like this.

Only one problem. It's just loose enough to flop around. I'm not sure of the best way to firmly make up the difference as well as avoid having ambient air sneak in. I tried using some fiberglass mat but it's not good enough. Idea #2 is to cut slits in the side and tighen it with a clamp. Hmmm.... Anyone else have a good idea?