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Posted by: Porschef Aug 30 2014, 01:25 PM

My AFR gauge arrived yesterday and I was all amped to install it today. A few weeks back when I installed the sway bars I welded in a bung for the O2 sensor in the stock Leistritz muffler in anticipation of this day, however, it appears I may haven't enough room to install the sensor without cutting sheet metal.

Ain't gonna do that. The kit includes a bung so I'll just abandon the prior unit with it's plug, and weld in the new one (Oh Paul, where art thou ;-)

Question is, where? I know it's gotta be between the 9:00 and 3:00 positions, but would it behoove me to place it near the exhaust tip, or is anywhere else ok?

Anyone face this dilemma?



Thanks,

Joe

Posted by: Harpo Aug 30 2014, 02:03 PM

Racer Chris put my O2 bung on the headers just before the muffler.

David

Posted by: Mike Bellis Aug 30 2014, 03:07 PM

If it is a heated wide band, it can go near the tip. If it is a non heated narrow band, it need to go closer to the heat source.

Posted by: tomrev Aug 30 2014, 03:22 PM

I think for a meaningful measurement, it needs to be closer to the ports. Ideally in the collector for the bank. The muffler, or muffler tip will have too much oxygen not related to combustion, and give you a very inaccurate #.

Posted by: Porschef Aug 30 2014, 03:56 PM

It's a heated wide band. If it has to go in the muffler to allow both banks to provide exhaust, should it go near the outlet, or does it not matter?

Posted by: Mike Bellis Aug 30 2014, 04:37 PM

Heated wide bands will start to fail if the temp around the sensor stays above 800°F all the time. They sell a copper heat sink for these to dissipate the heat. You could build one yourself with 1/16" copper plate. They mount like a large washer between the sensor and bung. Aluminum will not work as well because unlike copper, it will not draw heat (conduct) as well. An aluminum heat sink would cool down fine but not draw the heat from the sensor.

A non heated needs to go closer to the head in order to heat up. Once hot they read the NB pretty well. Most installation instructions state to mount the sensor close to the head. In a T4, most mount on the header collector for best cylinder (4) reading.

On a heated wide band, You can mount it near the tip but as said above, it can read the atmosphere if too close to the end. In this case, as close to the muffler, on the lip elbow would be best.

Most dyno tuners use a tailpipe wide band for tuning. It inserts into the tail pipe 6". So I would use that measurement as a minimum from the end of the tip.

Posted by: Porschef Aug 30 2014, 05:27 PM

Thanks Mike and all, it is a wide band.

I'll try the end opposite the tip. Now to drop and weld...

Posted by: worn Aug 30 2014, 07:40 PM

I had the same problem replacing exhausts. Get the two things together and mock up. If it isheated, you can be down the line farther. As indicated above if you are out at the exhaust tip you are reading o2 from the air, but you need to be pretty close to the end if the line if you have gases flowing. Get you angle set and room for the wires and bungholio to your hearts content, and I hope that you do. Good luck.