[eschaider]

It is just a square stainless block with the same bolt pattern and external dims as the SPF flange and fits between the header and the sidepipes. The entire center of the block is cut out to provide one large cavity. You need to move the header flange back on the header a distance equal to the thickness of the block you decide to use. Place your O2 bung in the block at 3,9,or 12 o'clock, wherever it works best for you.

Once the exhaust leaves the header pipe it enters the square cavity in your stainless block, between the header and the sidepipe flange, where I am sure there is a lot of mixing going on. The sensor detects and reports whatever O2 content it finds to your ECU for injector pulse width calculations to meet your target AFR. The exhaust gas exits through which ever side pipe tube it is nearest to. No fancy science here just a simple way to plumb an O2 sensor, keep it 12 to 18 inches from the exhaust port, protect it from road debris and positioned so as to minimize the condensation of water in the sensor after initial startup.


Ed