Posted by Troy Rudolph on November 19, 2005 at 06:48:36 from 63.246.185.123
In Reply to: weird exhaust part posted by KenB on November 19, 2005 at 00:02:04:
It's a port to allow measurement of the C0 value. The service equipment sold by BMW to its dealers at that time was designed to hook up to it.
It's one of the reasons that some shops just can't tune a '79-'81 528i properly. The CO values quoted in the "big blue book" are based on the location of that port which is *before* the catalytic converter. The tailpipe sensors that most shops use measure the CO *after* the converter.