Re: O2 Sensors

[Frank Deutschmann <fhd@interport.net>]

PDQSHIP@aol.com sez:
> 
> O2 sensors in the audis changed from 2 wire to 3 wire in 1986(?)...  This
> move ios to heat the O2 sensor to its proper operating temp b4 the manifold
> does (about 600-650degrees).  This move also permits the mounting of the O2
> downstream of the very hot manifold (BMW mounts the O2 right in the front of
> the cat on my friends 87 635).  The object, beyond heat control, is that the
> O2 sensor last longer away from the high heat cycle components (read turbo
> man gets into the 1600-1900range).  The heated O2's are simple to upgrade to,
> and many race modified turbos go to them to make them last longer (did it on
> a race scirocco and a race spec GLH turbo in past lives). a quick weld of a
> nut to the exhaust (18X125mm) and a 12v source will do...

Hmmm.  I thought that the heated O2 sensors (three wire) were effectively the
result of an EPA campaign to reduce emmissions at cold start.  (The O2 sensors
must be hot to function properly, and heating simply via exhaust heat takes
time, during which the car polutes -- or so says the EPA.)

-frank
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