DIY-WB bar graph display

[Timothy J Burgess]

Brian,

The circuit I described below has a mux (multiplexer) that selects the
scaled WB sensor output for the ECM O2 sensor analog input @ WOT, while the
NB O2 sensor input is selected @ part throttle.  An ECM that does not run
closed loop @ WOT disregards the O2 sensor input @ WOT, so the voltage
applied to that input my be any value, within the range of the A to D, as
it is basically being used as a data logging input @ WOT.

Tim Burgess


Date: Wed, 19 Sep 2001 13:03:26 -0400
From: Brian Renegar <thomas.renegar at nist.gov>
Subject: Re: DIY-WB bar graph display

If your using the WB as O2 input to your ECM, did you also flip the voltage
"direction"?  Narrow band O2's increase in voltage with richening mixture.
But the DIY-WB is just the opposite.  That could cause some MAJOR
problems!!


>I designed a level shifting stage that puts the WB circuit output in the 0
>to 1 volt range when its output is in the range of 1.4 to 2.4 volts, which
>corresponds to 10:1 to 14:1, and a mux to select either the NB sensor
>output (at part throttle) or the level shifted WB sensor output (at WOT)
as
>the ECM O2 sensor input.  This allows the use of a Diacom, Autoxray, etc.
>to log the WB O2 output @ WOT, in the range of interest.
-
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