O2 sensor Voltage

[Chad Beauregard]

>"Steve Leonard" <gsxr1300 at hotmail.com> asked:
>
>>  I need to alter the voltage signal coming from a O2 sensor. I want
>to fool the ECU into a leaner condition.
>>  I am going to school, driving 110mi round trip. I want to see how
>much fuel mileage I can sqeeze out of my Geo Metro. Where can I get plans
>for a simple voltage "stepper".
>
>Uh, what's a 'Voltage "stepper"'?
>
>A simple single-supply operational amplifier could add an offset Voltage to
>the EGO Voltage, or could effect the EGO Voltage by a ratio.  "How lean can
>you go", we wonder?
>
>Mike


    "How lean can you go" is a good question.  Keep in mind that the leaner
you run an engine, the hotter it runs.  This could present a few other
problems that would make the mile or two extra mileage not worthwhile.
    I'm working on a similar project, only I want to be able to fool the O2
sensor in either direction (rich or lean).  I'll be using a microprocessor
to control the O2 sensor line to the ECU, and I'd like to be able to set the
conditions for rich, lean, and optimal mixture.  In my case, the ECU really
only pays attention to the O2 sensor signal from idle to about 3000 RPM,
depending on the throttle position.  I want to be able to fool the ECU into
thinking that the mixture is optimal during these conditions while I mess
around with the pulse width being delivered to the injectors.  My first idea
is to use an A/D to monitor the input voltage, modify it to optimal, and
then a D/A to tell the ECU not to change the fuel.  Any other ideas or extra
input would be appreciated.

 Chad

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