O2 sensor bias

[John Wickerham]

Larry,

>Do tell.How about a little info on how you did this, and what other "symptoms"
>you may have observed. Maybe the ECM is thinking that the combustion
>temps are too high (isn't the O2 sensor output affected by temps?), and
>opens the EGR more to try to lower it? How high were you able to bias
>the O2 before you ran into problems with the EGR? Thanks!Larry

Well, I was expecting that by adding 100 to 200 millivolts to the O2
voltage that I might be able to get a bit better mileage.  My intention
at the time was to also run water injection to prevent too much heat,
etc...

While testing it alone, however, I noticed that mileage did not change
at all over quite a bit of testing.  I cranked up the voltage to about
400 milivolts since the device did not seem to be effecting the way
the engine ran in any way.  Within a few minutes of driving, I got an
EGR fault code.  Checking out my Haynes manual revealed that the
computer had commanded more than a 50% duty cycle on the EGR valve,
and that wasn't allowed.

Upon lowering the voltage, the fault code went away.  I assume then that
with increasing O2 voltages (or resulting narrowed pulse widths on the
injectors) that the computer also calls for more EGR since the mix is
now leaner.

Just my guess as to what is happening, but I think the additional EGR
is preventing me from getting an advantage from the leaner mix.
By the way, you can get one of these devices from www.eagle-research.com.
Price is I thin is $49.95.

Hope this helps.
John Wickerham