Finn Lassen wrote:

Tracy has told me that 0.7 volts from the oxygen sensor is best power
mixture; more is rich and less is lean.

I've been seeing .8 to .9 volts and so decided to lean (drill the jets
smaller) the two outer carbs. Well, seems engine starts running more
rough, even when I still see .7 volts or more. EGT shoots up (saw as
much as 1,760F), cowling starts melting, etc.

Is it possible that the O2 sensor could fail in the direction of
indicating too rich when it's really lean?

Finn

Ed Anderson wrote:

 Finn,
    I did a bit of research on O2 sensor, when I designed and built my own
Air/Fuel (Lambda) indicator.  While these 02 sensor are similar they are not
identical between brands.  The sensor curve looks rather like a backwards
"Z" and the voltage curve on the tail end of the "Z" can vary a bit from in
different makes of sensors.  With the sensor I am using, the best power part
of the curve does not start until almost 900 millivolts (0.9 volts),
actually around 0.87 volts.  So 0.7 volts would be less than best power for
me, but would still be above strictrometric (sp?)  point which is approx 0
.45 volts.  So you should not be running "lean" at 0.7 volts.  0.7 volts
should represent something like "Power Cruise" - resonable power with
moderate fuel useage. However, while the center part of the "Z" sensor curve
is fairly straight and linear, the arms can be fairly non-linear, so a small
change in voltage can indicate a large change in A/F mixture.

  Having a mixture control with Tracy's EC2 makes it possible to change the
A/F mixture at the touch of a figure and note the change in voltage of the
O2 sensor (or in my case the LED lights).

The only failure modes I read about generally result in less output voltage
like getting clogged by lead ( if using Aviation gasoline) or apparently
they will deteriorate with long usage.

  I personally would tune my jets a little richer since you can't change it
in flight.  You might burn a little more fuel but that would be about the
worst of it.

FWIW

Best Regards

Ed

Ed Anderson

 
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