O2 voltz

[G. Scott Ponton]

<snip>

>Then why do I get any voltage reading when using the heater, and in free
>air?.
>Bruce

The sensor isn't up to operating temp yet. The sensor needs to be above 600
F for it to operate properly. I don't know how hot the heaters get these
things but it is very unlikely it is anywhere near 600 F. The purpose of the
heater is to help the initial warm up time of the sensor from cold. After
the exhaust is up to temp it is not needed.

<snip>

>So what you are saying is that what Bruce is doing wasting his time ? He
can't
>read  AFR off  the 14.7 value? If you could give me the range AFR numbers
when
>sensor is corrected for temp or are you saying this will not help expand
the
>range? Can you define very narrow range (numbers please)?

>Have a great day
>Steve

No I'm not saying he is wasting his time. If the temp of the exhaust stream
is known it makes it very easy to build a table which allows you to temp
compensate the sensor reading. The problem is even with temp compensation a
"normal" sensor doesn't have a great enough range to be useful for "power"
tuning. Even a "wide band" sensor is limited for power tuning.

Because of the way it work an HEGO sensors range can be "extended" to the
point of reading A/F ratios greater than ( or less than depending on your
view) 13:1 But you still have the same problem. It needs to be temperature
compensated. Also the "outside" current pump control has to be calibrated to
known values for the richer A/F ratios before it can be used as most seem to
want to use it.

Narrow range is from about 15.5:1 to 14.0:1. Have any on the list tried
using a O2 sensor to adjust the idle A/F on a carberated engine? Long before
you get to even a 10% misfire rate in the lean direction the sensor reads
>.2 volt. The same is true in the rich direction.  Back the mixture screw
out 1/4 to 1/2 a turn from lean best idle and the sensor goes abovr .85 v.
But as I pointed out in a earlier post the sensor doesn't read on a linear
basis.

It's not because the sensor isn't linear. It's because combustion and O2
content in the exhaust stream aren't linear. From ~ 9.0:1 to ~ 15:1 the
sensor reads .90 v. or greater. At ~ 8:1 and richer the sensor will drop
again to >.20 v. as rich misfire is induced. On the other hand ar most A/F
ratios of > ~15:1 the sensor will read >.20 v.

<snip>

>>   I had hooked the scope probe across the O2, and cold there was no
output,
>> to be expected, but as it warmed up the output swung toward, .2v.  Just
in
>> atmospheric conditions.  Ok, so then it should go way high in pure O2
right,
>> nope went a little over .3, and stopped there.

>I think you have got it backwards. The sensor should be reading a very low
>voltage as there is no difference in the concentration of O2 on both sides
>of the sensor.

In pure O2 the sensor should read low. The design of the sensor doesn't
allow it to "reverse" the process. In other words , if there is more O2 on
the exhaust side than the air side it won't read higher. If you isolate the
tip and flood the air side with pure O2 then the reading will climb.

Scott

P.S. Please excuse the typos. I get in a hurry and sometimes correct them in
my head when I reread them.