Message-ID: <003901c41930$ce49bc80$2402a8c0@EDWARD>
From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-3142981@logan.com>
Subject: Lead fouled O2 sensors
Date: Fri, 2 Apr 2004 23:04:47 -0500
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

Ernest,

    I was probably not clear about lead fouling. Leaded gasoline WILL
contaminate the O2 sensor reducing its sensitivity and the reaction time of
the sensor.  This renders the O2 sensor essentially useless for the auto
computer to maintain the emission control desirable air/fuel ratio of 14.7:1
because the reaction time of the sensor slows down due to the contamination
and the computer is receiving out of date information (so to speak).

The sensor can still detect relative O2 levels even when contaminated -
however, it does not react as fast to changes. Lead will eventually
compromise the function of the O2 sensor, but  I have flow 100 hours with
nothing but 100LL avgas before I replace my first O2 sensor.  It was still
indicating but the voltage range was compressing so that the range of
indicators were only 5 LED lights rather than the normal 10 range.  So while
a few seconds of lead gas may kill an O2 sensor as far as automobile use, I
can tell you that from experience with my first (100 hours) and my second 20
hours of 100LL use, it does not render them useless for our purposes - well,
at least until a considerable number of hours.  The auto computer is
expecting reaction time on the order of a few milliseconds while the
human/eyeball/brain requires on the order of 100s of milliseconds
to sense/process same.

Now all these applies to the older style of O2 sensor.  I have no experience
on the newer more expensive broadband O2 sensors.

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message ----- 
From: <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Friday, April 02, 2004 4:41 PM
Subject: [FlyRotary] Re: Rusty's O2 / EM2 problems.


>
> > MessageRusty,  the O2 sensor in itself does not
> cycle, but only in
> > response to changes in the oxygen content of the
> exhaust.  The
> > reason that "cycling" is seen in automotive
> applications is the EFI
> > CPU of the auto is "hunting" for the optimum ratio
> for emissions
> > approx 14.7 air/fuel ratio.  So if it senses too
> high an oxygen
> > contents (varies from 0.45 volts or thereabouts to
> 0.0 volts) it
> > increases the fuel content which likely overshoots
> the desired
> > ratio so then the computer senses this overshoot
> through the o2
> > sensor and so quickly corrects the mixture by
> decreasing the fuel
> > content.  This seesawing between over and under
> the desired voltage
> > (approx 0.45) causes the O2 sensor to send out a
> "Sawtooth" wave
> > form of voltage varying from under 0.45 volts to
> over 0.45 volts
> > and under certain conditions and probably approach
> 0.0 to 1.0 volts
> > in swing.
>
> Sounds like a problem that would be solved perfectly
> by the application of a little fuzzy logic, or are
> the sensors so sensitive that ANY O2 will turn them
> full on?  The other side of the equation could be
> that once you're somewhere around the sensor's
> switching point, it's not worth the work to optimize
> any further.
>
> > In the automobile use Lead will quickly decrease
> the sensitivity of
> > the O2 sensor to the point that it is relative
> useless for the
> > emission control purpose since it is trying to
> maintain an optimum
> > by quickly sensing and responding to an over or
> under oxygen
> > voltage signal.  In our application we more or
> less use it as a
> > trend indicator Rich, Lean, Going Rich, Going
> Lean.  Millisecond
> > response time is not required for our reaction
> time {:>).
> >
>
>
> Ed, that last statement has me confused.  I've read
> several posters who have had to replace O2 sensors
> due to lead fouling.  Is it something else killing
> the sensors?
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>