Date: Fri, 02 Apr 2004 16:41:04 -0500
From: echristley@nc.rr.com
Subject: Re: [FlyRotary] Re: Rusty's O2 / EM2 problems.
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Reply-to: echristley@nc.rr.com
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> 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?