Ox sender actual function

[Mark Wilcutts]

On Wed, 25 Nov 1998, Orin Eman wrote:

> > >Ah, but where the surprise comes in is that at higher misfire rates, the
> > >sensor indicates rich!
> 
> BTW, this part of the test was with a sensor _downstream of the cat_.
> 2% misfire, the cat would handle just fine I would think and you
> wouldn't see any difference.  Above 2%, well, my feeling is
> that the cat can't cope...  

I should've had my morning coffee before writing that. What you said is
one thing they conclude in this paper. 

> And on top of this, they are running
> closed loop... the known effect is that the ECU will start running
> everything a little richer with the misfire.  The cat is only really
> effective in a narrow range.  Is there any surprise that after
> the cat, we start getting a rich indication when we have a forced
> rich condition to start with?

I'm not sure if that is the way they ran the engine tests. To find that
out one would have to look at Reference 1, which is SAE paper 920298
"Emission Levels and Catalyst Temperatures as a Function of Ignition
Induced Misfire" by Tyree. Anyone care to track down that paper? I can,
but it may take a while. 

The title of this paper is really misleading...920289 deals with a test
vessel only. 920298 describes the engine tests.
 
> We really need the rest of the paper.  Do they explain why the sensor
> indicates lean after the cat under normal conditions?

They conclude it is due to the very low concentration of H, CO, and UHC
remaining. I'll scan in part of the "interpretation of results" section & 
post when its ready...

> Also, so far there is no mention of nitrous oxides.  Does reduction
> of the nitrous oxides in the cat provide significant quantities of
> oxygen?  Chemists?

In 920289 they dont use any NOx in their gas mixtures. 920298 is what we
need to see what they say, if anything, about that.