DIY-WB... It's alive...

[Bruce]

Engines don't run at stoich..  The ecm toggles the mixture across it.  In
closed loop the AFR AVERAGES 14.7:1.

I can't image a (conventional) gas engine being able to run at richer then
10:1.  Whereas there are lean burn engines that can run really lean.  The
sensor is designed for a given range, if they wanted I'm sure they could set
one up to run from 14.7 to 40:1, by why go so far into a range that for all
practical purposes doesn't exist.
Bruce



From: "John Dammeyer" <johnd at autoartisans.com>
Subject: RE: DIY-WB... It's alive...
> Good description but if the Stoich is 100% utilization of the O2 in the
> mixture how does the catalyst burn off the HC.  Or is that why the WB
> sensors don't do much better than 10:1 AF ratio whereas they can go
> considerably further in the lean direction?
> John

> Behalf Of rr
> Subject: Re: DIY-WB... It's alive...
> As mentioned the O2 sensor responds first & foremost to O2. When the
> exhaust is stoich, the partial pressure of O2 in the atmosphere will
> cause the O2 sensor to generate ~450mV. In order for the O2 sensor to
> detect a rich condition, there is a platinum coating on the sensor cone.
> Platinum being the catalyst it is will burn off the HC by pulling O2
> through the porus cone. This action generates a voltage > 450mV.
> BobR.


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