O2 sensors at WOT?

[Roger Heflin]

On Mon, 2 Nov 1998, Bill the arcstarter wrote:

> List,
>  I've heard that most ECU's go into an open-loop condition while under 
> WOT.  I've also heard this is because most O2 sensors read incorrectly 
> under WOT conditions.
> 
Yes.  Generally actually below wot, there are settings in the prom to
control what tps at what rpm will go open loop.

> Why is that?  Does the increased gas flow cool the O2 sensor down too 
> much or what?
> 
The O2 sensors are nonlinear, that is small changed in the output
value can be actual big changs in the real system.

> Is the decision by the ECU to go open loop - based on TPS alone or on 
> (what) else??
> 
Everything I am familiar with asys only TPS but differeent rpms take
fdifferent TPS to go open loop.


> Someone else said that a heated O2 sensor will respond to hydrocarbon 
> levels if it is not warmed up properly.  If this is true perhaps a poor 
> man's gas analyzer could be constructed using one heated (to measure O2) 
> and one unheated to measure hydrocarbons, etc???
> 

No.  What the report said (I read it) was that NO O2 sensor senses O2
at the temperatures that they operate at.  They sense hydrocarbons
only.  The temperature required for them to sense O2 was much higher
than the O2 sensor in a normal exhaust stream was supposed to be
getting (heated, or unheated).   So the claim was that O2 sensors
sense hydrocarbons, which should really work much the same as if it
senseed O2.  That also might be why (at least at the rich end) that
things go nonlinear, since it would be hard to detect more of what
you already have alot of. 

 >
Thanks! > -Bill > 
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