No Subject

[ducharme at eiss1.psf.ge.com]

Darrell Norquay wrote:

> How does the mixture affect EGT?  Do lean mixtures produce lower or higher 
> temps than rich ones?  
 
> Can you determine if you are at stoich with this method (with any accuracy)?
> Is there a linear relationship between EGT and AFR or is it a complex 
> function?

> Is this a practical/effective/reliable way to adjust mixture?  Is it only 
> useful at WOT, or does it maintain some validity at all throttle settings?

The function beteen A/F mixture and EGT is non-linear (somewhat parabolic)
with a peak that is NOT coincident with stoich.  As you richen the mixture,
the EGT goes down (which is why air cooled engines, particularly aircraft
engines) are run very rich,  As you lean past the peak, the EGT drops slightly
(along with power)  Obviously, there are other factors in play, and since the
EGT also varies with power level using it as a substitute for a lambda sensor
is a challenge in non-linear systems design. 

Check out _Combustion Engine Processes_ by L. Licty, published by McGraw-Hill.  
It's an older academic text on the subject, but has a plot on this function.

Cliff Ducharme
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