AFR control

[Eric Elliott]

Hello,
Having read so much mail about wanting a linear exhaust gas sensor, I 
considered how to do with what we have. Could be an original thought or 
maybe this is in a book I haven’t read yet, but here goes....

Maybe the HEGO could be used at stoich to get the correct non-stoich 
AFR.
 
Given:
We need accurate air/fuel ratio (AFR) control over a wide range of 
AFR’s. 
The HEGO is accurate only at stoich.
Accurate direct linear AFR measurement is expensive and shortlived.
Volumetric efficiency  varies wildly with RPM, throttle opening, 
weather, temperature, etc.
Engines can’t sustain operation at high load and stoich AFR.

Maybe:
Starting with conservative (rich) fuel fuel table values, the 332 could 
determine in a few power cycles the injection duration needed to get 
stoich (get a useable stoich output from the HEGO), then return to the 
conservative (rich) fuel fuel table value. Desired AFR could then be 
calculated from the stoich value, and the original fuel table value 
altered.
Restated, the engine could, at a given RPM & load, be switched to 
operation at near stoich for a few cycles, then returned to safe rich 
operation. After a few trials, stoich operation could be measured via 
the HEGO, then accurate calculation of the desired fueling could be 
done. 
In economy cruise this could be easy and risk free. At max effort, to 
avoid engine damage, the 332 would have to severely limit consecutive 
cycles near stoich.
If the stoich determination is done on a cylinder by cylinder basis, 
the momentary (V8) power deviation would be much less than a 6% power 
loss at worst. At the same time, individual cylinder & injector 
matching data could be collected. Arbitrary open loop fuel table values 
could be replaced by ideal values without extensive dynamometer time. 
The 332 could always be refining the fuel table values.

Is this a workable AFR control procedure?

Eric