More on EFI Re: <VV> Fiero FI

[FrankCB@aol.com]

In a message dated 5/17/04 12:05:07 PM Eastern Daylight Time, NicolCS@aol.com 
writes:
The popular aftermarket ecm 
these days is the "Megasquirt" unit, which has the advantage of easy 
reprogramming vs. the Fiero style factoyr programmed ecm.  The Factory 
programmed ecm 
has the advantage of self-correction through feedback from the O2 sensor.
Craig and John,
    The disadvantage of the Fiero (and most other) factory programmed ecm 
self-correction (called feedback) is that it will only ensure that the A/F ratio 
goes to stoichiometric (around 14.7) since the O2 sensor used is a NARROW band 
one.  If you want to control the A/F at anything else other than 
stoichiometric you have to hope that the original factory calibration of 
NON-stoichiometric operation in the Fiero (like full throttle) will create what you want in 
your Corvair.  The Megasquirt unit (as well as other non-factory units) can be 
interfaced with a WIDE band O2 sensor that allows you to actually program in any 
reasonable A/F ratio you want at various rpm and load conditions.  So you can 
have A/F = 16 for light throttle cruising economy and also have A/F = 12 for 
full load, high rpm, high boost conditions.  Even if you do install a wide 
band O2 sensor into the Fiero system (by replacing the stock O2 sensor), I don't 
know of any way you can "get into" the software programming of the factory ecm 
to take advantage of it.  This software is generally considered proprietary 
by the auto mfrs. and is extremely complex even if you could get a bootleg copy.
    Frank Burkhard