Hiway747 works!(A little EFI content)

[Dave Williams]

-> <EFI content> Gas mileage with hiway mode at 18 AFR was less than at
-> 14.7. I guess the lean mixture put the engine into a higher MAP
-> region thereby using more gas. There must be a point of no return
-> between 14.7 and 18.

 According to the literature the decrease in mileage with high AFRs is
due to lean misfire, which requires a higher throttle setting and
eventually more fuel to replace what isn't burned.  You should be able
to tell if you're getting misfire by watching the O2 sensor for rich
spikes.

 Most Detroit V8 data I've seen indicates the sweet spot for mileage is
closer to 16:1.  As far as I know it's due to stock-type ignitions.
Lean cruise is the place where you *need* a God-Of-Lightning killer
ignition system to stretch the lean misfire point out a bit more.  Even
a flicker will do the job at stoich; lean is much harder.

 If you're not maxed out on spark advance you might try working on that
since it's just a chip tweak, but with non-EFI cars I've managed to get
into the region where the rotor in the distributor was so far advanced
the spark just jumped to the closest cap terminal instead of the plug
gap.

==dave.williams at chaos.lrk.ar.us======================================
I've got a secret / I've been hiding / under my skin / | Who are you?
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