Ethanol does indeed have a higher octane (resistance
to self-ignition) than gasoline but it also provides
substantially less energy per gallon so you need to
burn more of it to get equivalent power from the same
engine. Modern "flex-fuel" EFI engines are able to
automatically adjust the fuel/air ratio depending upon
what's in the tank at any given moment, but a
carburetor can't perform that trick - you'd need to
increase the fuel jet sizes by 30% or so over what's
needed for straight gasoline to keep from running
dangerously lean. Problem here is that "E85"
encompasses all mixtures from nearly 100% gasoline to
15% gasoline, so without a reliable consistent supply
it'd be impossible to run fixed jetting.
Another issue is that alcohol can be corrosive to some
types of rubber used in the fuel system (the
accelerator pump diaphragm, for example).
It is possible to recoup the power lost from the lower
BTU/gal by raising the compression ratio (the high
octane makes that feasible) but an engine assembled
that way will never be able to safely run straight
pump gasoline again.
If you live in a region where E85 is readily available
and can be counted on to always be right around 85%
alcohol, you could jet your carburetor to run on it
but your MPG will be significantly lower unless you
also build the engine with a much higher compression
ratio.
Figuring upon about 30% worse mileage, $2.79 compares
to around $3.63 for gasoline. It might still be less
expensive per mile, but you will need to rejet and
even then the power output will be commensurately
lower - it'd take a much larger cost/mile differential
before I'd be enticed to fool with it, personally.
--- Timothy Osburn <[EMAIL PROTECTED]> wrote:
> I was on vacation in my Bus last week and ran into
> some gas stations that had E85 ethanol for
> $2.79/gal. It was rated at 100 octane! I am
> surmising this fuel would not be a go in our old
> air-cooled engines. Would I be correct and can
> anyone tell me what it might do to the engine if you
> ran it?
> Tim Osburn, Head Mechanic, Ralph Spoilsport Motors.
>
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