Message text written by Randall Young
>> Clark, I think if you run the numbers it is not as bad as you
> think. While
> it is true that alcohol has less heat energy per gallon than gasoline, it
> is not completely devoid of heat energy. It may be as much as 25 - 30 %
> lower but at only 10% content this reduces the heat energy per gallon by
> 2.5 to 3%.
Problem is, it (deliberately) screws up the mixture. On cars that were
already tuned lean (eg anything sold in the US after about 1968), they can
be pushed "over the edge" and become so lean they don't run right. The
result is a more dramatic loss in power, fuel mileage ... and a big
increase
in emissions !
I've never bothered to check it myself, but a friend with a TR4 recently
told me he got 10-12% better gas mileage on a trip to Vegas, after filling
up with non-oxygenated fuel. However it's not a strictly accurate
comparison, since California's "Phase 2 RFG" is not the same as the federal
RFG.
<
Fortunately for us, we can adjust the mixture to compensate. It has been
my experience that the cars with catalytic converters are set intentionally
rich anyway (I guess to ensure that the converters have something to work
with over the variations of mixture you get with carburettors) and a little
leaning out doesn't hurt.
Here in the heartland we get gas with 10% methanol and I have not noticed
any change in either performance or economy. As a matter of fact, on my
way home from VTR last year, I stopped to fill up in Iowa and instinctively
went to the regular pump (the TR8, at 8.13:1 CR runs fine with regular) and
was almost full when I noticed that the price for regular was one or two
cents higher than midgrade! That was when I noticed that the regular
contained no alcohol whereas the midgrade contained 10% alcohol (like all
the other gas I bought on that trip). I did not notice any difference in
either performance or milage with that tank of gas as with the other 5 or 6
tanks I bought on that trip.
So, I suppose that if you are borderline, 10% methanol can push you over
the edge but, at least with SU's and Strombergs, we can adjust to
compensate.
Or perhaps midwest corn makes better alcohol than the stuff you grow. ;-)
Dave
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