Dean Zywicki wrote:
> My midget started idling real rough a few weeks ago. After a
> conversation with my dad and that his cars (all carburetted) were doing
> the same thing I started thinking. He blamed it on the oxygenated gas
> that started November 1st. I had been checking the plugs on my midget
> and I noticed that they were real white (indicating a lean mixture).
Lee Daniels replies:
> No, the "oxygen" in this case is just in the form of additives, i.e.
> liquid compounds which contain oxygen atoms; in this case they are ethers.
> [...]
> I believe that the standard "oxygenated" additive is methyl-tert-butyl-
> ether, i.e. MTBE, [...]
MTBE has been used, but (on the left coast) has been almost totally
replaced with a 10% ethanol blend. (I've heard that it's cheaper for the
oil companies because of gummint subsidies or tax breaks or something.)
Ethanol (C2H5OH) has the same effect as methylated ethers, that is to
provide an "extra" oxygen atom to the combustion process. This "extra"
oxygen atom has the effect of promoting the production of CO2, especially
when the engine is cold, which, in turn, reduces the production of carbon
monoxide (CO) (not NOx, as Lee mentioned).
Anyway, back to Dean's problem:
> With a carburetter, which basically runs on volume of gas, it isn't
> getting the right amount of combustibles per volume, thus a lean mixture.
You may be right, but not for the reasons you think. There isn't enough of
a concentration of additive to change the stoichiometry of the air-fuel
mix much. What has happened out here is that the first tank of the ethanol
blend absorbs all of the water that's collected in the tank over the
year(s), which usually includes all of the rust and crud that's also on
the bottom of the tank, which eventually makes it into the fuel system. So,
if there is enough water, you get crappy running until it's all been pulled
through the engine. And you can also get clogged fuel filters and
carburettors as a bonus! Which could be the cause of your lean running.
Don't adjust your carbs yet Dean! Burn up that first tank of "oxygenated"
gas, if you already haven't. Then, replace your filter(s), clean out the
sediment bowl and screen in your fuel pump (if your Spitfidget is so
equipped), and maybe even clean out your carburettor bowls. THEN, readjust
your carbs, if your engine still runs rough.
I've heard many people disparage oxygenated gas for the wrong reasons, and
my cars actually run a little better with it because of the slight increase
in effective octane the ethanol provides. But I do also get lower fuel
mileage, some because of the colder weather, some just because of the
lower energy content per unit volume that ethanol has than gasoline.
Pat Vilbrandt Fluke Corporation Everett, Washington USA
pwv@tc.fluke.COM or: { uunet, uw-beaver, sun, microsoft }!fluke!pwv
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