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I believe that most of us understood that leaded gasoline
can lead to spark plug fouling. It turns out even with the
"Scavenger" compounds it apparently will still happened. See article
below:
I also read one report that address aircraft engine
effect. It basically said that if the CHT is not kept over 350F the
scavenger effectiveness is minimal. So this may be why aircraft sparkplugs
do not seem to foul as often as the auto plugs (higher CHT).
URL
:http://www.petroleumbazaar.com/MS/msappli2.htm
During combustion TEL (Tetraethyl
lead ) forms an oxide of lead which is not volatile and so should tend
to deposit on the combustion chamber, valves, spark plugs, etc. with harmful
effects. To counteract this. "Scavenger" compounds, such as ethylene dibromide
and ethylene dichloride, are mixed with TEL so that on combustion more volatile
compounds of lead are formed, resulting in most of the metal passing out with
exhaust gas. The TEL together with the scavengers
and a dye to indicate the poisonous nature of the compound is known as "ethyl
fluid".
Despite the use of decavenger compounds, it can
give rise to such difficulties as: sparkplug fouling, surface ignition, exhaust
valve failure and octane requirement increase.
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