Paul M. Anton wrote:
Hello All:
When I purchased my 'Coupe the mixture knob was wired full
rich. I asked the previous owner about it and he said that the AI
required it when he did the annual. The plane has the Stromberg
carburetor. Can someone fill me in on why this was done? If the
mixture control is not to be used, why is it there?
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Paul
As far as I know there is no AD saying that the mixture control on
the
Stromberg carburetor must be wired full rich.
I have a 415 D with a Stromberg and I only use the mixture control
at
altitudes above 5000 ft MSL, as recommended by the book. If the control is
pulled to full lean at cruise the RPMs will drop, the engine will run
rough
and if kept at that setting the engine will seriously overheat. Since it
is
not a lean cutoff design it will not shut the engine down while at idle.
Some say the mixture control has little or no affect, so they don't use it
and some wire it full rich. The control is very effective for reducing
fuel
consumption at altitudes above 5000 ft MSL. However the two mixture plates
should be removed at each annual for inspection and cleaning of the series
of holes to keep it working properly. It should however be pushed in to
full rich when landing.
Some carburetors, other than Stromberg do have mixture controls
that can
be used for shutting down the engine and many of them are wired full rich
to eliminate the possibility of accidentally pulling the mixture control
instead of carburetor heat and shutting the engine down in the air.
Hope this helps.
Jack G. (U42)
N103JF
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