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<< Lancair Builders' Mail List >>
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Hamid, I too have experienced the phenomenom you describe. At 35, I designed
electronic stuff that the US Patent office deemed worthy of patenting
(though working for a big aerospace company at the time, they were assigned
to the company - I got $500 per). At 67, I have a hard time remembering my
telephone number - well, almost anyway.
However, having retained some thinking ability, it occurs to me that as long
as an engine runs acceptably smoothly, there are probably only two
fundamental differences in running ROP vs LOP.
ROP, by definition, means the combustion process runs out of available
oxygen before all the fuel is burned so the cylinders, and especially the
exhaust valves are somewhat awash in fuel-rich, oxygen depleted exhaust gas
as said gasses blast past them. The potential for oxidation of the valves
from this stuff should be quite low. The excess fuel may aid in cooling
things, especially the valves, which ain't all bad.
LOP, on the other hand, means that the combustion process runs out of fuel
before all the available oxygen is used up so the exhaust valves, are
exposed to the residual oxygen in the exhaust gas. Don't know how much
oxygen is actually left in the mixture as it goes out around the exhaust
valve, but any apreciable amount should cause some oxidation over time where
the valve and seat is the hottest. (the higher the temperature, the more
vigorous the reaction, right?). Is it enough to worry about? Beats me, but
it's something I'd think about when pulling the mixture control way, way
back.
Fortunately, I don't have to think about such things with my little
Lycoming, lean just a little too much and it'll start coughing and
sputtering enough to make one get religion real quick! Of course all that
stops if you try to go LOP - so does the noise up front, too! Although I'm
impressed about how quiet my 235 is when it's making like a 200 MPH glider,
I'd rather have the noise of my engine being run somewhat ROP.
Cheers,
Dan Schaefer
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Please send your photos and drawings to marvkaye@olsusa.com.
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