Blake wrote:
<<<snip>>>
"Somewhere I thought I once read that an internal combustion engine gets its
best fuel economy at something like 90% of full throttle. Now that doesn't mean
90% of its maximum engine speed, but 90% of FULL THROTTLE. That would indicate
that if you can maintain that throttle position when going up hill, against the
wind
etc., and maintain the steady speed you want with the OD, then it will most
likely get the better fuel mileage even with more throttle than with the OD
disengaged and less throttle."
<<<snip>>>
Well, has anybody done any real research? Are you just going by what you
thought? Was the phrase "internal combustion engine gets its best fuel economy
at something like 90% of full throttle" way off? Should I have used the "car
gets its best fuel economy at 90% of full throttle" or was it correct in using
"engine gets its best fuel economy...?" What about the 90 per cent? What
about...?
Consider the situation again.
You have your MGB in OD and because of the wind and load conditions, (hills,
horse trailer, etc.) you have the throttle ALMOST wide open to get 60 mph out of
the car. The manifold vacuum is low?
You disengage the OD without changing the throttle position. (Poor way to do it
but necessary for the explanation.) The engine RPM's go up and the engine is
now developing more horsepower (throttle is still almost wide open) which is
more than what is needed. The MGB starts increasing in speed so you throttle
back to maintain the 60 mph. With less throttle the manifold vacuum goes up?
Under which condition is the engine getting the best fuel economy?
Blake
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