i have a question... regarding the cd-150's, and changes in altitude.
will there be a need to re-tune with any great change in the altitude i
am driving at. i can, in less than an hour, be driving at 6000 ft, up
from 1300, and i want to be aware if there is a potential problem.
while working on an airplane sat. i noticed that the rotax powerplant
(not a motor or engine!!) used constant depression carbs, and were
"altitude compensating". i'm wondering if this is inherent to CD type
carbs, or is it just a feature of the carbs on the rotax. i cant tell if
it is a designed feature of the rotax carbs, because i really don't think
the owner would like me to pull them apart to find out, and schematics of
the mechanism were not readily available.
i am of the opinion that since the airvalves work relative to air
pressure, and the ratio of vacuum to outside airpressure will stay the
same, that they will not have to go through a mixture adjustment. with
less outside pressure, the manifold vacuum will not "pull" the valve as
high at altitude, due to the outside pressure not "pushing" the valve as
hard as it would down low, with the net result of a "leaner" relative
mixture that is correct for the lower air density at altitude.
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