....I have some bad news for majortom and DarZeelon....your ideas, theories, concepts,
understanding....or whatever you want to call it, about the operation of these simple
aero-engine carburators is incorrect. I don't know any other way to say it.
Both of you are in disagreement with the explanation offered by Webra Engines, are you not ?
Both of you agree that the low speed, or idle adjustment is the primary fuel adjustment, that
controls the carb operation. You say the high speed adjustment is just the secondary adjustment....yes ?
DarZeelon:
"Even at 3/4 open throttle, the mixture strength in nearly all two-needle carburettors, is still
dependent on the setting of the low-speed needle only.
Since the high-speed needle only controls the mixture strength in a very narrow throttle range,
it is the less important fuel control, hence; 'the secondary fuel control'.
The low-speed needle, responsible for the mixture setting over 75% of the throttle's range, IS the
more important, hence 'the primary fuel control"
majortom:
"with a two-needle carb, the low needle is the more crucial part of the design, since it sets the
foundation on top of which the high needle performs its more limited function. On the two-cycle
glow engines with which I am most familiar, it is the low needle which moves in and out to open
or restrict the fuel flow, and it moves whenever and wherever the throttle arm moves, whereas
the high needle stays put no matter what the throttle arm does. That makes the low needle the
primary fuel control mechanism. This understanding clarifies a lot of rules"
The explanation offered by Webra Engines differs with your explanation. Would either of you
like to change your story ?
FBD.
