Post by norfolknchance on Jan 28, 2013 19:41:05 GMT 1
CARB VENTING
As we have now seen, the CV carb needs the presence of outside air (at atmospheric pressure) inside the carb for several reasons:
--Outside air is needed under the diaphragm to push it up.
--Outside air is needed above the fuel in the float bowl to push down on the fuel and force it up past the various jets and into the starting, pilot and run circuits.
--And outside air is needed to service one or more of the air jets that reside inside the carb body..
How does this outside air get in? It gets in through the breather pipe which sits toward the top of the carb just under the diaphragm. Air jet(s) also reside in this space and have access to it. And drillings in the carb body allow the outside air to go down and enter the space above the fuel in the float bowl.
A breather tube typically attaches to the breather pipe and extends to some point (e.g., behind a side cover, or inside the aircleaner pod) where the air is relatively calm. Why? We don't want wind to be changing the airpressure at the end of this pipe, because this will disturb the operation of the air jets, the diaphragm, and the fuel delivery. These functions need consistant outside air pressure to work properly against the various levels of depression created in the bore, above the diaphragm, etc., as the carb goes about its work.
As we have now seen, the CV carb needs the presence of outside air (at atmospheric pressure) inside the carb for several reasons:
--Outside air is needed under the diaphragm to push it up.
--Outside air is needed above the fuel in the float bowl to push down on the fuel and force it up past the various jets and into the starting, pilot and run circuits.
--And outside air is needed to service one or more of the air jets that reside inside the carb body..
How does this outside air get in? It gets in through the breather pipe which sits toward the top of the carb just under the diaphragm. Air jet(s) also reside in this space and have access to it. And drillings in the carb body allow the outside air to go down and enter the space above the fuel in the float bowl.
A breather tube typically attaches to the breather pipe and extends to some point (e.g., behind a side cover, or inside the aircleaner pod) where the air is relatively calm. Why? We don't want wind to be changing the airpressure at the end of this pipe, because this will disturb the operation of the air jets, the diaphragm, and the fuel delivery. These functions need consistant outside air pressure to work properly against the various levels of depression created in the bore, above the diaphragm, etc., as the carb goes about its work.
