I know, lots of discussions on this topic. General experience seems to be small or imperceptible RPM drop when it is applied.
I have my ship apart during the annual inspection doing some improvements to systems and thought I would revisit this as well.
I have a Robbins 6" carb heat muff attached to a Sam James induction/filter housing.
My own experience is that I see a very small reduction in RPM when carb heat is applied during run up.
I have his older style muff that has a 2" opening for incoming air the length of the 6" muff.
The output flange of the muff is a 2" in diameter.
Comparing the relative area of the two openings, the 2" flange has an area of 3.14 square inches. The opening has an area of of just about 11 square inches (assuming some loss for the width of the end plates).
The NEW style muff has an opening of 7/8", giving the new style an area of more like 4.8". Should be better.
In order to more closely match the capacity of the input with the 2" output flange, what would be a 'better' width? I know that there will be losses in efficiency as the air flows around the exhaust pipe and then through the less than aerodynamic flange and the other components........ Perhaps an expert on fluid dynamics wants to chime in? Seems like 5/8" to 3/4" may be better?
Keith
N355RV
RV9-A
I have my ship apart during the annual inspection doing some improvements to systems and thought I would revisit this as well.
I have a Robbins 6" carb heat muff attached to a Sam James induction/filter housing.
My own experience is that I see a very small reduction in RPM when carb heat is applied during run up.
I have his older style muff that has a 2" opening for incoming air the length of the 6" muff.
The output flange of the muff is a 2" in diameter.
Comparing the relative area of the two openings, the 2" flange has an area of 3.14 square inches. The opening has an area of of just about 11 square inches (assuming some loss for the width of the end plates).
The NEW style muff has an opening of 7/8", giving the new style an area of more like 4.8". Should be better.
In order to more closely match the capacity of the input with the 2" output flange, what would be a 'better' width? I know that there will be losses in efficiency as the air flows around the exhaust pipe and then through the less than aerodynamic flange and the other components........ Perhaps an expert on fluid dynamics wants to chime in? Seems like 5/8" to 3/4" may be better?
Keith
N355RV
RV9-A