The Murphy Builders Site

Alan,
When you went to the cabin heat muff replacing the open sided standard carb heat muff did you also add a positive pressure feed to the cabin heat muff? Are you using the standard Van's "standoff" at the airbox or did you create a heat dump valve?
Ralph Baker



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Ralph:

No on the positive pressure feed, and no on the standard standoff. I
replaced the standoff with a 2" flange, so there is no substantial leakage
path for cold air. Frankly, it seemed that with the standoff, the cold air
path would be the path of least resistance, so 80% of the induction air
would be cold. Now, I admit to some concern that the engine might just not
get enough air through a 2" scat hose, but you typically don't use carb heat
with the throttle wide open (or if you do, the throttle is already
restruicted by ice), so I think that angle is probably OK. If the engine
was really starving for air, it'd suck the carb air door open anyway. I do
not see a big cahnge in the carb venturi temperature as meastured by my
Grand Rapids probe, but I suspect that is measuring carb body temperature.
Not quite sure hoe I could confirm that,

P.S. How goes the project? Temperatures must be returning to comfortable
building conditions. I may be back at Sun'n'Fun next spring, so be ready
for a snap inspection!

Al.





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I will post a pic on the website if there isn't lready one there, but it
will show the standard open sided muff.

Al





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