"Dave Hyde" wrote in message
...
Ray Toews wrote...
Has anyone ever tried using cowling air under the engine as heated air
for carb heat.

Serveral RV-builders including me have tried something similar.
Van's sells a mini heat muff that doesn't do mucgh but serve as
a mount for scat tube, so in essence we're drawing undercowl
air into the airbox when carb heat is selected. Sam Buchanan
has a picture on his website:

http://home.hiwaay.net/~sbuc/journal/engine4.html

about 1/2 way down the page. I did the same thing on an
RV-4 and I get a barely perceptible RPM rise when I select
carb heat, which tells me it's not helping much.

Your call.

Dave 'hot air specialist' Hyde


You get an RPM increase??? Sumpthin' is way, way wrong with that... ;-)

With the exact same setup, I get a barely perceptible RPM decrease...

KB