Whoopee

[Kenneth Blackwell]

As I feel sure that Lance knows, the water condensation on the outside of the carb body is caused by the carburetor venturi. When you pass air through a venturi it gets cooler causing the carb body temperature to drop, like a little refrigerator. Then, if the outside of the carb body is below the outside air dewpoint condensation will form on the outside of the carb body.

Full scale light airplanes with carburetors have a heater to warm up the air going into the carb on those cool wet days....to prevent internal carb icing.

We here in the south often see days when the air is thick with moisture. So, we also see moisture on the outside of the carb when running it on the ground.  Out west where the air is extremely dry, you won't see this moisture on the outside of the carb.

Now, I don't know what this has to do with idle speed, but it could be that the extra moisture in the air going into the carb is part of the problem. Ram air going into the carb in flight has a slightly higher temp than that on the ground without RAM effect...but this difference is probably very very small.

Just thinking out loud.

Cheers,

Ken Blackwell

----- Original Message ----- 
From: Lance Van Nostrand 
To: discussion at nsrca.org
Sent: 6/17/2004 11:06:31 PM 
Subject: Re: Whoopee


I'm not so sure the housing is warmed much.  I run a lot of engines on the test stand and often see condensation on the housing.
--Lance

----- Original Message ----- 
From: Nat Penton 
To: discussion at nsrca.org 
Sent: Thursday, June 17, 2004 12:28 PM
Subject: Whoopee


The question was  brought up by Mike East recently about why the two stroke lands at a higher idle setting than it takes off. And the answer is - the carb barrell is cooled by the pressure drop and the housing is warmed by heat transfer. The barrell is insulated by the oil film and cannot shut off the flow of air.  Solution anyone? Plastic case?              NatPenton
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