experimenting with a carb..

[drcoopster]

I purposely wrote "atomize" instead of "evaporate". If someone knows better, please correct me, but I believe that gasoline going out the venturi mostly atomizes in air instead of evaoporates. That is, it becomes suspended in fine droplets. An atomized material can eventually evaporate, which means that individual molecules exist in the gaseous phase. Evaporation is ideal, and fine atomization is very good. One reason that this matters is that liquid droplets are much denser than gaseous molecules. Every time the flow of the air-fuel mixture changes speed or direction, small droplets slam into each other, or the side of the tube, and coallesce into bigger droplets, which don't burn as well.

I believe you're mostly correct about that. Gas is supposed to atomize out of the carb jet but before it reaches the point where it's to ignite, it should be in vapor form. Atomized fuel vaporizes easily, assisted by the low static pressure inside the carb venturi.

Don't air-cooled piston airplane engines have a different source of carb hear?

Yes, air-cooled reciprocating aircraft engines basically run an air-to-air heat exchanger to heat fresh air using heat from the exhaust. This air is then piped into the carb to help remove any ice that has formed inside the carb and/or to prevent ice from forming. This is manually-controlled, though. Fuel-injected reciprocating aircraft engines do not need carb heat because there is no venturi where ice will form.

[ihalterman]

Cold air is more dense( higher concentration of oxygen).
Hot fuel will vaporise more with less effort.

A cold air intake allows you to add more fuel to the mix. (more oxygen + more fuel = more power)

Hot fuel would vaporise more evenly and with less work. Not all of the fuel going into an angine get vaporised so not all of it burns. (Same oxygen + same amount of fuel Vaporised more = More power)

That's my $0.02

BJ