I did not imply that the mix in the combustion chamber was pure liquid, but it is a pretty darn rich vapor consisting of both gasoline and oil molecules. Thanks to turbulence and heat in the crankcase, the fuel/oil mix gets "turbulated" or mixed with air in the crankcase.
"You also dodged the question about the different boiling point components(gas,oil) reacting to intense heat-IE crankcase."
In the most basic 2-cycle engine, an inclined reed valve (or equivalent) allows the liquid mixture to be sucked into the lower crankcase chamber on the upper portion of compression upstroke, since at this time there is a lower pressure in the crankcase. Some of the liquid fuel/oil is mixed with air and so forms a fuel/oil "mist" in the crankcase. Also at this time, this mist lubricates the needle bearings, the piston wrist pin, and the crankshaft end bearings. Because the viscosity of the mix is so low (0.25 to 0.75 cSt), only special ball bearings or needle bearings are used. Due to the turbulence associated with the motion of the crank/piston, and due to convected heat, the energy of the mist is raised. But again, this mixture contains both both gas and oil and is stoiciometrically very rich. After combustion, the piston moves down to expose the exhaust port where a "portion" of the burnt gases are expelled. AT the same time, with the downward motion of the piston, the volume in the crankcase is reduced (compression of mist below the piston in the crankcase) and the fuel/oil mist is further heated. As the piston decends further down in the crankcase, the intake port is exposed and the previously compressed mixture flows into the combustion chamber. Heat of combustion from the previous combustion cycle and heat of compression in the crankcase raises the energy levels of the rich fuel/oil mist, which allows better burning of this rich mist/vapor.
You have to also realize that when the mix is sucked into the crankcase, the fuel/oil mix lowers the crankcase temperature somewhat due to some evaporative cooling. In addition, the crankcase temperature never reaches the temp of the upper combustion chamber, i.e., the head. If it did, fuel vapors would buld up and it would explode. If this were the case, the only hydrocarbons getting to the combustion chamber would be the oil hydrocarbons, which would result in intense smoking, signifying incomplete combustion.
BTW, I am still waiting for a 2-cycle diesel chainsaw which has a little roots blower (for better scavenging), fuel and compressed air injection (for better combustion), and electronic valve timing.
[ October 09, 2003, 11:49 AM: Message edited by: MolaKule ]