This is what I've pieced together from many different sources, including this web site. Some of it is theory, and some fact. Any, if not all, can be disputed.
Here are several reasons for the major inefficiency of the gasoline engine.
Gasoline, as a liquid, does not ignite. A carburetor, or fuel injection system, atomizes fuel, which is not the same as vaporizing. The carb, or FI, turns the liquid gasoline into tiny droplets ( still a liquid). Thats not to say that none of the gasoline vaporizes. Gasoline is made up of hydrocarbons (Hcs) of varying composition. Some will vaporize at very low temperatures ( I don't know how low, 30 – 40 degrees?). Some as high as 450 degrees. So when the air/fuel mixture is drawn into the cylinder, some is already in the form of a vapor. The compression stroke creates heat which causes more fuel to vaporize. As a percentage, I think the amount of vaporized fuel is still low. When the spark plug fires, it ignites the portion of the mixture that is already vaporized. As the vaporized portion begins to burn, it creates more heat which ignites the slightly heavier hydrocarbons, which creates even more heat, which ignites the slightly heavier HCs, and on and on, until it has all burned, or the exhaust valve opens. Much of the energy available in the fuel is wasted because it burns too late in the combustion cycle. It creates a lot of unnecessary heat. And, the late burning fuel, also known as end-gas, is what makes detonation possible.
Another reason for inefficiency is that in order to complete combustion on time, the ignition timing must be set to occur before top dead center, the amount varying with engine design variations. Combustion beginning before top dead center causes mechanical inefficiency. The piston is still rising in the compression stroke at the point combustion begins, meaning it must fight the rising pressure before it can even reach the power stroke, which is a drain on power.
If the fuel is fully vaporized before it enters the combustion chamber it burns very rapidly. This means the timing does not need to be advanced nearly as much, increasing efficiency, and power. Because it burns rapidly, and completely, it greatly reduces or eliminates the risk of detonation.
This drastic increase in burn efficiency means that the amount of fuel, and air, necessary to produce a given amount of power is greatly reduced. I've also read than when running fully vaporized, you can run a mixture as lean as 20:1.
Thats some of what I've learned. Now for some of my questions, and concerns
How would you measure a mixture as lean as 20:1?
Is there a point where the mixture will become too lean to ignite?
Timing... I'm thinking initial timing might be at zero or just a few degrees before. Total advance? Zero? or very little?
How to determine optimum timing? I'm thinking to modify a distributor by locking out the mechanical advance and using only the vacuum advance. Then make a device to vary the vacuum going to the distributor while driving to permit on-the fly experimentation.
Here's what I'm working on....
Engine build -
390 flat top pistons
zero deck height
stock cam
stock head
FI exhaust manifolds
4 bl intake
1bbl Constant velocity carburetor
Heat exchanger (vaporizer)
DS II distributor
GM module
super coil
water (steam) injection
I'm beginning to wonder if the 390 pistons/zero deck height is necessary
