This was a bit of a panic at the time and we had to overcome that problem, but theres another factor which you may not know about, The evaporation of the fuel drops the temprature by 25 degrees, that raises the pressure ratio of the compressor, or the blower to your advantage.So you get that gain with the carburator system that you do not have with the injection system'
Now what on earth does he mean here?
With a carburetted fuel system, the air from the air intake passes through a carburetor -- a device that sprays a fine mist of fuel into the incoming air, and the resulting fuel/air mixture enters the cylinder through the intake valve. In a fuel-injected engine, the air is ducted into the cylinder through the intake valve, and after the intake valve is closed, an injector nozzle sprays a fine mist of fuel directly into the cylinder. For purposes of fuel delivery, it's kind of like having a carburetor in each cylinder.
Fuel injection allows the amount of fuel in each cylinder to be more accurately controlled, resulting in better fuel economy (the fuel in each cylinder is burned more completely) and (for automobilies) a slight increase in power over a carburetted engine.
However, in aircraft, the amount of air entering the engine is much greater. With an aircraft engine, you control the amount of air entering the engine by controlling the manifold pressure -- the pressure of the air (or air/fuel mixture, for carburetted engines) being fed into the cylinders. And this is where caruburetion gets its advantage.
Take a spray bottle full of water and spray some water into the air in front of you, then walk into the mist. The water is at room temperature, the air in the room is at room temperature, but the misted air feels cooler to you. When you spray a liquid into the air, some of the liquid evaporates, sucking heat out of the air, making it cooler. And cooler air is
denser, meaning that there are more air molecules in a given volume. So when you have a carburetted engine, each cylinder's worth of fuel/air mixture will have more fuel and air in it than a fuel-injected cylinder would at the same manifold pressure.
For example, let's assume that the air coming through the manifold is at a temperature of 80° C after it passes through the compressor of both a fuel-injected and carburetted engine. If the fuel injection drops the temperature of the intake air 25° C, then the intake temperature of the carburetted engine will be 55° C. Boyle's Law shows that the intake air for the carburetted engine will have 8% more air mass than the injected engine -- the equivalent of going from, say, 30" of manifold pressure to 32", without stressing the engine. The carburetted engine develops more power at the same manifold pressure than a fuel-injected engine of the same displacement.
So in order to get the same power out of a fuel-injected engine, it has to be larger and heavier than a carburetted engine. Not a
lot heavier and larger, but with a larger engine, the airframe has to be larger and sturdier, which gives a plane with a carburetted engine an edge.
