What must happen for the fuel cycle to occur properly in an engine?

For the fuel cycle to occur properly in an engine, the fuel needs to be effectively mixed with air and introduced into the cylinder at the precise moment for combustion to take place. This mixture should ideally be in the correct ratio to ensure complete combustion, which is critical for achieving optimal engine performance and efficiency. If the fuel and air are not mixed adequately, it can lead to poor combustion, reduced power output, and increased emissions. Proper timing is also essential; if the fuel-air mixture is not introduced at the right point in the engine's cycle, it can cause misfires or inefficient operation.

The process of mixing fuel with air involves the fuel delivering the right amount of energy necessary to ignite when the spark plug fires, in gasoline engines, or when the pressure is increased, in diesel engines. This is why proper mixing and timing are fundamental to the engine’s fuel cycle.