The quality (volume) of fuel, the rate at which it is injected into the cylinders of an engine, and the timing and duration of the injection event are all controlled by the fuel injection equipment. At the beginning of injection, fuel pressure may be as low as 1800 psi to as high as 30,000 psi, depending upon the design of the equipment. The fuel injection equipment must raise the pressure of the fuel enough to overcome the force of the compressed air charge in the combustion chamber and ensure proper dispersion (distribution) of the fuel being injected into the combustion space. Proper dispersion of the atomized fuel in the air charge is an important factor for complete combustion to take place. Dispersion of the fuel is affected, in part, by the atomization process and the PENETRATION of the fuel, which determines the distance through which the fuel droplets travel after leaving the injector tip or nozzle. If the atomizing process results in fuel droplets that are too small, they will not have sufficient weight to penetrate very far into the air charge. Too little penetration results in the fuel igniting and burning before it is properly dispersed through the air charge in the combustion space. Since penetration and atomization tend to oppose each other, a compromise in the degree of each is necessary in the design of the fuel injection equipment.