Before talking about intake manifolds, let's think about how air is getting into the engine. In the engine, we have mentioned the operation of the piston in the cylinder, when the engine is in the intake stroke, the piston down the movement of the cylinder to produce a vacuum (that is, smaller pressure), good pressure with the outside air pressure, so that air Can enter the cylinder. For example, we should have been hit by the needle, but also seen how the nurses inhalation of syrup into the barrel! The virtual barrel is the engine, then when the piston inside the barrel out of the pump, the syrup will be sucked into the barrel, and the engine is so that the air sucked into the cylinder.