Editing Inlet manifold (section)

==Turbulence==
The [[carburetor]] or the [[Fuel injection|fuel injectors]] spray fuel droplets into the air in the manifold. Due to electrostatic forces and condensation from the boundary layer, some of the fuel will form into pools along the walls of the manifold, and due to surface tension of the fuel, small droplets may combine into larger droplets in the airstream. Both actions are undesirable because they create inconsistencies in the [[air-fuel ratio]]. Turbulence in the intake helps to break up fuel droplets, improving the degree of atomization. Better [[atomizer nozzle|atomization]] allows for a more complete burn of all the fuel and helps reduce [[Engine knocking|engine knock]] by enlarging the flame front. To achieve this turbulence it is a common practice to leave the surfaces of the intake and intake ports in the cylinder head rough and unpolished.

Only a certain degree of turbulence is useful in the intake. Once the fuel is sufficiently atomized, additional turbulence causes unneeded pressure drops and a drop in engine performance.