This vacuum can also be passed down to draw any piston blow-by gases from the engine's crankcase. This is accepted as a closed crankcase ventilation or positive crankcase ventilation (PCV) system. This habit the gases are burned with the fuel/air mixture.

The plenum of a 6 or 8 cylinder engine can be parted into halves, with the even firing cylinders in one partly and go the freaky firing cylinders in the other part. Both sub-plenums and the wind intake are connected to an Y (sort of main plenum). The stratosphere oscillates between both sub-plenums, with a large pressure oscillation there, but a monophonic pressure at the main plenum. Each runner from a sub plenum to the main plenum can be changed in length. For V engines this can be implemented by parting a particular large plenum at altitudinous engine speed by means of sliding valves into it when speed is reduced.