I'm not sure if that is definately true Woody, but I know they work with fluid! Lol! Had to learn all about it for my gas engineering qualification. Water heaters and some old combi boilers use a venturi. When the water is released from a tap, the water flowing over the venturi creates a back presure and the differential presure pushes a rubber diaphragm up, which acts on the gas valve, allowing the boiler to fire.
So in theory, the air flowin over the venturi would create a back pressure, which helps with torque. That's if I'm right?
Lol!