In my small knowledge based opinion, combustion engine works by combusting fuel while using an oxidizer as a process enhancer.. in road cars' case that oxidizer is air.. when the air is inducted in the process, it is routed to combustion chambers..
Now why do we use forced induction kits to enhance power? because we have just routed the air in stock cars, and there is nothing forcing it in.. Now forced induction kit is a step further..
However, this fan thingy is a smaller step towards more performance advantage.. how? the air moves through filters, through pipes and then engine... as it is scientifically proven that air moves with more force when its moving in spirals (torpedos etc).. giving a spiral motion to the inducted air, we are actually facilitating its movement all the way towards the pistons.. this is all..
Now to gain appropriate amount of advantage from it, what is required is optimum fuel and air mixture, and optimum balanced inlet and outlet mouths and pipe sizes for air flow.. if you give it more air, that too moving in spirals causing less resistance by side walls, you're gonna need just as much of fuel and piston action to process it, and appropriate size of outlet..
It barely adds 1-2% to the HP, but it makes it easier for the engine to process air.. Its a small thing that adds small value, kinda like installing a tiny dedicated oil breather..
