It might sound counterintuitive but all induction is forced. Yes, even naturally aspirated engines. Gale Banks explains that as the piston in the engine drops during the intake stroke, a near-perfect vacuum is created above the crown of the piston. The difference in pressure from that near vacuum to the air pressure in the intake manifold is what forces air into the cylinder. In a naturally aspirated engine that manifold pressure is simply the ambient air pressure (with a small margin depending

Heavy breathing! There is a whole new level of expertise needed to build a naturally aspirated engine. Unlike turbocharging, u have to find ways to make the engine create more bang by allowing more air to enter by no means of forcing air into the cylinders. The engine creates a vacuum effect that draws air naturally and thats where the efficiency game starts. While manufacturers like Honda chose the difficult path of making great NA engines, most chose to simply turbocharge and not be too bother