A naturally aspirated engine, also known as a normally aspirated engine, is an internal combustion engine that relies solely on atmospheric pressure to draw air into the combustion chamber where it mixes with fuel and is ignited to produce power. It does not have forced induction through a turbocharger or supercharger. Most automobile petrol engines, as well as many small engines used for non-automotive purposes, are naturally aspirated. Most modern diesel engines powering highway vehicles are turbocharged to produce a more favorable power-to-weight ratio, a higher torque curve, as well as better fuel efficiency and lower exhaust emissions.
Naturally aspirated engines tend to be of a larger displacement, as they lack the extra power provided by a forced induction system. They compensate for it by either increasing the number of cylinders or increasing their bore, resulting in a larger volume of space contained within the combustion chambers. While turbocharged engines can provide more power than a naturally aspirated engine of the same size, naturally aspirated engines offer other advantages. For example, they generally respond much more quickly to the accelerator, giving them greater response, whereas there can be a lag when suddenly asking for increased speed from turbocharged engines.
Advantages of naturally aspirated engines include simpler designs, which can lead to lower maintenance requirements. Disadvantages include increased power loss at higher elevations due to lower air pressure compared to forced induction engines.
In summary, a naturally aspirated engine is an internal combustion engine that relies solely on atmospheric pressure to draw air into the combustion chamber, without any forced induction systems.
