What is a naturally aspirated engine?
If you’ve been following automotive content for any amount of time you have likely heard or seen that people tend to have a preference for naturally aspirated engines. Now you may be asking, what is a naturally aspirated engine? A naturally aspirated engine is an engine that does not use forced induction, meaning that it does not use turbochargers, superchargers or any other means of forcing extra air into the engine – it is simply an engine.
What is forced induction?
Now that you know what a naturally aspirated engine is, lets quickly talk about forced induction. Turbochargers can allow smaller engines to produce the same amount of power as large engines, while consuming less fuel. So, a turbocharged engine could offer both more power and better efficiency than a naturally aspirated engine. Of course, a turbocharged engine will suffer from boost lag. Boost lag refers to the time it takes for a turbocharger to spool up and deliver power. Turbochargers are spun by the exhaust gases, so first the engine must produce exhaust gases before the turbo can produce power, hence causing a turbo lag. Superchargers on the other hand do not suffer from any type of lag, they are belt driven and deliver power almost immediately when the throttle is hit. Supercharged engines can produce much more power than naturally aspirated engines with nearly no lag. Superchargers do greatly decrease efficiency, since they are not fed by exhaust gases, they are simply requiring more fuel to operate.
What’s so great about naturally aspirated engines?
After reading the previous section, it might appear that there is no benefit to a naturally aspirated engine. Forced induction solutions outclass those engines in everyway. If we are speaking about performance, then that is true, if you had two engines of identical size the forced induction would out-perform the naturally aspirated one every time.
The reason that many people prefer naturally aspirated engines is for their simplicity. A forced induction set-up has far more moving parts and potential points of failure than a naturally aspirated set-up. For example, with a turbocharged engine, you would need to have additional oil lines feeding the turbochargers, perhaps an oil cooler, an intercooler and additional piping for the both the exhaust and intakes. On top of all that, the turbochargers themselves will wear out as time goes on and need to be replaced, which further increases the maintenance cost. Similar logic can be applied to supercharged engines; however, it is worth noting that they typically have fewer points of failure than turbocharged set-ups. This allows a naturally aspirated engine to operate for longer with a far lower maintenance cost. If you had a forced induction set-up you would need to perform all the maintenance required for a naturally aspirated engine, and then the extra maintenance required for the forced induction components.
Most well built naturally aspirated engines can run for hundreds thousand kilometers with just oil changes, filter changes, and the occasional standard wear item replacement (take spark plugs for example). I drive a 2012 accord that has Honda’s legendary naturally aspirated K24 motor, my car has nearly 250,000km on it and all I do are regular oil changes and occasionally replacing wear items. My father drives a 2010 Mitsubishi Outlander that has a naturally aspirated V6 which has over 350,000km on it, the only maintenance done to that vehicle has been oil changes. This simply would not be possible with a forced induction set-up.
It is unfortunate that we are seeing the nearly the entire industry shift towards forced induction engines, this in largely due to the efficiency these engines can offer (delivering more power out of smaller engines). The Civic Si used to come with Honda’s naturally aspirated K24 that drivers loved, but newer models now come with a 1.5l turbocharged motor (the L15). The L15 is by no means a bad motor, and the Civic Si is by no means a bad car (I really want one myself), but this is just a sign of the industry changing. Some brands have turned to forced induction for its added performance, such as Dodge, Chevrolet and Ford in their top tier performance trims (the Hellcat, ZL1, ZO6 and GT500). But there are still some companies out there offering naturally aspirated motors, although Honda has taken the K24 away, the Pilot (click here to read my review of the Pilot) and Ridgeline continue to be offered with naturally aspirated V6 engines. A future garage that I would like to have for myself would be a Honda Civic Si and Pilot.
Final Thoughts
It may be somewhat sad, to learn how great naturally aspirated engines are for the vehicle owner and then immediately after, learn that the entire automotive industry is moving away from them. In this case, allow me to quote Vision (from Marvel): “A thing isn’t beautiful because it lasts.”, it is also true that time spent learning is not time wasted. I for one think that naturally aspirated engines will disappear entirely one day, but not within the next 5 years. So, when you’re shopping for your next vehicle, keep in mind the benefits of a naturally aspirated engine.
