As a keen motorist, you’ve probably come across the terms “turbocharged” and “naturally aspirated” in regard to car engines at some point in your career. When it comes to the details, however, few can understand and explain the differences between them. Today, we are going to set things straight.
The history of the turbosupercharger
You probably wouldn't believe it, but the first series-production cars equipped with superchargers rolled out from the Mercedes-Benz factory as early as the 1920s. At that time, the device was called the compressor (Mercedes retained that name) and offered an astonishing output of 65 horsepower. Other automotive companies implemented it too, and soon Fiat, Alfa Romeo and Bentley could offer a vehicle with boosted power to their customers.
Despite these vehicles being fast, they were also unreliable. On top of that, the technology was relatively new, complex and thus incredibly expensive. Companies had to abandon mass production, and superchargers were only available for those who could cough up a small fortune to buy a high-performance vehicle. Until the end of the 20th century, the majority of cars used non-turbo propulsion.
How do turbochargers and naturally aspirated engines work?
For turbochargers, the modus operandi is simple. The engine starts, exhaust gases power a turbine that sucks the air from the outside of the car and pushes it inside the motor. This is called forced induction. With more compressed air inside the cylinders, fuel combustion is more efficient. In naturally aspirated powertrains, air is drawn into the engine’s cylinders as atmospheric pressure acts against a partial vacuum caused by the movement of pistons. To take full advantage of NA, a car needs to have a powerful engine that can facilitate this process.
The numbers say it all. Two decades ago, a 1.2L naturally aspirated petrol engine could produce about 60 horsepower. Nowadays, 1.2L turbocharged motors can reach even twice that number! Apart from the power output, the additional benefit is the flattened torque curve. It means that the full potential of the powertrain is available at lower crankshaft speeds, and lower crankshaft speeds mean better fuel economy.
Understanding the difference between a turbocharger and a supercharger
People use the two names interchangeably and in reality, the turbocharger is simply a type of supercharger that we can find in most internal combustion engine cars nowadays. While a turbocharger uses exhaust gases to spin a turbine that powers the compressor, a supercharger is powered directly by the engine itself. Air is drawn into the engine as the supercharger compresses it above atmospheric pressure. This eliminates “turbo lag”, a phenomenon in turbochargers caused by insufficient intake of air to spin the turbine that produces a delayed power boost. However, much like naturally aspirated engines, superchargers lack in the fuel efficiency department.
Some performance cars use twin-charge technology, a combination of an exhaust gas-powered turbocharger and a crankshaft-powered supercharger. Unfortunately, to call these eco-friendly would be an enormous misunderstanding, since they consume gigantic amounts of fuel and their exhaust gas emissions are far from what we consider clean in this day and age.
Did naturally aspirated engines fall from grace?
Naturally aspirated petrol and diesel engines dominated the automotive industry until the 1990s. The change came with the Kyoto Protocol that forced signatories to cut down on nitrogen and carbon oxides emissions. With the onset of the EURO I standard, car companies realised that diesel engines would no longer meet ecology requirements. EURO II, III and IV soon followed. They made the production of naturally aspirated diesel powertrains virtually impossible. By 2005, all the new diesel vehicles available on the market were powered by turbocharged motors. Petrol powertrains soon met the same fate.
The advancement in turbo technology allowed automotive companies to introduce smaller and lighter engines in favour of heavier, naturally aspirated versions. The benefits were obvious:
- reduced fuel consumption;
- reduced nitrogen and carbon oxides emissions;
- reduced weight of the car (especially with three-cylinder engines).
In 2021, it is quite rare to find a brand new vehicle with a naturally aspirated engine, with a few powerful exceptions such as the Audi R8 or the Lamborghini Aventador S. All countries that agreed to adopt the EURO norms have gradually phased them out in favour of turbocharged cars.
Naturally aspirated or turbocharged: which is better?
Turbochargers changed the automotive industry forever, offering better performance, efficiency and sprinkling a little eco-friendliness on top. Some motorists love them, while certain purists would probably love to see them discontinued.
This is because naturally aspirated engines last longer and are more reliable than their supercharged counterparts. Forced air engines work harder as they use higher compression and run hotter combustion chambers. Turbochargers are also lubricated and cooled by the same oil as the engine, leading it to break down at a quicker rate. This means more frequent oil changes. And, of course, more parts mean a bigger chance that something might break down.
But the rapid advancement in technology means that vehicles with boosted power are now more reliable than they ever were. And while you will likely appreciate the unique sound of your naturally aspirated engine, unless you’re an automobile purist, this feature is hardly dominant. Turbocharged cars excel in fuel economy and relative performance, offering drivers speed and acceleration that cannot be matched by naturally aspirated engines of the same size. Prepare to splash some cash on a bigger engine if you want to reap the benefits of naturally aspirated cars.
So, which do you prefer?