What is a turbocharger?

When it comes to combining performance with reduced fuel consumption, engineers are almost forced to opt for a turbo engine.

Outside the thin air of the supercar world, where Lamborghini still insists that naturally aspirated engines remain the cleanest and most Italian way to produce power and noise, the days of non-turbocharged cars are coming to an end.

It is impossible, for example, to get a naturally aspirated Volkswagen Golf. After Dieselgate, of course, this is unlikely to matter, because no one wants to play golf anymore.

However, the fact remains that city cars, family cars, grand tourers and even some supercars are leaving the ship in favor of a scuba future. From the Ford Fiesta to the Ferrari 488, the future belongs to forced induction, partly because of emissions laws, but also because the technology has evolved by leaps and bounds.

This is a case of small engine fuel economy for smooth driving and big engine power when you want it.

When it comes to combining higher performance with lower fuel consumption, engineers are almost forced to design their latest engines with turbocharged technology.

How can a turbo do more with less?

It all comes down to how the engines work, so let's talk a bit about the technique. For gasoline engines, the 14.7:1 air-fuel ratio ensures complete combustion of everything in the cylinder. Any more juice than this is a waste of fuel.

In a naturally aspirated engine, the partial vacuum created by the descending piston draws air into the cylinder, using the negative pressure inside to draw air in through the intake valves. It's an easy way to do things, but it's very limited in terms of air supply, like a person with sleep apnea.

In the turbocharged engine, the rule book has been rewritten. Instead of relying on the vacuum effect of a piston, a turbocharged engine uses an air pump to push air into a cylinder, just like a sleep apnea mask pushes air up your nose.

Although turbochargers can compress air at up to 5 bar (72.5 psi) above standard atmospheric pressure, in road cars they typically operate at a more relaxed pressure of 0.5 to 1 bar (7 to 14 psi) .

The practical result is that at 1 bar of boost pressure, the engine receives twice as much air as if it were naturally aspirated.

This means the engine control unit can inject twice as much fuel while maintaining an ideal air-fuel ratio, creating a much larger explosion.

But that's only half of the turbocharger's tricks. Let's compare a 4.0-liter naturally aspirated engine and a 2.0-liter turbocharged engine with a boost pressure of 1 bar, assuming that they are otherwise identical in terms of technology.

The 4.0-liter engine consumes more fuel even at idle and under light engine load, while the 2.0-liter engine consumes much less. The difference is that at wide open throttle, a turbocharged engine will use the maximum amount of air and fuel possible - twice as much as a naturally aspirated engine of the same displacement, or exactly the same as a naturally aspirated 4.0-liter.

This means the turbocharged engine can run anywhere from a meager 2.0 liters to a powerful four liters thanks to forced induction.

So it's a case of small engine fuel economy for gentle driving and big engine power when you want it.

How smart is that?

As befits an engineering silver bullet, the turbocharger itself is ingenious. When the engine is running, the exhaust gases pass through the turbine, causing it to spin at incredible speeds - typically between 75,000 and 150,000 times per minute.

The turbine is bolted to the air compressor, which means that the faster the turbine spins, the faster the compressor spins, sucking in fresh air and forcing it into the engine.

The turbo works on a sliding scale, depending on how hard you press the gas pedal. At idle, there isn't enough exhaust gas to get the turbine up to any meaningful speed, but as you accelerate, the turbine spins up and provides boost.

If you push with your right foot, more exhaust gases are produced, which compress the maximum amount of fresh air into the cylinders.

So what's the catch?

There are, of course, several reasons why we don't all drive turbocharged cars for years, starting with complexity.

As you can imagine, building something that can spin at 150,000 RPM day after day for years without exploding is not easy, and it requires expensive parts.

Turbines also require a dedicated oil and water supply, which puts more stress on the engine's lubrication and cooling systems.

As the air in the turbocharger heats up, manufacturers also had to install intercoolers to lower the temperature of the air entering the cylinder. Hot air is less dense than cold air, negating the benefits of a turbocharger and can also cause damage and premature detonation of the fuel/air mixture.

The most infamous shortcoming of turbocharging is, of course, known as lag. As stated, you need to accelerate and create an exhaust to get the turbo to start producing meaningful boost pressure, which meant that early turbo cars were like a delayed switch - nothing, nothing, nothing, EVERYTHING.

Various advances in turbo technology have tamed the worst of the slow-moving characteristics of early turbocharged Saabs and Porsches, including adjustable vanes in the turbine that move based on exhaust pressure, and lightweight, low-friction components to reduce inertia.

The most exciting step forward in turbocharging can only be found – at least for now – in F1 racers, where a small electric motor keeps the turbo spinning, reducing the time it takes to spin it up.

Similarly, in the World Rally Championship, a system known as anti-lag dumps the air/fuel mixture directly into the exhaust ahead of the turbocharger. Exhaust manifold heat causes it to explode even without a spark plug, creating exhaust gases and keeping the turbocharger boiling.

But what about turbodiesels?

When it comes to turbocharging, diesels are a special breed. This is really a hand in hand case, because without forced induction, diesel engines would never be as common as they are.

Naturally aspirated diesels can provide decent low-end torque, but that's where their talents end. However, with forced induction, diesels can capitalize on their torque and enjoy the same benefits as their gasoline counterparts.

The diesel engines are built by Tonka Tough to handle the enormous loads and temperatures contained within, meaning they can easily handle the extra pressure of a turbo.

All diesel engines - naturally aspirated and supercharged - operate by burning fuel in excess air in a so-called lean combustion system.

The only time naturally aspirated diesel engines come close to the "ideal" air/fuel mixture is at full throttle when the fuel injectors are wide open.

Because diesel fuel is less volatile than gasoline, when it is burned without much air, a huge amount of soot, also known as diesel particulates, is produced. By filling the cylinder with air, turbodiesels can avoid this problem.

So, while turbocharging is an amazing improvement for gasoline engines, its true flip saves the diesel engine from becoming a smoky relic. Although "Dieselgate" in any case can cause this to happen.

How do you feel about the fact that turbochargers find their way into almost all four-wheeled vehicles? Tell us in the comments below.