What's the difference between a supercharger and a turbocharger?

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As engines get smaller and more efficient, manufacturers are looking to make the most out of their engines – and this is where superchargers and turbochargers come in.

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These two solutions are covered under a blanket term called ‘forced induction’.

Sometimes, you can purchase a new car with either option, and in extraordinary cases you can find an engine with both.

But what are they? How do they work? And which one is better? We look at the differences between a supercharger and a turbocharger.

How does forced induction work?

To understand how forced induction works, you must first understand the core fundamentals of an internal combustion engine – air, fuel, and spark.

On your car, you have an air intake that sucks clean air through a filter up to a throttle body. This throttle body contains a butterfly valve that lets the air slip through into what’s known as an intake manifold.

The intake side of the cylinder head releases a mixture of air and fuel into the engine. This is ignited by a spark plug, which forces a piston, and connecting rod, down in the cylinder.

On a four-stroke engine, which all modern ICE cars have, the piston does two different full rotations, or four strokes (two up and two down). The first is that mixture of fuel and air igniting.

The piston goes down the stroke and then back up again. On that second rotation (fourth stroke), it releases the exhaust gases out of the exhaust port side of the engine, down through the headers, and out the back of the exhaust pipe.

The movement of the piston up and down rotates the crankshaft, which is connected to several spinning parts between the engine and the driven wheels.

Of course, this is a simplified explanation, but these are the core fundamentals you need to know before we understand forced induction.

When forced induction is added, it compresses the air coming into the engine, which is known as ‘boost’. The forced induction provides the engine with more oxygen directed straight into the intake, which in turn means more fuel can be burnt, and more power can be made with a larger explosion of energy in the engine.

With that out of the way, what is the difference between a supercharger and a turbocharger?

How does a turbocharger work?

A turbocharger is the more common type of forced induction. At the core, it relies on exhaust gases to turn a turbine wheel, forcing more air into the engine.

As mentioned earlier, when your car engine is on its fourth stroke, it releases the gases that had built up from the explosion of the power stroke. These gases are wasted energy because they are propelled out of the exhaust pipe.

This is where the genius invention of the turbo comes in. It uses that otherwise wasted energy and turns it into added power.

Instead of headers, a turbo exhaust manifold is adapted to the exhaust side of the engine. The exhaust gases coming out turn a turbine, which is connected by a shaft to a propeller on the other side of the turbo.

The exhaust gases are expelled out the ‘dump’ of the turbo once they have turned the turbine.

The propeller side of the turbo has an inlet and an outlet hole. Because the propeller is already spinning due to the exhaust gases on the turbine, it creates an air vacuum through the inlet hole.

The air is then compressed by the propeller and either directly into the throttle body or through an intercooler that further cools the air before making its way into the engine.

This is where the term ‘forced induction’ comes from; the turbo is ‘forcing’ more air into the engine.

How does a supercharger work?

A supercharger is another type of forced induction; however, it works very differently from a turbocharger. Instead of using exhaust gases to spin a turbine, it uses the rotational forces of the engine to spin blades, creating compressed air that is forced into an intake.

The crankshaft in your engine spins a pulley. This pulley is connected to other auxiliary components on your engine, like an alternator that powers the car and charges the battery, an air-conditioning compressor, and a power steering pump that flows fluid to your steering rack.

The addition of a supercharger adds another component onto this belt-driven pulley system.

As the engine spins, it rotates the supercharger, which creates a vacuum to suck more atmospheric oxygen into it. The blades/rotors then compress the air and either send it through an intercooler for further cooling or directly to the throttle body and into the intake.

What's better, a supercharger or a turbocharger?

Now that we know the basics of a turbo and supercharger, what's the best option? Well, it depends heavily on what you are searching for.

In terms of fuel economy, a turbocharger will always be the better option because it turns wasted energy (expended exhaust gases) into usable energy, whereas a supercharger adds additional strain to the rotational forces of the engine, much like air-conditioning does.

Where the supercharger vs turbocharger battle becomes more of a personal preference is in the performance sector. Because a turbocharger relies on exhaust gases to ‘spool up’, it often has what is called ‘turbo lag’.

When chasing performance, a large turbo will often offer little-to-no performance at low engine speeds (RPM), meaning that there's often a lack of performance in the low revolution range but a sudden and aggressive spike once the engine gets moving.

On the other hand, a supercharger can instantly create boost because the compressor is running on a direct pulley from the engine. That means that a supercharger would be the best option for engines that require low RPM and linear power.

However, turbochargers have become a lot more technologically advanced and efficient, meaning that manufacturers can largely counteract the turbo lag by using a small ball-bearing turbo that ‘spools up’ quickly from a standstill as well as technology that keeps the turbine spinning even when the engine is not at high RPM.

Most of the time, turbocharged engines in economy cars (such as the Suzuki Swift, Volkswagen T-Cross, Nissan Qashqai) will not use the turbocharger to break power records, but instead use it to offer an average amount of power while boosting the performance of a small engine.

While these types of turbocharged engines require more fuel useage than if they weren't turbocharged, they win in terms of fuel efficiency compared to larger engines that generate the same amount of power without forced induction.

It is part of the reason we are now seeing medium SUVs, which historically would have something like a large V6, fitted with a 2.0-litre turbocharged four-cylinder, as well as hatchbacks fitted with turbocharged 1.0-litre engines.

While the turbocharger is more efficient, there are some manufacturers that have toyed with the possibility of using both a turbocharger and a supercharger.

Can a car have a turbocharger and a supercharger?

Yes, cars can have both turbochargers and superchargers; this is what is called ‘twincharged’. The idea actually came from an Italian rally car: the 1985 Group B Lancia Delta S4.

Technically, the Lancia Delta was the first road car to use this system, but in terms of mass production, Nissan was the first with its March Super Turbo in 1988.

Volkswagen, Seat, Audi, Skoda and Volvo are the only brands that use twin-charging in modern-day production.

The idea is to create an efficient engine by using the supercharger's benefit of low-down power combined with the turbocharger's benefit of generating power through the mid to high RPM.

But as turbochargers have become more efficient and hybrid power is more frequently used, twin-charging has become a less common application.

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