How Does A Supercharger Work?

How Does A Supercharger Work

Do you know a supercharger from a turbo charger? Or have you ever wondered how does a supercharger work? 

We’re going to look at all you need to know about superchargers, what they are, how they work and how many types there are. 

What Is A Supercharger?

A supercharger is either a mechanical or an electronic air compressor that forces more air into the combustion chamber. It does this by compressing air above atmospheric pressure without creating a vacuum. 

This forceful introduction of more air into the combustion chamber provides a boost to the engine as with the additional air more fuel is added to the charge and thus engine power is increased. 

An average 46% more horsepower and 31% more torque is achieved through using a supercharger in an engine. 

At high altitudes, engine performance deteriorates due to the low density and pressure of the air. A supercharger can help the engine to work at its optimum by delivering high pressure air. 

Superchargers produce power beyond what a naturally aspirated or turbo charged engine can achieve. 

How Does A Supercharger Work?

Let’s take a look at how the two types of supercharger actually work.

Mechanical Superchargers

Mechanical superchargers are typically belt driven but may also be driven by a shaft, a chain or gearing that is connected to the crankshaft of the engine (see also ‘How To Reset Crankshaft Position Sensor No Start‘). 

We’ll assume that we’re talking about a belt driven supercharger for the sake of this explanation. 

The belt runs on a pulley which can be altered to give more or less boost to the engine as the revolutions per minute (rpm) increase. In turn, the pulley rotates the shafts or screws in the supercharger. This then compresses the air which is going into the engine. 

In a centrifugal supercharger the belt is still driven by the engine but instead of rotating shafts or screws it turns a gear system. This gear system (see also ‘How To Use Paddle Shifters‘) then causes the turbine that compresses the air through centrifugal force, to turn. 

A supercharger differs from a turbo charger in that it will always require a physical link between it and the engine in order to provide the boost. 

Electrical Superchargers

Where an electrical supercharger is in use it will be in conjunction with a turbo charger. At low rpms, while the turbo builds boost the electric supercharger provides boost and response. 

When the turbo charger has reached its correct speed the electrical supercharger is bypassed. It does not need a physical link to the crankshaft of the engine in order to operate, unlike a mechanical supercharger. 

The only thing an electrical supercharger needs is a powerful electrical source. Typically vehicles with this technology have a 48 volt hybrid system and large alternators. 

Advantages & Disadvantages Of Superchargers

Advantages

A supercharger’s biggest advantage is that it delivers an instant boost unlike a turbo charger. This is because it is directly connected to and driven by the engine. As the rpms increase the degree of boost also increases, but this increase is more gradual than with a turbo charger.

Another advantage of a supercharger over a turbo charger is that it can operate with fewer auxiliary components.

Occasionally there is no need for the pipes that divert the pressurized air and in other cases there is also no need for an intercooler. This reduces the complexity and therefore the cost of the supercharger.  

Disadvantages

A big disadvantage of the supercharger over the turbo charger is that the former is inefficient compared to the latter. In some instances as much as 33% of the crankshaft’s power is needed to drive the supercharger. 

In addition, a supercharger is less thermally efficient than a turbo charger. This is because of the way a turbo charger works, by using energy from the exhaust that would otherwise be wasted. 

How Does A Supercharger Work (1)

Types Of Superchargers

There are three main types of mechanical supercharger. 

Roots Superchargers

The Roots supercharger is the oldest design, and it was first developed in 1860 for mine shaft ventilation by Philander and Francis Roots. But it was Gottlieb Daimler who applied the technology to automobiles. 

This design uses twin spinning rotors that mesh together and create pressure. Pockets of air between lobes on the rotors get compressed and send pressurized air through the intake manifold and then into the engine cylinders. 

These superchargers sit on top of the engine, occasionally protruding from the hood and are often seen on muscle cars or other souped up automobiles. 

Despite their macho image however, these are the least efficient supercharger only producing bursts of pressurized air rather than a consistent flow. They are also much heavier than other superchargers. 

Twin-Screw Superchargers

Although the twin-screw supercharger works in a similar fashion to the Roots supercharger it is more efficient. It still uses rotors, but they are more tapered which increases the pressure from the fill side to the discharge side of the housing. 

While it is more efficient than the Roots supercharger, it does cost more to manufacture due to tighter tolerances. 

Centrifugal Superchargers

The famous Louis Renault, who founded the French automobile company that still carries his name designed the first centrifugal supercharger in 1902. It was a departure from the Roots and twin-screw designs. 

An impeller, powered to 50,000-60,000 rpm draws air into the housing and centrifugal force causes it to radiate out from the center. The air is then passed through a diffuser, which is a series of vanes on the impeller, to pressurize it before it gets to the intake manifold. 

The advantages of a centrifugal supercharger are its low weight, compact size and the convenient positioning on the front of the engine. 

Final Thoughts

A supercharged engine has many advantages over a naturally aspirated engine with increased torque and horsepower being the most obvious. 

Of course the extra boost from a standing start in the city or on the open road is an added bonus and then there’s that racy sound! 

We hope you have enjoyed reading our guide to superchargers. 

Dave Oliver

Dave Oliver is a seasoned car modification expert with over twenty years of experience in the field. His knowledge spans from restoring vintage models to implementing the latest customization technologies. He brings his passion and expertise to life through informative and engaging articles.

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