Supercharger

Supercharger

Supercharger is a term that is familiar to car enthusiasts. Although the forced induction method is not as popular as its sibling, the turbocharger.

In this review, we will discuss what a supercharger is and how it works. Not only that, we will also discuss the components, types / types, and also the advantages and disadvantages of superchargers.

Supercharger is a method of forced induction in car engines. Forced induction itself is the process of flowing compressed air to the engine intake which is then used to burn fuel in the combustion chamber. Other forced induction methods are turbochargers and nitrous oxide .

The biggest difference between a supercharger and a turbo is the source of the driving force for the compressor rotor. The turbocharger's propulsion comes from exhaust gases (exhaust), while the supercharger's propulsion is the crankshaft rotation of the   engine (crutches). The crankshaft is a piston grip that rotates along with the rise and fall of the piston.

As with the turbo, the purpose of the supercharger is to compress the intake air. The compressed air certainly has a higher oxygen content. With greater oxygen we can then increase the amount of fuel. The more oxygen and fuel that is burned, of course, the greater the power produced.

How Do Superchargers Work?

As mentioned earlier, increasing the amount of fuel into the cylinder will also increase the explosive power during combustion. But we can't do that without the right amount of oxygen. The correct ratio for the engine to run efficiently is 14 air to 1 fuel. So the more we add fuel, the more air is needed for the combustion process.

This is where the function of the supercharger. This device will force more air in and compress it so that it is denser. This device is capable of adding an average of 46 percent more horsepower and 31 percent more torque. At high altitudes, where engine performance deteriorates because the air has a low density and pressure, the supercharger can also deliver higher pressure air to the engine so that it can operate optimally.

Unlike turbochargers, which use combustion exhaust gases to drive the compressor, superchargers get their power directly from the crankshaft of the engine. The supercharger is connected to the crankshaft via a belt, chain or gear that wraps around the pulley. This pulley is then connected to the drive gear. The drive gear, in turn, will rotate the rotor (compressor) gear. There are various designs of compressor rotor shapes, but their job is to draw air in, condense it and circulate it into the intake manifold.

To compress the air, the supercharger must spin fast, even faster than the engine itself. The drive gear is made larger than the compressor gear, causing the compressor to rotate faster. The supercharger can spin at a speed of 50,000 to 65,000 rotations per minute (RPM)!

The compressor rotates at 50,000 RPM this means there is a compression pressure of about 6-9 pounds per square inch (psi). That's about 6-9 psi additional pressure from atmospheric pressure. Atmospheric pressure at sea level is 14.7 psi, so the typical boost from the supercharger means about 50 percent more air into the engine.

When air is compressed, it gets hotter, which means it loses its density and is less able to expand during an explosion. The air will be less effective to be blown up by the spark plug on combustion. Therefore, the compressed air leaving the exhaust unit must be cooled before entering the intake manifold. The intercooler is responsible for this cooling process.

Supercharger Types

There are three types of superchargers that are distinguished by the way and type of rotor to compress the air. The three types are roots, twin-screw, and centrifugal.

In essence, all types have the same function, namely to compress air and then channel it to the intake manifold. But all three have their advantages and disadvantages.

This type or type will be discussed in detail later. The brief explanation is as follows.

1.      Roots. This type of supercharger is the oldest design since 1860. Yes, the 1860 already has a supercharger, you know hehe. Roots uses two rotor rods that function like turbines. The two rotors are disconnected from each other and move in opposite directions towards the outer area or towards the wall of the supercharger case. This causes the air to be sucked in and move towards the inner wall. This type of roots is often referred to as a blower because its function is to suck air and drain it into the intake manifold. Air compression does not occur in the supercharger but in the intake manifold.

2.      Twin screw. Just like roots, twin-screw uses two rotors that are shaped like screws. The size is slimmer than the roots supercharger. The two rotors move in opposite directions to the inner or middle area of ​​the supercharger. This not only makes the air sucked but also allows the compression process in the supercharger.

3.      Centrifugal. This type is almost the same as a turbocharger. Not only from the shape but the character and effectiveness also have similarities. Centrifugal shaped like a turbo alias like a snail. It's just that on the turbo we will see like two snails put together because it consists of two interconnected turbines. Well, in this Conch Centrifugal Supercharger there is only one, because the driving force comes from the crankshaft of the engine.

Advantages and disadvantages

Just like a turbo, the main advantage of a supercharger is the addition of power without the need to enlarge or increase the number of engine cylinders. Likewise with the weakness that has some similarities with the turbocharger system.

For the advantages and disadvantages compared to the turbo, we will discuss it more fully in the next review.

Advantages

Streamlining combustion in the cylinders so as to increase output power without having to increase the capacity or increase the number of engine cylinders. Intake pressure (boost) from the supercharger is generally 6-9 pounds per square inch (psi). Normal atmospheric pressure is 14.7 psi. So we can see that there is about 50% more air entering the engine. This means a 50% increase in power, although in reality the increase is usually 30-40% because the supercharger's efficiency level is not perfect according to theory.

By not increasing the capacity or number of engine cylinders, the engine is not as heavy as a non-supercharged engine with the same power. This engine load affects the weight of the vehicle which then affects fuel efficiency.

This system allows better combustion through more oxygen content in the intake air. This makes the remaining exhaust gases less polluting.

The turbo system uses combustion exhaust gas propulsion. This results in a lag or delay between when we press the gas pedal and when the turbo turbine fan starts to actively work. In the supercharger, the driving force is the engine crankshaft so that the compression process can be faster. This results in a more instant torque and throttle response than a turbo.

Deficiency

As the intake air is richer in oxygen, the need for fuel for the combustion process also increases. This makes fuel consumption increase along with the increase in engine power. In addition, the turbocharger also requires high octane fuel to prevent engine knocking.

Engine reliability is reduced because the turbocharger system makes the engine more complex. The more complex the machine, the more components, the more possibilities/factors for the occurrence of damage to the machine.

The turbo system makes engine components work under high pressure and temperature. This makes engines with turbo systems often not as durable as non-turbo (NA) engines.

The driving force of the supercharger is the crankshaft of the engine so it can be called this device stealing power from the engine. The amount of power stolen can reach 20% of the engine power! This is why the supercharger has a parasitic character, meaning it gives an additional workload on the engine.

Intercooler installation, especially on roots and twin-screw types, is a bit difficult to do.

Inventors and History



 In closing, let us discuss a little about the history of supercharger technology.

Between 1848-1849, the British G. Jones of Birmingham first introduced a compressor with a roots type. He uses this device for mine ventilators. Its function is as an air blower that circulates air for mining workers underground.

In 1860, brothers Philander and Francis Marion Roots, founders of the Roots Blower company of Connersville, Indiana, patented a design for air propulsion. These air compressors are used in mining processing machinery and other industrial applications.

Well, testing the world's first functional supercharger engine was made by an engineer named Dugald Clerk from Scotland. He used it for the first 2 stroke engine in 1878. In Germany,  Gottlieb Daimler received a German patent for supercharging an internal combustion engine in 1885. This Daimler was the founder of the Daimler Motoren Gesellschaft which later became Mercedes-Benz.

Still in Germany, on March 24, 1878, Heinrich Krigar of Germany obtained a patent for the first screw-type compressor. In the same year on August 16 he obtained another patent after modifying and improving the initial design. The latest design shows two rotors with each rotor having the same shape as the other.

Then in 1902, Louis Renault, who was one of the founders of Renault, patented a centrifugal type supercharger in France.

The first cars produced in the world with a supercharger were the Mercedes 6/25/40 hp and the Mercedes 10/40/65 hp. Both models were introduced in 1921 and had a Roots supercharger.

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