Supercharger is a familiar term in the ears of car enthusiasts. Although this forced induction method is not as popular as compared to its sibling, the turbocharger.
In the previous review, we have repeated the complete turbocharger. It feels incomplete if we also don’t discuss about the supercharger.
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 the supercharger.
Let’s just start. Prepare the coffee first hehe.
What is a Supercharger?
Supercharger is one method of forced induction in a car engine. Forced induction itself is the process of delivering compressed air to the engine intake which is then used in combustion of fuel in the combustion chamber. Other forced induction methods are turbochargers and nitrous oxide .
The biggest difference from the supercharger and turbo is the driving source of the compressor rotor. Turbocharger driving power comes from exhaust gas (exhaust), while the supercharger driving force is the crankshaft rotation on the engine (crankshaft). The crankshaft is the piston handle that rotates together with the ups and downs of the piston.
Same thing with the turbo, the purpose of the supercharger is to compress the intake air. The compressed compressed air naturally has greater oxygen content. With greater oxygen we can then increase the amount of fuel. The more oxygen and fuel burned, of course, the greater the energy produced.
How does the supercharger work?
As mentioned before, increasing the amount of fuel into the cylinder will also increase the power of the explosion when combustion. But we cannot do that without the right amount of oxygen. The right ratio for an engine to work efficiently is 14 air versus 1 fuel. So the more we add fuel the more air is needed for the combustion process.
This is the function of the supercharger. This device will force more air into and compress it so that it is denser. This device is able to add an average of 46 percent more horsepower and 31 percent more torque. On high altitudes, where engine performance deteriorates because air has low density and pressure, the supercharger can also provide higher pressure air to the engine so that it can operate optimally.
Unlike a turbocharger, which uses combustion exhaust gases to drive the compressor, the supercharger gets its power directly from the engine’s crankshaft. The supercharger is connected to the crankshaft via a belt, chain or gear which wraps the pulley. This pulley is then connected to the drive gear. The driving gear, in turn will rotate the rotor (compressor) gear. There are various designs of the compressor rotor shape, but its job is to draw air in, compress it and drain it into the intake manifold.
To compress the air, the supercharger must spin fast, even faster than the engine itself. The driving gear is made bigger than the compressor gear, causing the compressor to rotate faster. Superchargers can spin at speeds of 50,000 to 65,000 rotations per minute (RPM)!
The compressor rotates at 50,000 RPM which means there is a compression pressure of around 6-9 pounds per square inch (psi). That’s around 6-9 psi additional pressure from atmospheric pressure. Atmospheric pressure at sea level is 14.7 psi, so the typical push from the supercharger means about 50 percent more air into the engine.
When the 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 by a spark plug in combustion. Therefore, compressed air coming out of the exhaust unit must be cooled before entering the intake manifold. Intercooler is responsible for this cooling process.
There are three types of superchargers that are distinguished by the way and type of rotor to compress air. The three types are roots, twin-screw and centrifugal.
In essence, all types have the same function, namely compressing air to be then distributed to the intake manifold. But all three have advantages and disadvantages of each.
This type or type will be discussed in detail later. The short explanation is as follows.
- Roots. This type of supercharger is the longest design since 1860. Yes, 1860 there is already a supercharger hehe. Roots use two rotor stems that function like turbines. The two rotors are not connected to each other and move in opposite directions to the outside area or towards the supercharger wrapper wall. This makes the air sucked and moves towards the inner wall. This type of roots is often referred to as a blower because it functions to suck air and drain it on the intake manifold. Air compression does not occur on the supercharger but on the intake manifold.
- Twin screw. Just like roots, twin-screws use two rotors that are shaped like screws. Its 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 inhaled but also allows the compression process inside the supercharger.
- Centrifugal. This type is almost the same as a turbocharger. Not only from the form but the character and effectiveness also have in common. Centrifuges are shaped the same as turbo, aka snails. It’s just that in turbo we will see like two snails put together because it consists of two interconnected turbines. Well, there is only one conch in the Centrifugal Supercharger, because the driving force comes from the engine crankshaft.
Strengths and weaknesses
Just like a turbo, the main advantage of the supercharger is the addition of power without the need to enlarge or increase the number of engine cylinders. Likewise with the weaknesses that have some similarities with the turbocharger system.
For the advantages and disadvantages compared to turbo, later we will discuss more fully in the next review.
- Making combustion of the cylinder effective so that it increases power output without having to increase capacity or increase the number of engine cylinders. Intake of pressure (boost) from the supercharger is generally at 6-9 pounds per square inch (psi). Normal atmospheric pressure is 14.7 psi. So we can see 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% due to the level of work efficiency of the supercharger which is not perfect according to theory.
- By not increasing the capacity and number of engine cylinders, making the engine is not as heavy as a non-supercharger 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 (intake). This makes the rest of the exhaust gas lower pollution.
- The turbo system uses combustion exhaust gas. This results in a lag or delay between when we press the accelerator and when the turbo turbine fan starts actively working. In the supercharger, the driving force is the engine crankshaft so the compression process can be faster. This results in faster torque and throttle response compared to turbo.
- Along with intake of oxygen-rich air, the need for fuel for the combustion process also increases. This makes fuel consumption increase along with the increase in engine power. Besides turbochargers also require high octane fuel to prevent knocking on the engine.
- The reliability of the engine is reduced due to the turbocharger system making the engine more complex. The more complex the engine, the more components, the more the possibility / factor for damage to the engine.
- The turbo system makes the engine components work under high pressure and temperature. This makes engines with a turbo system often less durable than non-turbo (NA) engines.
- The driving force of the supercharger is the engine crankshaft so that it can be called this device stealing power from the engine. The amount of stolen power can reach 20% of engine power! This is why the supercharger has a parasitic character, giving the engine extra work load.
- Intercooler installation, especially on the types of roots and twin-screw is rather difficult.
Inventor and History
In closing, let us discuss a little about the history of supercharger technology.
Between the years 1848-1849, G. Jones of Birmingham, a British national, first introduced a compressor with a root type. This device he uses for the purpose of mine ventilator. Its function is as an air blower that circulates air for underground mining workers.
In 1860, the two brothers Philander and Francis Marion Roots, founder of the company Roots Blower of Connersville, Indiana, patented the design for air propulsion. This air compressor is used in processing machinery for mining products 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 internal combustion engines in 1885. Daimler was the founder of Daimler Motoren Gesellschaft which later became Mercedes-Benz.
Still in Germany, on March 24, 1878, Heinrich Krigar from Germany obtained a patent for the first screw-type compressor. In the same year on August 16 he obtained another patent after modifying and refining 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 are Mercedes 6/25/40 hp and Mercedes 10/40/65 hp. Both of these models were introduced in 1921 and have supercharger Roots.