What Is Supercharger?- Definition, Types And Working

A supercharger is an air compressor that increases the pressure of air supplied to an internal combustion engine. This aids in higher power output as the engine gets more oxygen in each of its intake cycles and helps it to burn more fuel.

Superchargers can be powered mechanically by means of a belt, shaft, or chain connected to the engine’s crankshaft. Two types of superchargers are available – positive displacement and dynamic compressors.

To define them in simple terms, the positive displacement superchargers deliver a constant level of pressure increase at all engine speeds (RPM). On the other hand, Dynamic Compressor superchargers do not deliver as much pressure at lower speeds but deliver exponential speed pressure above its threshold.

What is a Supercharger?

In an internal combustion engine, a supercharger compresses the intake gas, forcing more air into the engine in order to produce more power for a given displacement.

The current categorization is that a supercharger is a form of forced induction that is mechanically powered (usually by a belt from the engine’s crankshaft), as opposed to a turbocharger, which is powered by the kinetic energy of the exhaust gases.

However, up until the mid-20th century, a turbocharger was called a “turbosupercharger” and was considered a type of supercharger.

The first supercharged engine was built in 1878, with usage in aircraft engines beginning in the 1910s and usage in car engines beginning in the 1920s. In piston engines used by aircraft, supercharging was often used to compensate for the lower air density at high altitudes.

Supercharging is less commonly used in the 21st century, as manufacturers have shifted to turbochargers to reduce fuel consumption and increase power outputs.

Superchargers vs Turbochargers

This is one competition that can never derive a winner. This is because both these components are good in their own right and have a loyal fan base.

Deciding on which is better than the other can get political. Both these components have the same end result, and that is to feed the engine with more cool air. This, in turn, helps the engine to burn more fuel and produce more power as a result.

Turbochargers take advantage of the velocity and energy of exhaust gases expelled from the engine’s cylinders to spin the turbine which drives a small compressor to pump more air back into the engine.

On the other hand, a supercharger is powered mechanically by the engine via a belt that runs off the crankshaft or in some cases, an electric motor.

How does a supercharger work?

An internal combustion engine sucks air into a cylinder where it’s compressed, igniting a blend of fuel and air. Once ignited, it generates a power stroke of the piston before sending energy to the wheels.

When an engine’s displacement is relative to a vehicle’s design, it supplies a corresponding level of performance. When more power is needed, a larger engine will get the job done, but so will a forced induction system such as a supercharger.

Superchargers are belt-operated and most often powered by an engine’s crankshaft. This type of forced induction is different from a turbocharger, which utilizes waste heat from the exhaust.

When a supercharged car is running, the engine pulls air through the intake, hood scoops, and any other entry points. Next, the supercharger compresses the air which increases the air’s pressure and density.

This way the engine receives more air through the same intake, which allows it to burn more fuel resulting in a boost in performance.

However, that boost comes at an upfront cost. Notably, a loss of horsepower of as much as 20%.

On the other hand, a supercharger produces far more horsepower than the belt drive takes from the engine, thus the net increase in horsepower is somewhere between 30% and 50%.

Supercharger Diagram

Types of Supercharger

There are four main categories of superchargers for automotive use:

• Centrifugal Supercharger
• Root type supercharger
• Twin-screw Superchargers
• Vane type supercharger

#1. Centrifugal superchargers.

A centrifugal supercharger is a specialized type of supercharger that makes use of centrifugal force in order to increase the manifold air pressure, MAP. An increased MAP allows the engine to burn more fuel, which results in increased power output.

Centrifugal superchargers are generally attached to the front of the engine via a belt-drive or gear-drive from the engine’s crankshaft.

The centrifugal supercharger is used in many applications including, but not limited to, automotive, truck, marine, aircraft, motorcycles, and UTVs.

There are two types of Centrifugal superchargers:

• Automotive superchargers: Centrifugal superchargers have become popular in the aftermarket as a bolt-on addition to improve performance. By design, centrifugal superchargers allow for easy integration of air-to-air or air-to-water intercooling. Several companies build centrifugal superchargers and also offer them as complete systems which can be easily installed by a mechanic or the auto enthusiast at home.
• Aircraft superchargers: Because air pressure decreases with altitude, air compression helps maintain engine power as the aircraft climbs.

#2. Root’s type supercharger.

Root’s type contains two rotors of epicycloid shape. The rotors are of equal size inter-meshed & are mounted and keyed on 2 different shafts. Anyone shaft is powered by the engine via a V-belt or gear train(depending on the distance).

Each rotor can have 2 or more 2 lobes depending upon the requirement. The air enters through the inlet & gets trapped on its way to the outlet. As a result, pressure at the outlet would be greater than the inlet.

#3. Twin-screw Superchargers.

A twin-screw supercharger operates by pulling air through a pair of meshing lobes that resemble a set of worm gears. Like the Roots supercharger, the air inside a twin-screw supercharger is trapped in pockets created by the rotor lobes.

But a twin-screw supercharger compresses the air inside the rotor housing. That’s because the rotors have a conical taper, which means the air pockets decrease in size as air moves from the fill side to the discharge side. As the air pockets shrink, the air is squeezed into a smaller space.

This makes twin-screw superchargers more efficient, but they cost more because the screw-type rotors require more precision in the manufacturing process. Some types of twin-screw superchargers sit above the engine like the Roots supercharger.

They also make a lot of noise. The compressed air exiting the discharge outlet creates a whine or whistle that must be subdued with noise suppression techniques.

4. Vane type supercharger

A number of vanes are mounted on the drum of the supercharger. These vanes are pushed outwards via pre-compressed springs. This arrangement helps the vane to stay in contact with the inner surface of the body.

Now due to eccentric rotation, the space between two vanes is more at the inlet & less at the oulet. In this way, the quantity of air that enters the inlet decreases its volume on its way to outlet.

A decrease in volume results in an increment of the pressure of air. Thus the mixture obtained at the outlet is at a higher pressure than at the inlet.

Advantages of supercharging

• Higher power output
• Greater induction of charge mass
• Better atomization of fuel
• Better mixing of fuel and air
• Better scavenging products
• Better torque characteristics over whole range
• Quick acceleration of vehicle
• Complete and smooth combustion
• Even fuel with poor ignition quality can be used
• Improved cold starting
• Reduced exhaust smoke
• Reduced specific fuel consumption
• Increased mechanical efficiency
• Smooth operation and reduction in diesel knock tendency

Disadvantages of supercharging

• Increased detonation tendency in SI engines
• Increased thermal stress
• Increased heat loss due to increased turbulence
• Increased gas loading
• Increased cooling requirements of the engine

FAQs.