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Tuesday, January 1, 2019

Automobile Superchargers

Hello Everyone,
Wishing you a very warm and prosperous New year 2019. Keep safe driving.
Welcome to 1st article of 2019.

Everyone loves to drive car and often we dream to extract more and more juice from our Beast. Some times we do some after market modifications and some ECU remapping but it is not sufficient.
Since the invention of the internal com­bustion engine, automotive engineers, speed freakies and racecar drivers have been searching for ways to boost its power. ­One way to add power is to build a bigger engine. But bigger engines, which weigh more and cost more to build and maintain, are not always better option.
Another way to add power is to make a normal-sized engine more efficient. You can accomplish this by forcing more air into the combustion chamber. More air means more fuel can be added, and more fuel means a bigger explosion and greater horsepower. Adding a supercharger is a great way to achieve forced air induction. In this article, we'll explain what superchargers are, how they work and how they compare to turbochargers.
The difference between the two devices is their source of energy. Turbochargers are powered by the mass-flow of exhaust gases driving a turbine. Superchargers are powered mechanically by belt or chain-drive from the engine's crankshaft.

An ordinary four-stroke engine dedicates one stroke to the process of air intake. There are some important steps in this process:
Suction, Compression, Expansion and Exhaust
The piston moves down.
This creates a vacuum.
Air at atmospheric pressure is sucked into the combustion chamber.
Once air is drawn into the engine, it must be combined with fuel to form the charge a potential energy that can be turned into useful kinetic energy through a chemical reaction known as combustion. The spark plug initiates this chemical reaction by igniting the charge. As the fuel undergoes oxidation, a great deal of energy is released. The force of this explosion, concentrated above the cylinder head, drives the piston down and creates a reciprocating motion that is eventually transferred to the wheels.

Getting more fuel into the charge would make for a more powerful explosion. But you can't simply pump more fuel into the engine because an exact amount of oxygen is required to burn a given amount of fuel. This chemically correct mixture -- 14 parts air to one part fuel -- is essential for an engine to operate efficiently. The bottom line: To put in more fuel, you have to put in more air.

That's the job of the supercharger. Superchargers increase intake by compressing air above atmospheric pressure, without creating a vacuum. This forces more air into the engine, providing a "boost." With the additional air in the boost, more fuel can be added to the charge, and the power of the engine is increased. Supercharging adds an average of 46 percent more horsepower and 31 percent more torque. In high-altitude situations, where engine performance deteriorates because the air has low density and pressure, a supercharger delivers higher-pressure air to the engine so it can operate optimally.

Unlike turbochargers, which use the exhaust gases created by combustion to power the compressor, superchargers draw their power directly from the crankshaft. Most are driven by an accessory belt, which wraps around a pulley that is connected to a drive gear. The drive gear, in turn, rotates the compressor gear. The rotor of the compressor can come in various designs, but its job is to draw air in, squeeze the air into a smaller space and discharge it into the intake manifold.

To pressurize the air, a supercharger must spin rapidly -- more rapidly than the engine itself. Making the drive gear larger than the compressor gear causes the compressor to spin faster. Superchargers can spin at speeds as high as 50,000 to 65,000 rotations per minute (RPM). As it spins fast at such high rpms it is able to add 50% more air than atmospheric air pressure.

As the air is compressed, it gets hotter, which means that it loses its density and can not expand as much during the explosion. This means that it can't create as much power when it's ignited by the spark plug. For a supercharger to work at peak efficiency, the compressed air exiting the discharge unit must be cooled before it enters the intake manifold. The intercooler is responsible for this cooling process. Intercoolers come in two basic designs: air-to-air intercoolers and air-to-water intercoolers. Both work just like a radiator, with cooler air or water sent through a system of pipes or tubes. As the hot air exiting the supercharger encounters the cooler pipes, it also cools down. The reduction in air temperature increases the density of the air, which makes for a denser charge entering the combustion chamber.

Supercharger Advantages

The biggest advantage of having a supercharger is the increased horsepower. Attach a supercharger to an otherwise normal car or truck, and it will behave like a vehicle with a larger, more powerful engine.

Superchargers do not suffer lag -- a term used to describe how much time passes between the driver depressing the gas pedal and the engine's response. Turbochargers suffer from lag because it takes a few moments before the exhaust gases reach a velocity that is sufficient to drive the impeller/turbine. Superchargers have no lag time because they are driven directly by the crankshaft. Certain superchargers are more efficient at lower RPM, while others are more efficient at higher RPM. Roots and twin-screw superchargers, for example, provide more power at lower RPM. Centrifugal superchargers, which become more efficient as the impeller spins faster, provide more power at higher RPM.

Installing a turbocharger requires extensive modification of the exhaust system, but superchargers can be bolted to the top or side of the engine. That makes them cheaper to install and easier to service and maintain.

Superchargers are common additions to the internal combustion engines of airplanes. This makes sense when you consider that airplanes spend most of their time at high altitudes, where significantly less oxygen is available for combustion. With the introduction of superchargers, airplanes were able to fly higher without losing engine performance.

Supercharger Disadvantages

The biggest disadvantage of superchargers is they reduce your mileage but fir speed and performance lovers this would not be a concern and supercharger have also their defining characteristic: Because the crankshaft drives them, they must steal some of the engine's horsepower. A supercharger can consume as much as 20 percent of an engine's total power output. But because a supercharger can generate as much as 40-50 percent additional horsepower.

Supercharging puts an added strain on the engine, which needs to be strong to handle the extra boost and bigger explosions. Most manufacturers account for this by specifying heavy-duty components when they design an engine intended for supercharged use. This makes the vehicle more expensive. Superchargers also cost more to maintain, and most manufacturers suggest high-octane premium-grade gas.

Despite their disadvantages, superchargers are still the most cost-effective way to increase horsepower. Superchargers can result in power increases of 50 to 100 percent, making them great for racing, towing heavy loads or just adding excitement to the typical driving experience.


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