Since the invention of the internal combustion engine, automotive engineers, speed junkies and racecar designers 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. Another way to add power is to make a normal-sized engine more efficient. Adding a supercharger is a great way to achieve forced air induction. In this article, this explain what superchargers are, how they work and how they compare to turbochargers.
SUPERCHARGER SYSTEM
A supercharger is any device that pressurizes the air intake to above atmospheric pressure. Both superchargers and turbochargers do this. In fact, the term “turbocharger” is a shortened version of “turbo-supercharger,” its official name. 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.
There are two main types of superchargers defined according to the method of compression which is positive displacement and dynamic compressors. The former deliver a fairly constant level of pressure increase at all engine speeds (RPM), whereas the latter deliver increasing pressure with increasing engine speed.
Positive Displacement
Positive-displacement pumps deliver a nearly fixed volume of air per revolution at all speeds (minus leakage, which is almost constant at all speeds for a given pressure, thus its importance decreases at higher speeds). The device divides the air mechanically into parcels for delivery to the engine, mechanically moving the air into the engine bit by bit.
Dynamic Compressor
Dynamic compressor refers to pumps that transfer air at ambient pressure into the engine. If the engine is running under boost conditions, the pressure in the intake manifold is higher than that coming from the supercharger. That causes a backflow from the engine into the supercharger until the two reach equilibrium. It is the backflow that actually compresses the incoming gas. This is a highly inefficient process, and the main factor in the lack of efficiency of Roots superchargers when used at high boost levels. The lower the boost level the smaller is this loss, and Roots blowers are very efficient at moving air at low pressure differentials, which is what they were first invented for (hence the original term “blower”).
SUPERCHARGER VS TURBOCHARGER
[youtube:http://www.youtube.com/watch?v=Hv3SfYuWH5g 425 344]
TURBOCHARGER SYSTEM
One of the surest ways to get more power out of an engine is to increase the amount of air and fuel that it can burn. One way to do this is to add cylinders or make the current cylinders bigger. Sometimes these changes may not be feasible, a turbo can be a simpler, more compact way to add power, especially for an aftermarket accessory.
A turbocharger, or turbo is a centrifugal compressor powered by a turbine that is driven by an engine’s exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine which isforced induction, thereby resulting in greater performance. Turbochargers allow an engine to burn more fuel and air by packing more into the existing cylinders.
The advantage of compressing the air is that it lets the engine squeeze more air into a cylinder, and more air means that more fuel can be added. Therefore, you get more power from each explosion in each cylinder. A turbocharged engine produces more power overall than the same engine without the charging. This can significantly improve the power to weight ratio for the engine.
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