When it comes to high performance engine upgrades, the goal is to get as much power as possible from the engine while at the same time maintaining or increasing the efficiency of the engine. One upgrade that will boost the engine’s output is a supercharger. Superchargers are basically air compressors that force compressed oxygen into the air intake of a combustion engine. The added oxygen burns more fuel per engine cycle which in turn increases the output power. Superchargers are powered mechanically by the engine’s crankshaft via a belt, gear, chain, or shaft or by axial or radial gas turbines. There are two main types of superchargers that are added to high performance engines; positive displacement and dynamic.
The difference between the two types of superchargers is in the method of air compression. The first type is positive displacement. Positive displacement superchargers deliver pressure at a constant, almost fixed rate at all speeds and are normally mechanically powered. The air is divided within the supercharger and deposited bit by bit into the engine. Positive displacement superchargers have four main types of pumps; Roots, Lysholm twin-screw, sliding vane, and scroll-type supercharger or G-Lader. The pumps break down further into external and internal compression pumps.
Roots superchargers have external compression pumps. These pumps allow the pressure in the intake manifold to overcome the pressure coming from the supercharger which causes pressure to backflow into the supercharger. The backflow pressure is what compresses the gas power. These pumps are not as efficient as internal compression but are efficient in moving air at low pressure differentials.
The other types of positive displacement pumps use internal compression to some extent. Internal compression pumps compress the air within the supercharger and deposit it into the engine smoothly at a fixed compression ratio. The compression ratio should favor the supercharger because if the boost pressure of the engine exceeds the compression pressure of the supercharger, backflow will occur that takes away from the efficiency of the engine. Internal compression superchargers should match or exceed the pressure of the engine for maximum efficiency.
The other type of superchargers is dynamic compressors. Unlike positive displacement superchargers, dynamic compressors deliver higher pressure at higher speeds and are normally powered by gas turbines. They excite the air to a high rate and exchange the speed with the engine for air pressure. Therefore, the more pressure within the engine, the more air velocity the supercharger will produce to exchange with the engine.
Superchargers and turbochargers both work to increase the power output of an engine but are powered differently. The main difference is that superchargers are powered directly by the engine while turbochargers are powered by the exhaust from the engine. Turbochargers can gain more power and higher fuel efficiency than superchargers but superchargers have higher throttle response and can reach top speeds faster. This is because turbochargers feed off of the exhaust which is not strong enough at first to power a turbocharger until it reaches a high RPM. When the exhaust is strong enough to start the turbocharger, the boost causes even more exhaust to give the turbocharger more power, causing a sudden surge in speed and power output after a slow start. Turbochargers do not apply boost in proportion to the RPM like superchargers.
Adding a supercharger to a high performance engine is a good way to boost its output power. The engine- driven nature of the supercharger allows it to reach top speed faster and more smoothly than a turbocharger. Superchargers also work more efficiently when they have a higher pressure ratio than the engine. Talk to an aftermarket automotive technician about the best way to upgrade your high performance engine with a supercharger.
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