How does a supercharger differ from a turbocharger?

Question

What is the difference between superchargers and turbochargers?

I looked it up before but I really don't understand what the difference is.

Answer 1

Both turbochargers and superchargers perform the same function: compress air that will be fed into the engine. In other words, they are glorified air compressors.

As with any compressor, both need energy in order to compress the air, which is where the difference between the two devices becomes relevant.

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Superchargers are belt-driven or chain-driven, so the compressor rotor is mechanically coupled to the rotation of the engine; when the engine rotates, the supercharger vanes rotate and compress air.

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Turbochargers use a completely different energy source - hot exhaust gases. The idea here is to make use of the hot gases to spin a turbine, which turns a shaft that turns the compressor vanes. As the hot exhaust gases perform work in turning the shaft, they cool down.

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The difference is concisely captured on this HowStuffWorks page:

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.

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Comparing the two...

Both technologies have their advantages and disadvantages; the "better" choice depends on a number of factors which include design philosophy, cost, available space, controller complexity and desired torque/power gains.

Having said that, there are plenty of "forced-induction" configurations out in the wild, ranging from single superchargers to twin-turbo and three-turbo (!) setups. In fact, some VW engines operate a turbocharger and a supercharger in tandem.

Answer 2

A turbo is a type of supercharger. Superchargers all compress the intake air before pushing it into the engine. A turbine-supercharger (aka "turbo") is powered by a turbine wheel connected to the exhaust. Other superchargers are driven via a pulley system directly from the engine.

That's all really. Conceptually speaking, a centrifugal supercharger and turbocharger are the closest in terms of performance and function. They both provide increasing levels of boost as RPM increases (within the limits of their efficiency). The only difference is that a centrifugal charger does not need to "spool up" because its speed is dictated by RPM, while a turbo's speed is dictated by the speed and volume of the exhaust gases, so there's a small amount of "lag" while the gases increase in proportion to how much boost is fed in.

Pro tip: it is possible to run some superchargers without installing an intercooler because they produce much less heat than a turbo. Although they eat a lot of torque in the process of increasing performance, so they are less efficient than turbos and will be worse for fuel consumption.