Though both are, fundamentally, trying to achieve the same in goal (namely to force more air into a combustion chamber so that more fuel can be added, creating a bigger “boom” and more power), the two differ in how they go about doing it.

A supercharger is driven directly by the motor, typically through a belt, and as such is akin to any motor ancillary. Like a water pump, or alternator, its directly driven nature provides instant reaction to rpm changes. It's always running, and therefore always pumping, positive displacement nature ensures that when one steps on the gas, it pumps air immediately and without hesitation. That same direct drive response however provides its biggest drawback, it is always being spun by the motor, and is therefor scavenging power from the motor itself to drive it.

Though supercharging has typically been associated with low-rpm grunt that flattens out with revs, that is not universally applicable. The development of Lysholm twin screw superchargers has broadened the usability of the supercharger, and other types like the centrifugal supercharger are in fact better at higher rpm running than low.

The development of clutch system like those of Mercedes allow the supercharger to be disengaged as well, preventing it from always drawing power from the motor.

Turbochargers draw their power from exhaust gases. An impeller placed in the exhaust stream is spun by exhaust gases which in tern spins another impeller that pumps air into the motor. This is considered a more efficient system because it is putting to use exhaust gases that would have otherwise done nothing.

This prove advantages for small motor, like the ones in Europe, that would cannot afford to have what little power they have lessened by being taken by a supercharger.

Disadvantages are that the motor must first produce enough gas to spin the impeller, so if the wrong sized turbo is used for the application, there is delay before it can pump enough air to create meaningful power. Hence the term “turbo-lag.”

Again, like superchargers, developments have seen many of disadvantages disappear, and many of the advantages produce more and even be even more advantageous.

Ultimately, the biggest factor in these times is likely to be packaging since the two systems have been developed to the point that they are very close in terms of both advantages and drawbacks; and in that respect turbocharges typically have the advantage with their smaller easier to package nature.


via Automobile Magazine