Intercooling
An unavoidable side-effect of forced induction is that compressing air, as stated in the first law of thermodynamics, raises its temperature . As a result, the charge density is reduced and the cylinders receive less air than the system’s boost pressure prescribes. The risk of detonation, or "knock", greatly increases. These drawbacks are countered by charge-air cooling, which passes the air leaving the turbocharger or supercharger through a heat exchanger typically called an intercooler. This is done by cooling the charge air with an ambient flow of either air (air-air intercooler) or liquid (liquid-to-air intercooler). The charge air density is increased and the temperature is reduced. In this way an intercooler can greatly increase the ability to run higher absolute compression ratios and take full advantage of using compressors in series. The only drawback of intercooling is its mass and volume of the cooler along with the associated plumbing and piping.
Read more about this topic: Forced Induction