Engine and exhaust create the majority of heat in your vehicle and intercooling removes that heat.
It is not unusual to net an 85° - 200° drop in intake air temperature (depending on application). This temperature drop results in a denser thus more powerful air/fuel ratio, it greatly reduces the chances of detonation or pre-ignition, and virtually eliminates the decrease in power sometimes felt in back-to-back runs and extended pulls in non intercooled setups.
A reduction in temperature allows your timing to be tuned to factory (or close to factory) timing, and avoids substantial horsepower loss produced by excessively retarding ignition timing.
Intercooling systems basically function as a passive waste gate. This flattens the boost curve at higher rpm's, allowing increased boost to be tuned for at lower rpm's.
Allowing for full timing of your forced induction setup keeps the engine pulling through redline and reduces high rpm fall off vs. non intercooled supercharger systems.
Benefits of Intercooling are felt at any boost level. The true result of these benefits the ability to safely run considerably higher boost levels than non-intercooled supercharger systems.
Detonation, or engine knock, occurs when fuel ignites before the piston reaches its scheduled spark ignition. To learn more see our article on what detonation is and how it can be avoided?
Both air-to-air and air-to-water intercooler systems are available and their usage guidelines are fairly straightforward.
Air-to-air intercooler technology is often chosen for street applications because it is easy to install, highly effective, reliable (it has no moving parts), and requires no maintenance. Air-to-water intercooler systems have a higher level of installation difficulty because they contain an intercooler, a separate radiator to cool the water, a water tank, and a pump. The biggest drawback for air-to-water intercooler systems in street applications is the requirement of ice addition at regular intervals in order to match the efficiency of air-to-air technology. Thus the requirement of ice and the possibility of pump failure or leakage mean that air-to-water is less reliable. For race-only applications, however, air-to-water is often chosen and works well. The need to add ice at the track prior to each run is not a big drawback.