An intercooler (sometimes referred to as an aftercooler) is designed to remove heat from the compressed air coming from the supecharger (or turbo) before it enters the engine's induction system. An intercooler works just lie a radiator - air is cooled by fins, bars, louvres, and plates inside the intercooler that are cooler than the compressed air coming from the supercharger. The reduction in air temperature increases the density of the air (more air molecules per cupic foot), which consequently increases your engine's ability to make more horsepower and torque. The decreased air temperature allows you to run more boost on a given octane of fuel before detonation occurs..

There are several important benefits to intercooling that have resulted in their increased popularity in recent years. The most significant advantage is that intercooling increases the detonation threshhold because of the cooler air charge, meaning you can run more ignition advance for higher performance, or run lower octane fuel before experiencing detonation. This makes intercoolers very desirable for those looking to get the most out of their street vehicles on pump gasoline. The cooler air also allows your engine to run slightly cooler, reducing the chances of overheating. Intercoolers also enable your engine to produce more horsepower because of the denser air charge being delivered to the engine's combustion chamber.

Don't assume, however, that you can simply bolt an intercooler on to your supercharged engine and expect power gains with no other changes to the system. Intercoolers do create some internal drag causing a slight reduction in boost, and can also cause the engine to run lean (knock) due to the denser air charge. These problems are easily corrected and should not cause concern, however they cannot be ignored. Boost pressure can be brought back up (actually you'll probably want to run substantially more boost than you did with a non-intercooled application) using a smaller supercharger pulley. The smaller supercharger pulley will spin the supercharger faster and increase its output. Make sure your supercharger is designed to handle these higher boost levels. Correcting the air/fuel ratio to compensate for the denser air charge can be done with larger fuel injectors, recalibrated FMU, larger fuel pump, adjusting the mass air meter, etc.

Obviously, intercoolers only work with supercharged or turbocharged vehicles where there is a substantial difference in temperature between the air entering the engine and the cooling medium (the intercooler). Because superchargers heat up the air significantly as they compress it, it is possible for there to be a very large temperature difference between the intercooler (ambient air temperature - 80F degrees or so) and the compressed air (200F - 350F degrees). Superchargers with higher boost will create a hotter discharge, so as you increase your boost, the effects of the intercooler become more and more noticable. In general we would not recommend intercoolers on supercharged engines with less than 8-9psi of boost, as the benefits will not be substantial. Essentially, run an intercooler when only when you running peak boost (i.e. any more boost would cause detonation) for the octane of fuel you use. Intercoolers work well in both warm and cool climates and work exceptionally well on marine applications because of the easy access to cold water.

So while intercoolers work well on higher output superchargers, they are not recommended for lower boost level kits, like an average 6psi street kit. If you're looking for exceptional performance from your engine, consider adding an intercooler to your engine, or consider purchasing a supercharger kit that comes with an intercooler. Most ATI ProCharger systems include intercoolers and still remain very reasonably priced. Paxton has also recently introduced several intercoolers to fit their more popular supercharger systems, while Vortech already includes intercoolers with several kits. Good luck with your intercooling endeavors, wherever they may take you!