Packing more air and fuel into an engine’s cylinders has long been known to be an important part of the recipe for making more horsepower. For a naturally aspirated engine, mods like cold air intakes, large bore throttle bodies or carburetors, and free flowing intake manifolds help make it happen. But while these performance parts reduce restriction, cylinder filling is still limited to what can be drawn in by engine vacuum and atmospheric pressure.
Turbochargers and superchargers have long been used on diesel engines but they have become prevalent on gasoline engines because they can produce the power of a much larger naturally aspirated engine while delivering better fuel mileage and emitting fewer pollutants. That’s why turbochargers and superchargers have become so popular. These devices compress the intake air charge to increase the mass of air or air/fuel mixture in the cylinders.
However, compressing the intake charge presents problems. As we know from basic physics, compressing a gas raises its temperature, and in the case of a turbocharger, the intake charger is also in close proximity to the hot exhaust inside the turbocharger. Hot intake air contains less oxygen than a cool air intake charge, and it can also create unwanted effects like detonation. This why most modern forced induction vehicles cool the air intake charge with an intercooler between the turbocharger or supercharger and the intake manifold. The cooler air contains more oxygen so more fuel can be burned, increasing power.
There are air-to-air and air-to-water intercoolers. Air-to-air intercoolers transfer the heat from the air intake charge to the ambient air flowing through the core, and are commonly mounted where they are exposed to airflow at the front of the vehicle or flowing through an opening in the hood. Air-to-water intercoolers transfer heat to water flowing through the core and the system includes a pump, reservoir, and heat exchanger. If your turbocharged or supercharged vehicle doesn’t have an intercooler you need one, but even if your vehicle is so equipped from the factory you can do better with an aftermarket intercooler.