All About Intercoolers

There's no denying that supercharging and turbocharging engines is becoming more and more popular every day. Substantial increases in horsepower and torque, along with stock-like driveability make these power adders very appealing to a great many enthusiasts. In order to take these power gains to the next level, an intercooler must be employed, and we're going to tell you why you might need one, and what is available for your muscle Mustang or fast Ford.

The term intercooler actually dates back to the beginning of air-charge-cooling technology when piston-driven aircraft used multiple superchargers to boost power output. Air-charge coolers were installed between these superchargers (hence the inter part of the name) to reduce the air-charge temperature. Technically speaking, most of the current air-charge-cooling designs should be called aftercoolers since they chill the charge after the compressor, but the market has been slow to adopt the more accurate description. At this point, the term intercooler is used much like Kleenex or Coke, in that they have come to represent the type of product rather than a brand or exact product. For the duration of this article, we'll refer to intercoolers and aftercoolers simply as charge coolers.

In order to understand air charge cooling, or the concept of cooling the air that enters the engine, you must first realize that superchargers and turbochargers both pressurize the intake side of the engine. When you add more air and fuel, the result is usually increased power and torque. Compressing air, however, has the drawback of heating the air charge going into the engine. Heated enough, the hot air can cause detonation, among other serious issues.

To combat the increase in air temperature, a charge cooler (intercooler/aftercooler) is employed. By forcing the compressed, and subsequently heated, air intake charge through an intercooler, the emperature is reduced, as is the air pressure from the restriction posed by the intercooler. When both of these events occur, the result is a cooler and more dense air charge. The dense air charge, when combined with the appropriate amount of extra fuel, produces more horsepower and torque. The cool, dense charge also allows for more ignition timing to be run, which also adds to the increased power output.

Now that we've established the reasoning behind using a charger cooler, it's time to talk about cooling methods. Currently, there are two particular types of charge cooling methods that are used in the automotive industry. The first, and most common, is the air-to-air charge cooler. In this setup, air is passed through a cooler core, which is usually placed at the front of the car in the direct path of oncoming air. The air passes over the fins of the core, which pulls the heat from the air charge within the core. Some manufacturers use a top-mounted cooler, such as with the Mustang SVO, but for vehicles with larger engines, there usually isn't enough space to fit them above the engine.

The air-to-liquid charge cooler transfers the intake charge heat to an intermediate fluid, usually water or a common automotive coolant, which is passed through its own heat exchanger that is air cooled. Such systems have been used in all of Ford's most recent supercharged applications, starting in 1999 with the SVT Lightning and continuing with the SVT Terminator Cobra and Shelby GT500.

"The air-to-water setup is very efficient," says Ford Racing Performance Part's Jesse Kershaw. "It's more complex and difficult to add after the fact, but when we started from scratch, it made it easy-especially with a V-engine-because the core fits in the valley."