TurboCharger System Facts

One of the most over looked items in a turbocharger system is the intercooler/ aftercooler setup. Without it, high boost levels and great performance wouldn't exist.

A turbocharger utilizes expanding exhaust gases to spin an exhaust turbine wheel, which in turn spins an impeller on the intake side of the turbo. The downside to turbochargers is that the excessive heat is transferred through the housing and impeller, which heats up the air being pushed into the engine. The use of an intercooler/aftercooler helps chill the air so the engine can use it more effectively. Essentially, intercoolers are just heat exchangers designed to cool off boosted air from a turbo or blower.

Excessive heat is unfavorable for making horsepower; cooler air is denser and carries more oxygen. It's my opinion that we've seen an over­whelming success of turbochargers (and centrifu­gal blowers, too) in the drag-racing world largely because the intercooler systems are capable of chilling the air to ridiculously low temperatures. Cooler air allows the engine to accept greater boost levels, higher static compression, and advanced ignition timing without the threat of pre-ignition from hot cylinder temperatures. Racers can run whatever size turbos they want, but if they can't keep the inlet air temps at a reasonable level, the engine won't produce maximum horsepower numbers.

There are two categories of forced-induction heat exchangers-air-to-air and air-to-liquid. In most hot-rod circles, an intercooler refers to an air-to-air intercooler, while an aftercooler is an air-to-liquid. Technically speaking, an intercooler should be referred to as an aftercooler because it cools the air after it's discharged from the blower or turbo. The original description of intercooler stated that a cooler was mounted between two turbochargers. The intercooler chilled the air exiting the first turbo before it entered the second one in a sequential twin-turbo system, hence the moniker "inter." Over the years, the term "intercooler" has been widely accepted to mean an air-to-air heat exchanger nestled between the turbocharger(s) and the throttle body/carburetor. It should really be called an "aftercooler," but it's too late to change now.

Usually, liquid-to-air heat exchangers rely on water and ice (or another form of coolant) to drop the temperature of the incoming air. This type of heat exchanger has picked up the nickname "aftercooler." Vortech Superchargers is largely responsible for applying the aftercooler name in the Mustang market. In the mid-'90s, it debuted an upper intake manifold that doubled as an aftercooler. It wasn't new technology by any means, but it definitely was the first of its kind in the Mustang and street-legal drag-racing markets.

The Vortech piece was virtually a bolt-on item for small-block Ford engines. At the time, most turbo racers used air-to-air intercoolers, but the Vortech unit made it easy to step up to a more efficient system. It started a craze, which led to larger blowers and turbochargers as rac­ers found a better way to cool down the hot air emitted from their boost makers. As soon as the blowers and turbos got bigger, so did the liquid-to-air aftercoolers to cool down the big boost. Before anyone knew it, they were being mounted behind dashboards and eventually took resi­dence in the passenger seat and backseat when the physical dimensions became monstrous.

Around 2000, we saw a big changeover from the air-to-air intercooler to the more efficient liquid-to-air intercoolers. Using ice and water is far more effective in chilling boost in that type of application, but it is more cumbersome. If it wasn't for intercoolers, it's safe to say that turbochargers wouldn't be as effective and probably wouldn't have prospered so well in the Mustang hobby.
An intercooler, whether air or water-cooled, is fairly basic and carries the same concept as a radiator. Air or water pass through a series of fins that cool down the air on the other side of the wall. Mounting them becomes tricky in most street applications, though. The size and shape don't offer too many logical and clean locating positions. Race cars, by far, have the easiest solution with a passenger-seat or back-seat mounting position. If the cooler is mounted inside the cabin, a series of tubes enter and exit through the firewall.

Some street enthusiasts custom build an intercooler mounting location that sits behind the lower front valance. It's ideal for air-to-air cool­ers because of the air rushing over it at speed. Air-to-liquid coolers can be mounted in a variety of locations and are usually custom units, but some blower companies make universal kits that can be used on turbochargers. Ford has even used aftercoolers on many of its specialty cars like the '03-'04 Cobra, the Gen 2 Lightning, and the Shelby GT500. Enthusiasts who convert to a turbo with those cars usually build a custom bonnet to cover the lower manifold (which is an aftercooler setup). This helps simplify turbo conversions with easier charge-pipe routing and overall ease of installation/fabrication.

Whether you use an intercooler or after-cooler, chilling the boost will help produce more power and quicker times.