What Is an Intercooler?

What Is an Intercooler?

Last Updated December 8, 2020 | Alison Smith

Intercoolers are heat exchangers used with forced induction systems, like turbochargers and superchargers. Their purpose is to cool the compressed air before it's sent to the engine. This results in better engine performance.

What Does an Intercooler Do?

Intercoolers take the compressed air from a turbo or supercharger and extract the heat to reduce the temperature. Forced induction systems compress the air, which increases the temperature. As the temperature rises, the air density decreases.

An intercooler works with the supercharger or turbo to send cooler, denser, more oxygen-rich air to the engine. This helps increase engine efficiency and prevent engine knock for better reliability.

Intercooler GIF showing how hot compressed air from a turbo is cooled by the intercooler so cool compressed air is sent into the intake manifold

Types of Intercoolers

There are two main types of intercoolers: air-to-air and air-to-water. Intercoolers are typically mounted in between the engine and the supercharger or turbo. Some intercoolers mount on the top or side of the engine. Placing an intercooler in these locations isn’t as effective since they can suffer from heat soak. These setups need more air routing methods to get the air into the intercooler.

Intercoolers have a core, piping, and end tanks. The intercooler design affects the cooling and airflow properties. More fins allow for better heat transfer, but a higher fin density can restrict airflow. The size is also important. Bigger isn’t always better, as an intercooler that is too large can cause boost lag.

Air-to-Air Intercoolers

Air-to-air intercooler in front of white background

Air-to-air intercoolers usually mount in the front of the engine bay for easy access to the outside air. They're more common than air-to-water intercoolers as they’re cheaper, weigh less, and have a simpler design.

A drawback of air-to-air intercoolers is the longer intake length. Since they’re mounted in the front of the engine bay, more tubing is required to reach the engine. This can result in wider variations in temperature. They also rely on the air generated by the vehicle being in motion, so heat soak can be an issue when the car’s at a stop.

When it comes to the design of the core, there are two main options: tube-and-fin and bar-and-plate.

Tube-and-Fin Intercoolers

Tube-and-fin intercoolers use a network of tubes with cooling fins to reduce heat. They transfer heat as air passes through the system, sending cooler and more dense air to the engine. They’re cheaper than bar-and-plate styles and have less of a pressure drop for better airflow. However, heat soak can be an issue and may cause overheating, which will reduce power.

The tube-and-fin design is common on stock intercoolers. Performance intercoolers usually have a bar-and-plate style.

Bar-and-Plate Intercoolers

Bar-and-plate intercoolers are stronger and heavier than tube-and-fin intercoolers. They’re also more expensive but provide greater heat transfer and cooling. The air passes through a series of plates and bars that act as a heat sink. They can handle more abuse compared to the tube-and-fin intercooler. Bar-and-plate intercoolers offer better performance at a higher cost. They’re better in stop-and-go traffic as they can hold a cool charge better.

Air-to-Water Intercoolers

Underhood image of an air-to-water intercooler installed

Air-to-water intercoolers are also known as air-to-liquid intercoolers or charge air coolers. They use water or coolant to transfer heat from the air as it passes through the system. Heat is extracted from the compressed air by the liquid that’s pumped through the intercooler. The cooled air goes to the engine while the heated water goes through another cooling cycle. Typically through a separate radiator.

Also referred to as heat exchangers, air-to-water intercoolers are smaller than air-to-air intercoolers. This makes them great for smaller engine bays where space or intake length may be an issue. Compared to air, water is more efficient and can handle a large temperature range.

Air-to-water intercoolers are more complex, but also more effective. They’re heavier and cost more as they have coolant and transfer lines, a pump, and a radiator. Where air-to-air intercoolers go in the front, air-to-water systems have more options. They can be mounted in other places in the engine bay as long as the radiator can get proper airflow or has a thermo fan.

Intercoolers vs Radiators

Both intercoolers and radiators are different forms of heat exchangers. While almost every car has a radiator, not all have an intercooler. Intercoolers are only used in cars with a forced induction system. Radiators use fluid or coolant to transfer heat to the air to keep the engine cool. Not all intercoolers operate this way. So while they serve a similar function, they’re not used in the same capacity.

Does a Turbo or Supercharger Need an Intercooler?

Intercoolers aren’t required with a forced induction system, but they are recommended. An intercooler won’t add any horsepower, but the added engine efficiency can contribute to better performance. Some supercharger and turbocharger kits even come with an intercooler included.

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Sources: Turbosmart, Engineering Explained, Super Street, On All Cylinders | Image Credit: Creative Commons

What Is an Intercooler?

Superchargers and turbos compress air, which increases the heat and reduces the density. Intercoolers are sometimes used with these forced induction systems to keep the air cool and dense for better engine efficiency. The two main kinds of intercoolers are air-to-air and air-to-water.