How Intercoolers Work
An intercooler is a heat exchanger used to cool the compressed air charge from the turbocharger. Air at ambient pressure and temperature is drawn in by the turbocharger, compressed, and the high pressure air charge is forced through the intercooler before reaching the intake manifold. Because increasing the pressure of air via the turbocharger 1) proportionally increases the temperature of the air (high pressure = higher temperature) and 2) cooler air is denser (lower temperature = higher density), intercooling is used to improve performance and efficiency. At the molecular level, a denser air charge contains more oxygen molecules per unit of volume, therefore increasing the performance potential of each combustion event.
Intercoolers, sometimes referred to as charge-air-coolers (CAC), are found on most, but not all turbocharged diesel engines. There are two types of intercooling:
• Air-to-air intercoolers use ambient airflow to cool the intake air charge in much the same fashion that a radiator is used to cool engine coolant.
• Air-to-water intercoolers use engine coolant to cool the intake air charge.
Water-to-air intercoolers are favorable in applications with spacial constraints, as they can be placed nearly anywhere in the engine compartment whereas air-to-air intercoolers must be placed in a location with adequate airflow (in front of the radiator, for example, is a common mounting location).
| Engine | Intercooler Type |
| 5.9L Cummins 12v | No intercooler 1989 - 1990, 1991+ air-to-air intercooler |
| 5.9L Cummins ISB (24v) | Air-to-air intercooler |
| 6.7L Cummins ISB | Air-to-air intercooler |
| 6.6L Duramax (all generations) | Air-to-air intercooler |
| 7.3L IDI (factory turbocharged models) | No intercooler |
| 7.3L Power Stroke | No intercooler 1994 - 1998, 1999+ air-to-air intercooler |
| 6.0L Power Stroke | Air-to-air intercooler |
| 6.4L Power Stroke | Air-to-air intercooler |
| 6.7L Power Stroke | Air-to-water intercooler (charge air cooler) |
Factory intercoolers are manufactured economically and perform well, however in many instances there are significantly more efficient units available designed for maximum performance and cooling. In addition, factory intercoolers may not withstand higher boost pressures experienced with aftermarket turbo setups. As a byproduct of cooler intake air temperatures, exhaust gas temperatures are typically experienced with upgraded intercoolers or after converting a non-intercooled application. Aftermarket intercoolers are available for most Cummins, Duramax, and Power Stroke engines. Performance gains will vary by application and additional modifications, although you can expect a minimum of 20 horsepower and up to 200° F lower EGT.