Cool tuning for cooling performance

Direct charge air cooling

In our “Introducing a product” series, we give you essential information, tips, and tricks about modern vehicle technologies and equipment in a compact, competent, and uncomplicated form.

We’ll start the year with the first of three parts. In each part, we’ll introduce a product that is now available in the MAHLE product range following our acquisition of Behr Hella Service. Today, we’ll talk about charge air coolers in general and specifically about the “direct” variant. We’ll explain which two types are available (air cooled/air and water cooled). Let’s go!

Higher performance, lower emissions

You’ll certainly be familiar with the general trend in the passenger car sector: vehicles need to deliver better performance, but at the same time they have to be more compact and lighter—and this is leading to a rise in the number of turbocharged engines. Turbocharging generally involves cooled charge air. The higher charge air density achieved in this way increases the output and efficiency of the engine.

However, it is not only the number of turbocharged engines that is increasing, but also—due to the required reductions in consumption and emissions—the demands on the charge air cooling capacity. These demands can be met by cooling the charge air using air and/or coolants. This makes it possible to reduce the NOx (nitrogen oxides) and HC (hydrocarbons) emissions, while increasing the effect of the exhaust gas aftertreatment.

Aside from improving the cooling capacity, the charge air cooling must take on an additional task: tempering the engine process air by regulating the charge air cooling. The tempering is made necessary by the steadily increasing demands on exhaust gas aftertreatment—the temperature of the charge air plays an important role here.

Charge air cooling at a glance:

  • Types: Air cooled and coolant cooled
  • Task: Increasing the performance of the engine by charging (more combustion air, higher oxygen content)
  • Properties:
  • Higher dynamic cooling capacity
  • Improved engine efficiency by increasing the charge air density
  • Lower combustion temperature, resulting in better emissions values
  • Fewer nitrogen oxides at –40°C to 160°C
  • Test pressure = 20 bar with a burst pressure of 50 bar

Exhaust gas turbocharging—the basis for modern, high-performance passenger car engines

How can you make performance even cooler?

You see, modern coolers have to do more and more, but at the same time the passenger car needs to become lighter and, if possible, smaller. There is therefore very little available space in the vehicle’s front end. Large-scale charge air coolers, which are installed in front of the coolant cooler and cooled with ambient air, are now rarely found in modern vehicles. Instead, charge air coolers with an integrated precooler (water cooler) are used.

Charge air precoolers—tuning for cooling capacity in a compact design

By using the charge air precooler, which is fed with coolant from the engine circuit, some of the charge air waste heat is shifted from the charge air cooler to the coolant cooler. Although additional charge air waste heat is produced as a result of the performance increase, this can be dissipated through the precooler. As a result, the concept of a block-shaped charge air cooler can be retained.

The charge air precooler, like the charge air cooler, is mounted in the front of the vehicle so that it is also cooled by the ambient air. Thanks to the charge air precooling, the performance of an existing concept can be significantly increased. The required overall installed size of a charge air precooler is 40% to 60% of a charge air cooler.

In the next part ...

... we’ll introduce you to the latest and most powerful variant: indirect charge air cooling. We’ll also show you how to detect damage to cooling systems quickly and where the causes might be found, and we’ll give you tips and tricks for repairs. So, come back and take another look!


We regularly provide technical tips relating to the powertrain, thermal management, and mechatronics in automobiles.


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