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Intercoolers 101

Intercooler FAQs

What is intercooler heat soak? Heat soak is when the intercooler can't dissipate the heat that it absorbs from the turbo fast enough. When an intercooler can't cool the charge air by removing the heat from it, it loses its effectiveness. This explains why turbo cars tend to run slower or have slightly less power when the weather is warm.

What is the purpose of an Intercooler? An intercooler's primary function is to cool the charge air after it has been heated due to boosting and the heat that is produced by the turbo before sending the air into the engine. As the air is cooled, it becomes denser, and denser air makes for better combustion (more power). Additionally, the denser, cooler air helps reduce the chances of knock.

FMIC, TMIC, SMIC - what do they mean? (Front Mounted Intercooler, Top Mounted Intercooler, Side Mounted Intercooler) terms which refer to the placement of the charge air cooler in the engine bay and in reference to the engine. Typically FMICs provide the best cooling capability, as they are located in front of the radiator for optimum airflow. SMICs and TMICs are commonly found on factory-turbo'd cars. TMICs are more prone to heatsoak as they are placed over the engine directly in the path of the rising heat and very close to the hood. However, when a TMIC is used in conjunction with a hood scoop, they can provide adequate cooling.

Will an intercooler help make more horsepower? Yes, although it is only indirectly responsible for helping make more power. Since the intercooler increases the charge air density, an intercooled engine will typically make more power than a non-intercooled engine with the same setup by allowing more air to be crammed into each cylinder.

What is the difference between an air-to-air intercooler and a water-to-air (liquid-to-air) intercooler? An Air-to-Air intercooler uses ambient air flowing over the fins to cool the charge air, while an Air-to-Water intercooler uses coolant (water) with a system similar to that of a radiator's cooling system. Traditionally, air-to-air intercoolers are used for street applications because of their lower cost and reduced complexity, while air-to-water intercoolers are used in race and packaging-constrained applications.

How do I select the proper intercooler core size? A major limiting factor in choosing an intercooler size is space constraints within the engine bay. If there is not enough room for an intercooler with adequate flow, then often a water-to-air intercooler is used instead to maximize the cooling capability of the surface area of the core. You want to make sure that the intercooler you choose is large enough to effectively handle the air. Too small of a core, and you will restrict the potential of the turbo by not allowing the charge air to be cooled adequately.

What is the best placement of my intercooler? The best place for your intercooler is directly in the path of the inflow of ambient air. Traditionally this has been right in front of the radiator in the front of the car, hence the term Front Mount Intercooler.

Will a FMIC block flow to my radiator? No. Since the intercooler allows air to pass through it, airflow to the radiator will not be blocked. However, using an intercooler core that is too thick and does not allow air to pass through it quickly or completely and airflow to the radiator can be restricted which can lead to potential overheating problems.

What is intercooler effectiveness and how do I measure it? Effectiveness is defined as the ratio of how many degrees of temperature that were removed from the charge air by the intercooler to the original temperature that is put into the charge air by the turbo.


If the turbo compresses the charge air to a temperature of 140 F, but after passing through the intercooler the air is 115 cooler (resulting in a 25 F charge air temperature), the efficiency would be: Effectiveness: 115/140 = 0.82 or 82% efficiency

Typically, air-to-air intercoolers for normal street applications range between 60% and 70% efficiency. Often, liquid-to-air intercoolers have effectiveness ratings from 75% to 95%. One common method of improving the cooling of the charge air dramatically in an air-to-water intercooler is the inclusion of ice as a coolant.

What exactly is 'pressure drop/loss' / 'flow loss' and how are they measured? Pressure loss, or pressure drop, refers to the change in pressure when comparing the air entering the intercooler with the exiting air. This change is mostly affected by the internal flow area of the intercooler. Flow loss, however, is measured not just with pressure loss but with how much restriction to airflow exists. Maximum performance can be obtained if the pressure loss is kept below 1.0 to 1.5 psi. Anything in excess of these numbers, especially higher than 3.8 psi, and the intercooler is not properly fitted for the application which results in hindered performance and dramatically decreased functionality of the intercooler system itself.

I want to turn up my boost, is a larger intercooler necessary? Usually, it is not necessary to upgrade the intercooler when raising boost levels. The pressure drop contributed by the intercooler is proportional to it's flow (CFM) squared. This relationship shows that it is highly unlikely the change resulting in loss from higher boost levels will require a larger intercooler. If there is a significant change however, such as 40% or 50%, then a larger intercooler may be necessary.

Is there a maximum amount of boost I can run on my intercooler? While it is possible that an intercooler can fail from boost levels being too high, it is a very rare scenario. However, if not properly designed to handle high boost, cracking along seams and of the endtanks can occur.

How significant is a leak in my intercooler? For an air-to-air intercooler, a leak, as long as it is not a significantly large one, will not hinder performance at all. However, if an air-to-water intercooler develops a leak in the main core, it could lead to other more significant problems with the engine itself. Be sure to fix these problems as soon as they occur to prevent other damage.

I want my car to remain a sleeper/stealth. Can I paint or anodize my intercooler so it is not easily visible? Yes! It is not uncommon at all for an intercooler and endtanks to be anodized black to keep attention away from the car and help it maintain a sleeper appearance. A very light coat of paint on the core and endtanks is also another option, usually much cheaper and easier than anodizing, with a negligible performance loss.

Is there any maintenance required for my intercooler? Are there any special things to do to keep it working longer? In a water-to-air intercooler, check the water level often as this is crucial for the intercooler to operate properly. In cold weather, just like a car, it will need antifreeze in order to function effectively and properly. With an air-to-air intercooler, there really is no maintenance that needs to be done other than just the routine checking of hoses and clamps to make sure everything is tight. Additionally, the intercooler fins may be picked-out or de-smashed to ensure maximum cooling. Every 20,000 miles or so it is recommended that the intercooler core be inspected, and if necessary, flushed/washed out to remove any accumulated oil or buildup.

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