Updated: Oct 16, 2021
An engine is already scorching hot; with the addition of turbochargers and superchargers, an engine gets even hotter due to increased air intake temperatures.
However, too much heat in an engine may produce engine knock, either detonation or pre-ignition, none of which are desirable and can rapidly damage an engine.
Luckily, a pretty simple device known as an intercooler can help reduce this air intake heat and cool down the engine.
This is especially important in tuned vehicles, which is why you may want to upgrade your intercooler.
Table of Contents:
What Is an Intercooler?
Intercoolers are mechanical devices that are used to cool a gas after it has been compressed.
Sometimes an intercooler is also known as a charge air cooler or charge cooler, among other similar phrases.
Compressing a gas, such as air, increases the energy of the gas, which in turn raises its temperature.
An intercooler is usually in the form of a heat exchanger, which exchanges the heat from the intake air to the atmosphere.
You can find a wide range of uses for intercoolers in several products, including air compressors and air conditioners, refrigeration systems, gas turbines, and of course, automotive engines.
Generally speaking, they are utilised to enhance volumetric efficiency in a forced induction (turbocharged or supercharged) internal combustion engine.
This enhanced volumetric efficiency increases the engine's power potential and is achieved by raising the density of the intake air.
How Does an Intercooler Work?
An intercooler is a type of heat exchanger, which means it exchanges heat from one thing to another.
In this case, it exchanges the heat from the compressed intake air to the atmosphere air.
It does this by flowing the charged intake air through an enclosed tube with lots of small metal fins inside; this enclosed tube has many other small metal fins attached to it externally, which air from outside travel through.
These many metal fins transfer the heat away from the pressurised air into the atmosphere air, thus increasing its density and power potential.
Types of Intercooler
There are two main types of intercooler, air-to-air and liquid-to-air.
In terms of an air-to-air intercooler, there are also two main types known as bar and plate and tube and fin intercoolers.
There are also many variations of placement, construction and features of an intercooler, which I'll explain further down.
Click the above sections to skip to them or scroll down.
When someone mentions an intercooler, the air-to-air kind is the one that most people think of.
This type of intercooler is usually visible from the outside of the car, especially if it is front-mounted.
There's a reason its prominent placement; it requires high airflow.
The ability of this cooler to have an effect on intake air temperatures is dependent on airflow through it.
An air-to-air system is also very efficient; nevertheless, it depends on airflow (which is determined by vehicle speed) to produce the necessary cooling.
When there is minimal or no airflow at idle, these coolers may be susceptible to a process known as heat-soak.
Heat soak may be even more of a problem if an air-to-air intercooler is located inside an engine bay; it may even overheat at idle when engine bay temperatures begin to impact the intercooler's performance.
The air-to-air intercooler is the most common and usually the most feasible type; therefore, this article will be based on the air-to-air intercooler.
As the name suggests, the liquid-to-air cooler transfers heat from the air flowing through it by using the engines coolant.
The coolant and the air are in separate channels and do not directly touch one another.
Due to this type of intercoolers high efficiency and reliability, it has found its way into the engine compartments of a variety of OEM cars.
Heat is transferred between the air and the coolant via small metal fins.
A low-temperature thermostat is usually used to control fluid temperatures in a system like this.
When it comes to very powerful vehicles that generate a lot of heat, liquid-to-air systems are usually the better option when compared to air-to-air intercoolers.
This heat exchanger system is more complex than a typical air-to-air intercooler as it necessitates the installation of coolant lines and fittings and the installation of a coolant pump and possibly an additional radiator.
For the vast majority of cars, a more conventional air-to-air cooler is sufficient for both street and also track usage.
Bar & Plate
Bar and plate intercoolers feature more rectangular air galleries than other types of intercoolers, which allows a greater amount of compressed air to flow through the intercooler at one time.
However, airflow flowing through these galleries is more difficult since they are less aerodynamic.
They are less efficient than a tube and fin intercooler, but they are often more durable and can tolerate greater air pressure than a tube and fin intercooler
They are also heavier and tend to have a lower pressure drop.
Tube & Fin
Air galleries in tube and fin style intercoolers are curved on the edges.
This is due to the curved borders, which reduces their total air capacity.
When ambient air is sent through the tube and fin intercooler to cool the compressed air, the tube and fin intercooler produces less resistance than other types of intercoolers.
Tube and fin designs are often more efficient and lighter than traditional designs, although they are not as robust, which could be a concern for some use cases.
As a result, they are unable to withstand as much boost pressure as bar and plate style intercoolers.
In addition, the pressure loss in tube and fin intercoolers is greater.
The fins on an intercooler are a critical component in its construction, since they may mean the difference between a highly efficient cooler and a terrible intercooler.
The number of fins increases the amount of heat exchange, as we have already said; nevertheless, this comes at the cost of airflow and restriction.
Changing the height and pitch of the fins generate variations in the total surface area of the fins, which will help to increase density and therefore cooling ability.
FPI (fins per inch) may vary considerably both inside and externally.
When it comes to internal and exterior fins, the pitch and height are usually the same. The main variation is the kind of fin used.
Cooling fins, both internal and exterior fins, are available in a variety of forms.
When it comes to automotive intercoolers, there are usually two styles of fins.
In general, intercoolers have an interior fin with an offset design and an exterior fin with a louvred straight design.
This design creates turbulence inside the cooler, which improves heat transfer, while also allowing ambient airflow to travel freely through the exterior fins of the cooler's core for better cooling.
As you can see, the offset type fin seems to have much greater surface area for air interaction than the traditional form fin.
The offset type of fin seems to have much greater surface area for air interaction than the traditional straight fin.
This configuration will cause air to split many times as it travels through the core, thus increasing the amount of heat exchange that may be accomplished.
While this will result in improved heat transmission and reduced intake air temperature, it will also result in greater pressure loss, which you should consider.
Most high-quality aftermarket intercoolers will use an offset fin style to maximise intake air cooling.
Straight style fins are usually cheaper to produce and are used more often in OEM vehicles.
Which Type of Intercooler Is Best?
The most significant disadvantage of buying a liquid system is the expense, which may be as much as two to three times more than the cost of an air-to-air configuration, depending on the components utilised in the setup.
The majority of users will be able to obtain the necessary intake air cooling performance from an air-to-air configuration, which is much cheaper and usually easier to install and setup.
As for the variations of air-to-air intercoolers, the most effective for most use cases (assuming it will be front-mounted) seems to be a bar and plate type with a high-density offset-fin style.
Though, if the budget is lower then a bar and plate with a straight-fin style works as well.
Placement of an Intercooler
There are three main places to mount an intercooler, as listed below.
The top-mount intercooler is a kind of heat exchanger that is quite popular for stock heat exchangers.
Subaru's and Mini's use this type of intercooler placement quite often.
The name refers to the position of the intercooler, which sits on top of the engine's cylinder head.
It is supplied with airflow via a hood scoop or some kind of ducting from the front grille for this type of cooler.
Placing the intercooler in the engine compartment offers a number of advantages.
Firstly, this cooler is in a secure position where it will not be damaged by road debris.
Suppose you are driving your turbocharged car down a race course when an uninvited stone finds its way into your front-mounted cooler and causes it to burst open.
The second advantage is a shortened path for pressurised air to travel through, reducing the turbo lag and improving throttle response.
However, there are certain disadvantages to using a top-mounted intercooler system.
Heat soak is likely to be the most significant issue.
Considering that the intercooler is housed inside the engine compartment, it will almost likely be subjected to the heat produced by your engine and exhaust system.
When using a top-mounted intercooler at idle, intake temperatures tend to increase significantly, which may have a detrimental impact on power output.
The installation of a bigger intercooler in place of the original one would undoubtedly assist to minimise the occurrence of heat-soak, but the only way to completely remove it would be to relocate the cooler to a different position.
A side-mounted intercooler is becoming more rare nowadays, although it was formerly standard equipment on a number of cars.
This cooler might be regarded a kind of middle ground between the top mount and front mount, and it is usually only available as a factory standard option.
On one of the side intake openings of the bumper, a cooler is mounted to this system and is located toward the front of the car.
As opposed to the conventional bumper design, which blocks airflow via its central section, the side-mounted intercooler draws air in from the side of the bumper.
Because of space limitations, the size of this intercooler is often very restricted, which has an impact on the amount of power and airflow it can handle.
Additionally, pipes must be longer in order to transport air outside the engine compartment and back in again.
For these reasons, it is not usually used as an aftermarket option and is mostly replaced by front-mount intercoolers.
A front-mount intercooler is a modification that not only lowers intake temperatures, but it also adds some visual appeal to the vehicle.
Seeing a big intercooler installed on the bumper of a vehicle is a simple way to recognise a fellow petrolhead enthusiast.
Regarding the usage of front-mount vs top-mount coolers in terms of boost lag and real power advantages, there have been many heated discussions.
In spite of the fact that a front-mount system would usually generate the lowest intake temperatures of any of the available choices, it will also create the greatest boost lag.
Depending on the power of your vehicle and your planned usage case, this limitation should be taken into consideration; nevertheless, for optimum intake air cooling, the front-mounted intercooler is the best option.
A disadvantage of a front-mount type of intercooler is it usually reduces airflow to the radiator and can therefore have a negative impact on coolant temperatures, though this is usually minimal.
Intercooler End Tanks
An end tank is what connects the core of an intercooler to the intake and boost hoses.
While end tanks may seem to be a minor consideration when compared to the size of your intercooler, it is vital to pick an intercooler with the right end tank design.
The kind of end tank you choose will have a significant impact on the reliability of your intercooler, as well as the airflow.
Your end tank must be efficient and allow air to travel through it with minimal restriction.
There are four main designs of end tanks, as listed below.
This list is in order of worst to best, plastic end tanks being the worst and cast being the best.
Plastic End Tank
Plastic is not the material of choice for a high-performance intercooler end tank.
While plastic end tanks are great for stock vehicles that produce low boost levels, they are not great when a vehicle is tuned, which could cause cause the end tank to crack, come apart or even explode from the air pressure.
Diesel vehicles are especially prone to these kind of problems.
When manufactured in large quantities, a plastic end tank is much less expensive and lighter than metal alternatives.
Automotive manufacturers are looking for every opportunity to decrease both the cost and the weight of their cars, which is why plastic end tanks are installed in nearly all stock vehicles.
Plastic will continue to deteriorate over time as a result of the continuous changes in temperature and pressure.
Normally, this manifests itself in the form of a fractured or broken end tank.
As well as causing total failure, crimp connections may also spread when subjected to continuous high boost, which can ultimately result in a boost leak.
A rubber gasket is included inside the crimp connection, and it is responsible for providing a seal between the aluminium core and the end tank.
Leaking connections, even if they are minor, may cause extra wear on your turbocharger and engine if they are not discovered.
Oil leakage from intercooler end tanks is typically the first sign of a problem.
However, there is one benefit from using a plastic end tank which is they usually have higher efficiency due to optimised air flow and ease of production.
Stamped End Tank
A middle ground between plastic and cast end tanks are stamped end tanks.
These one-piece designs have the advantage of being more cost-effective (especially for large-scale production) while also being more durable.
Typically welded to the intercooler core, these end tanks may be seen on some older turbocharged cars.
Intercoolers with stamped end tanks are capable of withstanding high boost pressures.
Stamped tanks are much stronger than the plastic equivalents.
However, they are not a common material of choice for OEM components.
Cut & Weld End Tank
A cut and weld end tank is better than the stamped end tank in durability but may not flow as well as its cast alternative.
It is possible to remove failure spots associated with plastic end tanks by fabricating them out of aluminium and welding them to the intercoolers core.
However, these end tanks are usually constructed from a variety of smaller metal components, which provides for a number of possible failure sites.
When working with such a design, precision welding, appropriate testing, and effective quality control procedures are required in order to prevent errors.
Generally speaking, a well-constructed cut and weld intercooler will offer excellent longevity and should be able to take almost any amount of boost.
Cast End Tank
A cast end tank is at the top of our list since it combines the greatest characteristics of durability and efficiency.
It is cast into a single piece of aluminium that is then welded to the intercooler's core
Failed crimp connections, cracks, boost leakage and reliability issues are usually all eliminated with a cast end tank.
This end tank design, in addition to providing a more durable structure, enables easy optimisation of airflow.
Intercooler engineers can use computational fluid dynamics (CFD) software to fully optimise and improve an intercoolers efficiency and effectiveness.
Manufacturers can even install air diverters in the interior of the end tank, further improving the cooling ability of the intercooler.
In summary, a cast aluminium end tank will be the best option from both a reliability and efficiency standpoint.
The opinion of surface finish on intercoolers in varied, some people like the look of bare metal and some prefer the look of a painted intercooler.
Aesthetics is a personal preference but does it make a difference to its effectiveness? No, the difference between a painted intercooler and a raw metal intercooler is almost non-existent.
It seems that no matter the type of surface finish, an intercooler will still work great.
Below I'll go into detail on each type of surface finish.
This list is in order of cost, wet painting being the cheapest and anodising being the most expensive.
Wet painting an intercooler is also an option if you want a finish that is fairly long-lasting and durable.
Painting is inexpensive but it will not be as durable as powder-coated intercoolers.
It is also a less time-consuming method that does not need the use of an electrical charge or a high-temperature oven during the curing process.
Overall, wet painting is a cheap and effective way to surface finish an intercooler.
When it comes to intercoolers, powder coating is the finish of choice for the vast majority of them.
Apart from being visually appealing, it also offers a very durable surface that is resistant to damage caused by road debris.
Powder coating is a process that involves applying an electric charge to a surface, spraying paint in the form of a dry substance, and baking the paint into the surface.
Anodising is a technique that is usually reserved for nonferrous metals such as aluminium and titanium.
Even though there are several different anodising processes, it usually includes pretreatment and cleaning in an alkaline detergent, an acid bath, the electrical anodising process, a colouring process, and finally a sealing process.
It is the most time-consuming and costly way to surface finish an intercooler.
Intercooler vs Radiator
The radiator and intercooler are two separate components with two separate jobs, below are some comparisons of their function.
The radiator cools the coolant, which becomes heated as a result of engine heat.
The intercooler is a device that is used to cool down compressed air from the turbo.
Engine radiators are liquid-to-air.
Intercoolers may be either air-to-air or liquid-to-air, but they're usually air-to-air.
The radiator dissipates the heat generated by your engine coolant, allowing the engine to operate at an optimal temperature.
In order to make the air entering the combustion chamber denser and colder, heat is removed from it by the intercooler after it exits the turbocharger.
They work on a similar principle as a heat exchanger but they have two fundamentally different jobs.
Benefits of a Bigger Intercooler
There are four major advantages of installing a bigger intercooler, as listed below.
Cooler & Denser Intake Air
As a result of installing a larger intercooler, you can have more intake air cooling.
This extra cooling will increase the density of the intake air, increasing the amount of oxygen for the same volume of air.
More oxygen means more combustion in the cylinder, meaning more power.
Reducing intake air temperature has a direct effect on power.
Less Risk of Engine Knock
Another major advantage of installing a bigger intercooler is that it reduces the risk of all types of engine knocking (not including rod knock though).
Reducing the risk of engine knock means you can run a more aggressive tune and higher boost pressures.
This reduced risk of knock is due to decreased intake and cylinder temperatures.
Installing a bigger intercooler is not the only way to prevent engine knocking, you can also install a water/methanol injection system along with various other ways.
Click here to see ways of preventing engine knock.
Reduced Heat Soak
Heat soak is where the entire intercoolers temperature increases, sometimes to a point where it cannot cool down the intake air temperature until it has cooled down itself.
This heat soak can happen after hard driving, such as on a track, or where the ambient temperature is hot, such as in hot weather.
Usually, driving calmly (not on boost) for a few minutes can bring back down the intake and intercooler temperature.
Installing a larger intercooler is a great way to prevent heat soak from happening.
There's also an inexpensive modification called an intercooler water sprayer which can also further reduce intake temperature.
Reducing heat soak can help you drive on boost for longer, increasing track times and power.
More Aggressive Aesthetics
If you're a modified car enthusiast then you know a tuned car when you see one.
Usually, the first signs of a tuned and modified car is a big intercooler showing through the bumper.
Most enthusiasts would say that a big intercooler showing through looks good, but it's personal preference.
Though, it usually makes a car look more aggressive.
Should You Get a Bigger Intercooler?
Modifying your car is a personal choice, but if you're after a better performing and more powerful car then getting a bigger intercooler should be on your modification list.
The optimal intercooler for most people would have the following features:
Bar and plate
Cast and flow-optimised end tanks
High-density internal fins and low-density external fins
Offset-style internal fins and straight louvered-style external fins
In summary, getting a bigger intercooler will provide much better intake air cooling, increase power and prevent engine knock.