Have an intercooler question?

Is there a nagging technical issue causing you problems? We have your answer. We’ve assembled a collection of the more common intercooler related questions covering a wide variety of topics. However, if you don’t find your question answered below, feel free to contact us and we will be glad to answer any questions you may have on intercooler theory, design and production.

What is the purpose and/or advantage of an intercooler?

The purpose of the intercooler is to remove the heat in the air charge that the turbo/supercharger puts into the charge when compressing it. There are two advantages: Reducing the heat in the air charge increases the charge density (more molecules of air per cubic foot), thus increasing the potential for making more power. Reducing the heat decreases the tendency of the combustion process to knock (detonation).

How does the intercooler affect the power output of the engine?

Power is dependent on the density of the air charge. By decreasing the temperature the intercooler increases air charge density, therefore, the power is increased. Typically, the magnitude of the increase will be between 10 and 20% for the average (street) boost pressures.

Is some intercooling better than no intercooling?

No. It depends on the design of the intercooler, and there are two factors involved; efficiency (how much heat is removed) and the flow restriction (lost pressure) created by the presence of the intercooler. Regardless of the efficiency, if too much pressure is lost, then the intercooler is either useless or can actually decrease performance.

Are there varying styles of intercoolers?

Yes, two basic styles: Air-to-Water, whereby the Charge-Air is cooled by Water, and Air-to-Air, whereby the Charge-Air is cooled by (ambient) Air.

How can an air-to-air intercooler be more efficient than a water based intercooler?

There is an overwhelming quantity of ambient air available to cool an air-to-air core relative to the charge air thru the inside of the intercooler (The iced down water intercooler is the only exception to this argument.). At just 60 mph, with a 300 bhp engine at full tilt, the ambient air available to cool the intercooler is about ten times the amount of charge air needed to make the 300 hp. Whereas the water intercooler largely stores the heat in the water until off throttle allows a reverse exchange. Some heat is expelled from a front water cooler, but the temperature difference between the water and ambient air is not large enough to drive out much heat. Another way to view the situation is that ultimately the heat removed from the air charge must go into the atmosphere regardless of whether it’s from an air intercooler or a water based intercooler. The problem with the water intercooler is that the heat has more barriers to cross to reach the atmosphere than the air intercooler. Like it or not, each barrier represents a resistance to the transfer of heat. The net result; more barriers, less heat transfer.

What are the relative merits of an air or water-cooled intercooler and which would suit my purposes best?

This depends on the circumstances. These circumstances are; street use, drag racing, or endurance racing (more than two minutes).

Street use: The air-to-air intercooler will prove superior in efficiency when sized properly.

Drag racing: The short spurt of power allows the iced water to cool the charge air to below ambient temperature.

Endurance racing: The air-to-air intercooler is clearly superior due to the shorter route of getting the heat out of the air charge and into the atmosphere. Endurance racing would preclude the use of ice water, thus negating the singular advantage of the water intercooler. Further, the air-to-air intercooler is (virtually, see comments below) maintenance free.

What factors are considered in configuring an intercooler?

Use of the vehicle: note the answers above.

Space: When insufficient space exists for an air intercooler of adequate internal flow area, then a water based unit is the better choice. A water intercooler usually reverses the flow paths through the core and puts the charge thru the big face, thus its flow area can be quite large even in a small overall package.

Type of core: There is very little distinction between core types with respect to efficiency. Charge air flow: This is the factor that determines the intercooler size.

Does one style core cool better than another?

No, almost no difference. With three decades of testing intercooler’s, we have found no appreciable difference between any core style or manufacturer. Keep in mind, that the merit of a core is it’s efficiency versus its internal drag characteristics. When sized for a tolerable flow loss, virtually all cores will produce essentially the same efficiency results. Perhaps a core with slightly less flow area per linear inch, or one with longer tubes, will need perhaps 5% more tubes to equal the best of intercooler’s with regard to flow loss and efficiency. Not a very important difference.

What are the variations in core construction used in intercoolers?

The variations are in the style of manufacture of the core material. A “Bar and Plate”-Style Core is made by brazing up a layered structure of flat plates separated by small rectangular spacers. A “Tube and Flange”-Style Core is created by extending a series of tubes through a header flange and brazing the assembly together. For heavy duty applications, pressure spikes up to 250 psig and rugged environments, ”Solid Extruded Tube”-Style Cores are available.

What are the differences between short tubes and long tubes?

The longer the tube the greater the pressure loss accompanied by a slight increase in efficiency.

Does the length of the tube affect efficiency?

Very little. The most heat comes out of the tube where the temperature difference between the inside and the outside is the greatest. That exists in the first couple inches of the tube. The last inch of the tube, wherein the charge temperature is rapidly approaching the cooling media temperature, will transfer very little heat, thus being of minor use.

What factors affect efficiency of an Air-to-Air Intercooler?

Frontal area: This is a rapidly decreasing function. If the proper core size is used, then doubling it will definitely not double the efficiency. More likely, doubling the core would raise the efficiency about 5% and cost twice the necessary amount and add substantially to the weight.

Plate area: Plate Area (the sum of the Core-Plate Area which is exposed to the Atmosphere) is directly proportional to the frontal area and the thickness. Thickness, however, is a double-edged sword. With the greater thickness, the plate area increases but less ambient air can penetrate the thicker core to offer cooling.

Ambient air quantity: It is very important to insure that air coming in the snout of the car will actuallygo through the intercooler.

Are there any improvements that can be made to the system for improved efficiency?

Yes, several small factors influence the efficiency. A proper duct is probably the single most beneficial thing that can be done to an existing intercooler. Positioning in the main stream of ambient air is crucial. By comparison, a taped up intercooler with no ambient air flow will offer only about 20% efficiency.

What ranges of efficiency can be expected from an intercooler?

A typical air-to-air intercooler for a street application achieves between 60% and 70% efficiency, an excellent/optimum design for road racing can approach close to 90% efficiency, but requires an adequate “budget!”

Typically, a liquid-to-air intercooler achieves higher efficiencies than an air-to-air intercooler, starting at 75% efficiency and reaching peaks of 95% efficiency. Another advantage is the optional use of ice as a coolant, which is the only way to reduce the charge-air temperature below the ambient air temperature.

How does one measure the efficiency of the intercooler?

The efficiency is defined as the ratio of the temperature removed from the air charge by the intercooler relative to how much temperature is put into the charge by the turbo/supercharger.

For example: If the turbo/supercharger puts 150 degrees F into the charge when compressing the air, and the intercooler removes 110 of those degrees, then the efficiency is:
Eff = 110 / 150 = .733, or 73.3%

What factors affect the pressure or flow loss?

The internal flow area is the major controlling factor. Tube length is the second biggest consideration, as a tube twice as long as another will have nearly twice the drag at the same air velocity. Tube entry and turbulator density play small roles and can be considered insignificant. When configuring the orientation of the core in a given space, always position the core to offer the shortest length tube and the most number of tubes. Clearly, this optimizes the internal flow area.

What ranges of pressure loss can be expected? And what is acceptable?

For good solid performance, the pressure loss across the intercooler ought to be kept to less than 1.0 to 1.5 psi. If any pressure in excess of 4 psi is measured, then the intercooler is not suited for the job and certainly harming the performance.

Does one core style offer less restriction than another?

There are a few fine points that mean little. Essentially, they are all the same if the flow area is the major design consideration.

What is flow loss thru an intercooler?

Flow loss is what is measured in the pressure loss and is the restriction presented to the smooth, easy air flow through the system. Essentially, the drag. It is measured by a pressure difference between the air charge entering the intercooler to that exiting the intercooler. This flow loss is due to the aerodynamic drag offered by the shape, the net area of the tubes, the length of the tubes, and the density and style of the turbulators.

How/why is the flow loss significant?

The net result is the production of power. It is hugely important because the power required to drive the air thru the system must come from somewhere. Depending on whether the system is turbocharged or supercharged, will determine how much power is lost from the restriction.

Are there other factors of flow loss, in the intercooler assembly, rather than just the core?

Yes, entry into the intercooler inlet tank and the smoothness of the exit tank. The adjoining tube assemblies, their length, size and bend configurations are all part of the flow loss total.

If the boost is raised is it necessary to increase an otherwise proper intercooler?

Very seldom. While the loss through the intercooler is proportional to the flow (CFM) squared, unlikely the change will be of a magnitude that requires a bigger intercooler. If dramatic changes in flow are created, say 50%, then the flow loss would increase by 1.5 squared, or 2.25, and that would prove excessive thus strongly suggesting a larger intercooler.

Can an intercooler fail? If so, what are the failure modes?

Water-to-Air intercooler Systems have many obvious failure modes; Pumps, leaks, hoses, reservoirs, corrosion and even a lack of maintenance, all can contribute to a failure. The Air-to-Air intercooler Systems are hard pressed to fail if properly built for the job; running into solid objects, like other vehicles, is probably the only significant cause of failure.

Is there a boost pressure limit for intercoolers?

Intercooler’s can fail from pressure if not specifically designed to operate at that objective pressure. The failure mode is definitely not like a bomb going off, rather a failure is manifest in cracked seams, and is induced by repeatedly flexing the material of the end tanks. A panel of the cap, if large, subjected to high pressures, and in-adequately stiff, will flex in-and-out, or “oil can,” until the edges of the panel fatigue and the seams begin to crack. (Pressures up to 15 psig are usually safe for all designs)

What is the importance of a leak in an intercooler?

With the water intercooler, a leak in the main cooler core could induce a significant problem into the engine. External leaks are just annoying, but not likely to be harmful. The air unit must have a very large leak before it can cause any problem whatsoever. If pressurized and placed under water, an air intercooler will need to “billow” bubbles before it causes any noticeable problem. A dozen small trickles of bubbles would be entirely meaningless to performance.

How can an intercooler be protected from corrosion?

The water unit will need water passage protection offered by standard anti-freeze.
The air intercooler only needs the outside protected from corrosion. Powder coating is perhaps the most durable/cost-effective solution to corrosion. The charge paths of either style intercooler will be protected by the oily vapors from the engine breather that are pumped through the system.

Can an intercooler be painted?

Certainly. One might find a small loss of efficiency if the core is painted, but likely this would be less of a difference than the repeatability of measurement. By all means, paint the end tanks, but preference suggests the core remain exposed.

Can an intercooler be repaired?

Repair depends on where the problem is and how badly it is damaged. Its much the same as “can a fender be repaired?” In most cases, an able fabricator, a band saw and a heliarc welder can do wonders.

Is there a maintenance regimen for an intercooler?

The water based intercooler will need periodic attention to the water level. Further, it needs anti-freeze for cold weather use, corrosion and pump lubrication. An occasional leak inspection would be advised.The air intercooler needs de-(smashed)bugging when washing the vehicle. Tube hoses and clamps need periodic checks. If the air intercooler develops minor leaks, this is usually of no consequence.

Perhaps every 10 to 15K miles, the internals of the intercooler element ought to be washed out with a solvent to remove the accumulated oil residue and grime.

What is a life span of an intercooler?

With minor maintenance, essentially unlimited. Except for the water intercooler’s pump, of course.

Does an intercooler carry a warranty?

Yes. All Bell Intercoolers Cores and Assemblies are guaranteed for one year against workmanship failures.