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Originally Posted by Hot Compact & Imports magazine
The tube and fin core design is the most economical to produce and therefore more affordable to consumers. The tube and fin intercooler is also relatively light in comparison to the bar and plate design (Like Kevin said), affording users a slight weight reduction. When the charge air enters the end tank, it travels through tubes in which the heat is transferred via fins where cooler ambient air passes over the tubes. This further removes heat from the air before exiting the opposite end tank en route to the engine. All in all, the tube and fin intercooler is perfect for the tuners building their first custom turbo systems on limited budgets. The disadvantages to the tube and fin intercooler is that its effective efficiency is lower when compared to a similar sized bar and plate intercooler.
Bar and plate intercooler cores function identically to the tube and fin core, with the exception that charge air travels through rectangular shaped passages that have more surface area, thus improving cooling of the air charge. The advantage to using this type of intercooler is that because the bar and plate core design affords up to 35% larger surface area for cooling, a physically smaller intercooler can be used and still retain the cooling characteristics (efficiency) of a larger tube and fin design. This is important for a builder who has a vehicle with a small opening in the front of it or where there are immovable obstructions present. There is a downside to this design, too, as it is generally more expensive due to the extent of fabrication that is involved in its construction. The bar and plate intercooler is also heavier due to the larger surface area and denser fin design. Simply put, it generally contains more material, thus the heavier weight.
The subject of tight space leads us to the third type of intercooler, the air to liquid or air to water, as it is commonly called. While the function of the air to water intercooler is the same as the air to air intercooler, its design and application differ greatly, as does its cost. The air to water intercooler is primarily used where space is at a premium and where plumbing intercooler piping to the front of the vehicle isn't practical. An example of this would be a mid engine vehicle such as the Acura NSX. Running intercooler pipes from the engine in the rear of the vehicle all the way to the front increases turbo lag, dampens throttle response and would be far more expensive. By using an air to water intercooler, all of these problems can be alleviated.
To better understand how this intercooler works, picture an air to air intercooler that's encased in sheetmetal. How does a design like that cool the charge air? There's more to this design than passing air over its cooling surfaces, as a liquid (such as water) is pumped through a fitting on the casing at one end and exits though a fitting on the other. Water passes over the core that has a denser fin design when compared to an air to air intercooler, since water is being forced throught it. As the water passes through the core, heat from the charge air within is removed. This effect is amplified by passing the heated water through a heat exchanger, located in direct flow of ambient air. This is a continuous process that results in the efficiency of the intercooler, which can approach or exceed 90% in many applications. This, of course, results in higher power levels and a greatly reduced chance of detonation.
The high efficency of the air to water intercooler allows its phyiscal size to be much smaller than even the bar and plate intercooler, which is a definite plus to owners of cramped engine compartments. If you wish to go one step further, you can place the intercooler in such a way that ambient air will pass over it as well, adding to the cooling effect. While this setup sounds great on paper, it's not without drawbacks. The problem with this setup is that it is not very practical for most street applications, as the ancillaries - such as waterpump, cooling tank/reservoir and lines - consume considerable space. Plus, the water and/or ice must be changed once it warms up or melts. For this reason alone, you mainly see air to liquid intercoolers used on race-only vehicles.
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