Here some write-up about Intercooler.
What is an intercooler?
An intercooler is typically a box shaped object that allows hot air to enter, and cools the air down as it reaches the exit of the intercooler.
How does an intercooler work?
An intercooler works off the basic principle of heat transfer. The tubing of the intercooler allows airflow to pass through the "core" of the intercooler. On the outside of these tubes there is fins. The fins in a nut shell provide greater amount of area that the heat is able to be passed through. The greater surface area effectively lowers the airflow temperature passing through the tubes of the intercooler core.
I see tons of different intercoolers on the market, what are the differences?
There is two types of intercooler cores produced, tube & fin and bar & plate. Here is a list of advantages/disadvantages to each:
Tube and Fin
Benefits:
Low cost
Low weight
Disadvantages:
Lower efficiency compared to bar and plate
Can be poor quality dependant on supplier
A little more awkward to modify core size
Some brands are plastic sealed at ends and have limits on welding techniques
Bar and Plate
Benefits:
35% greater heat sink capability (meaning you effectively COULD have a SMALLER intercooler when compared to the tube and fin)
Generally known as the "better product"
Easy to modify size and re-weld
Disadvantages:
Weight
Cost
Some limitation in sizes
I understand the different types, now what actual differences are there between different brands?
The true differences in the heat transfer qualities intercoolers have is the internal fins inside the tubing of the core. There is essentially fins on the inside and outside of the cores, allowing for even greater heat transfer to occur. The internal fins are a restriction to overall flow ability of the intercooler, which account for a greater pressure drop between the inlet and outlet of the intercooler core.
What brands are tube and fin or bar and plate?
PWR is a tube and fin construction with internal fins, Apexi is a tube and fin construction with internal fins, HKS is a tube and fin without internal fins and Greddy uses tube and fin, and on some intercooler models use internal fins.
Spearco is the largest bar and plate manufactuer. There is other bar and plate manf. on the market, but they are pretty small companies.
So what you are saying is Spearco is the best since its bar and plate?
Spearco is a great intercooler, and has been used on many successful racing cars. While bar and plate is the best design, tube and fin with internal fin technology can be as good, or better at transferring heat. PWR is my personal favorite choice for intercoolers. The price, construction and efficiency is greater than the similar spearco core size.
Now that I understand what are some good brands, how do I choose what size intercooler for my power goals?
Intercooler sizing is heavily dependant upon the intercoolers construction, material quality, type and efficiency. The size of the intercooler is also heavily dependant upon how efficient your compressor is within the boost range you going to operate it, how much psi you are going to be pushing through the intercooler and how much exposure to the ambient air the core will receive.
Just like the fins of the intercooler giving more surface area for the intercooler to act as a heat sink, or pull heat away, the larger intercooler will have a greater surface area than a smaller core. The price to pay for a larger intercooler core is increased pressure drop between the inlet and outlet of the intercooler, as well as a marginally increase in lag. You should select the intercooler core to reflect the amount of boost you'll be running through the core, and the efficiency range of the compressor you are using to turbocharge the engine. Falling outside the efficiency range will create a hotter incoming airflow to the intercooler core. The hotter the air, the more surface area you need to cool down the airflow.
Another aspect of intercooler selection should be the dimensioning of the core size. Choose a core size that will allow for the greatest possible heat transfer to occur, i.e get as much of the core exposed as possible. Ideally you want the intercooler as thick as possible, keeping the length to a minimum. Unfortunately in the real world you only have so much cool airflow that can make contact with the intercooler surface, having a super thick intercooler (greater than 3") does not work well. An increase in length of the intercooler should be desired instead of increasing the thickness, allowing the maximum possible airflow to reach the core.
Here is rough guideline of whp levels the PWR cores are rated for:
18x6x3: 350whp
20x8x3: 400whp
22x8x3: 450whp
24x8x3: 500whp
24x11x3: >600whp