I feel like I should say something here. There's a possibility for us to grow as a community. When I first saw these $100 intercoolers I felt that it was a great thing. For the longest time it felt like name-brand companies were fixing prices for a lot of performance items. I understand the need to bring in R&D money and all, but I recall $900 Spearco intercoolers as the norm, and that's just madness.
These cheap eBay intercoolers seemed to be of the correct design, material, and quality for use in serious cars. After having first-hand experience with them I can now say they not only
seem to have these qualities, but they do.
I'm going to link to an article with stuff you need to know about intercoolers so we can have a decent discussion. Don't skip this link. It is mandatory reading for everyone. Once you get to the "Doing Things Differently" section you can stop (unless you want to keep reading).
Fusion Intercooler
Combine this notion of an air-to-air intercooler as a heat sink first, and a radiator second along with everything Corky Bell has to say about intercoolers and we can now start to understand what make a name-brand intercooler better than the eBay units (because there must be something behind the gains, if there are any).
I'll summarize what Corky Bell says here:
Given the same sized core, it's all in the end tank design and placement.
You want the end tanks on the ends of the core that will give you
lots of short passages for the air to travel through instead of a few long passages.
If you can, put the outlets of the ends tanks in the middle.
If not, try to have the outlets on opposite passages (top and bottom instead of both on top)
If you can, try to have
curved end tanks, not
square ones.
If you can, have
baffles inside large end tanks to help direct air flow. (I've never seen a company employ this.)
Aside from end tank design, there is a balance to be made with the amount of fins to place inside, and outside the air flow.
Too many fins inside the air passages and you loose air flow, too few fins and you won't cool the air much.
Too many fins outside and the outside air won't flow through the intercooler (and it will dissipate less heat), too few fins and the outside air will flow through the intercooler without dissipating much heat either.
Another area of design is the height between air passages and the height of the air passages. More distance between air passages increases fin surface area and thus quickens the cooling of the intercooler by outside air, yet lowers the number of (or height of the) air passages you can have, decreasing charge flow through the intercooler.
Next up is the design of the fins themselves. There is a "louvered" fin design which is basically a staggered fin which results in better cooling but less flow than traditional fins.
Now, here is the fin design/density of a typical eBay intercooler:
Source: Ebay
Here is the fin design/density of a very high end (
FCP) core:
Source:
FCP vs. Spearco core
There's also the plate ends to take into account. For most cores (including the high end) this is
the design.
This would be an improvement.
If you've made it this far, you might be asking "Well Ben, how would you build your ideal intercooler?" and the question is tough to answer. What type of driving do you do? Is it daily driving? Spirited daily driving? Some track time thrown in? Autocross? Endurance racing?
There are things we care about in our intercoolers. What is the temperature difference across it? What is the pressure drop across it? How long does it take to saturate? And at what temperature does it saturate?
You may not care about time to saturation or saturation temp in a drag race, but the endurance racer sure does.
If I were to set out and build my own ideal intercooler I'd want to take advantage of all of the known techniques for making it great. There's a lot of trade-offs though, and I'd have to pick a goal for my driving first. If I were trying to market an intercooler I'd have to make assumptions and I'd probably end up somewhere in the middle.
If the eBay intercoolers really are losing to the name-brand units at very high HP outputs, it's due to the pressure drop. The question is then, is the pressure drop due to the designer (copier?) making a compromise with fin design, or is it just poor design overall (tiny leaks, less-than-ideal transitions, etc.)? This is assuming there is a significant difference of which I'm still not convinced.
I feel I'm rambling, and I'm late for an engagement so I'll leave you with this for now:
ARE Cooling (Aluminium Radiators & Engineering P/L)
If you haven't had enough, read that link or at least look over the pics. He even has his own take on eBay (Chinese) intercoolers.