FMIC -- need clarification
 

can some one give me a techinical idea of why everyone says


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this is the good style of FMIC


while

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this is bad?




so....why is that so? They look different. Also, how much difference is there really?

are you talking about the difference between bar and plate the top one you shown... and tube and fin the lower one you showed?

yeah

LOL, I thought the top one was a tube and fin type and the bottom one the bar and plate. Obviously the bar and plate type won't get as damaged from road debris, but other than that I'm not too sure about the difference either.

Vertical flow cores typically have lower pressure drop due to the fact that the height of the core is typically short (versus length).
Horizontal flow cores have more pressure drop due to less and longer tubes, but that does not automatically mean it's "worse".

The bottom line is the IC is there to cool the intake charge.
As long as it does it's job, everything else is secondary.
If there's too much presssure drop, just jack the boost higher. :D


-Ted

With everything else being equal, the bottom one will have more pressure drop, which is a fancy way to say that it absorbs some of the boost from the turbo. In reality, of course, things are not equal. The better manufacturers use different construction methods for each of the above intercooler configurations in order to help compensate for the pressure drop issue. Also, an intercooler with the top type of configuration generally does not fit in the RX-7 as well as the bottom configuration. I think the bottom line is to get a well-made intercooler that fits in the car, and not worry so much about some of the other issues. I think your only other main concern should be the thickness and density issues that affect how easily air can flow through the core, especially on a street car. Rule of thumb is 3 to 3.5" max, but this varies.

The trouble is that ends up heating the air more so you make less power, doesn't really solve the problem of an inefficient intercooler.

The upper and lower will both have the same frontal area, heat transfer area and efficiency, but assuming the tanks are on the top and bottom of the upper example, it will have greater internal flow due to the greater number of tubes and therefore lower pressure loss.

Thats generally true, but sometimes the pressure drop actually moves the turbo up to a more efficient range. It still requires more turbo rpm, which means more lag, but I don't think drag racers would mind all that much, lol.

Example: The red line shows the turbo needing to run at a higher pressure ratio to create the same boost in the manifold with an intercooler that has an increased pressure drop over the green line. Note that the red line actually passes through higher efficiency islands on the map, altough the turbo needs to be able to spin faster to do it.

https://www.rx7club.com/attachment.p...chmentid=84450

This is generally true for a given intercooler core size. However, once again, real life shows us that this is not necessarily the issue. Most people are sizing intercoolers by the space available in the car, not according to a given intercooler core size. Therefore, there are situations where the longer intercooler will have more internal volume when fit into a given space in the car.

Example of what is usually the case... trying to cram an intercooler core AND end tanks into a small space:

https://www.rx7club.com/attachment.p...chmentid=84452

Which one looks better now? :)

Anyway, these types of situations are what RETed was referencing. You can't always go by the Corky Bell numbers. ;)

EDIT: Double Post

That's the trouble, real life could never have anything to do with pure physical theory :P

This site here is the one i was lookinng at. the 349 dollar one. I need a IC because the TII i bought lacks the top mount. I would like to avoid the pressure loss if possible but the price is in my range. I cant spend 1000 dollars on an IC. Hell the car didnt even cost that much.

the other option i was exploring seeing i have to have custom pipes for this shindig. Why not go v-mount? i can use a 24" x 10" core with HKS vertical end tanks TIGed on. The pipes would be shorter which would be good. Also, i would keep it from the crappy ass northern weather. I can run an e-fan on it if i really need to as well.

Theory holds true for the most part. The main problem comes in when people try to apply ONE theory when several factors exist in reality. ;)

Physical external dimensions are only part of the story. There are many other factors in choosing an intercooler:
https://www.rx7club.com/attachment.p...chmentid=84452

The cheap intercoolers are usually not very efficient. However, they are better than nothing, and I totally understand the budget limitations.

Do you mean v-mount or horizontal mount? Either way, less bends and less piping is better, but just make sure air has good way to pass through the intercooler.

Like the bitches that mention Ideal Gas Law when talking about turbos? :D


-Ted

Exactly. It does hold true for the compressor, but the turbine, engine, and rest of the system are another story.

Hey, Hugh MacInnes is all about PV = nRT, so lay off, man. :hippie: