ish

iTrader: (7)

i am still sticking to my belief which appears to be in agreeance with meilers.

everything that i know about thermodynamics, heat transfer, physics, and fluid mechanics from school leads me to believe that computer fans will obstuct air a lot more than it could help.

wheelerjb

you could always take a block of dry ice and fuse it to the intercooler(by spraying water on it). A guy that did the texas mile shootout did that and ran the car just over 150mph with the block on his intercooler. he is running stage 4 and his EGTs never went over 1250 IIRC. he was also running 18-20 psi as well, maybe a little more. so either his tune was way off, or the dry ice really lowered the temps. NASIOC is down now, but i have seen the video that shows his speed, temps, and boost. plus I talked to him about it because i didn't believe his EGTs and boost.

ride5000

meilers,

i will prove you wrong.

with data, not a bunch of pontificating.
later,
ken

Lachlan

iTrader: (2)

I can't add much, but I'll say this:
The velocity of the air going through your IC is proportional to the translational momentum (and thus energy) it has. When the air spins a fan, some of that translational momentum turns into angular momentum coupled with the fan. Thus energy moves from the air to the fan, less energy in the air means it moves across the IC slower. How much slower? I don't know if it's slow enough to make a difference.

Cliff's Notes: The fan will slow the air, but it may or may not be enough to make a difference.

Oh, and I think I see a flaw in the baloon theory. When you're blowing up a balloon, the velocity of the air is very slow, and the change in pressure is slow, which means you are always very close to equilibrium. Air going through an intercooler at highway speeds never reaches equilibrium, so it will never "spread itself out" (it may try, but won't succeed) across the IC.

meilers

No, that's not the case; it doesn't have anything to do with eqilibrium or velocity, but how compressible air is. Certainly the air at the back of the scoop will have a slightly higher PSI than the air just entering the scoop, but the high-PSI air will always flow towards an area of lower pressure, period. In this case, air under the intercooler will always have lower pressure than air entering above the intercooler; if you are traveling at sufficient speed to pressurize the air in the scoop, the air will be drawn down through (or pushed through -- pushing and pulling are the same thing, to a physicist) at an equal pressure on all surfaces. This situation happens regardless of air velocity, until the air velocity is so great that the air is skipping the scoop entirely (which supposedly can happen at over 130 MPH). Despite the claims of those selling splitters, it is literally impossible to have "dead spots" where no air is reaching the intercooler, unless you are moving too slowly to create that pressure differential between the top and bottom of the intercooler. There is definitely a time-delay between when the air gets pressurized and when it reaches equilibirium, so your instincts in this situation are correct, but the net result is the same.

If you mentally replace the air with water (the two behave with remarkable similarity) it is easier to visualize. If you pour water into a bucket with holes in the bottom, you are always going to get equalized pressure coing out of all of the holes, regardless of how fast or slow the water is enterting -- unless the flow of water is so slow that the water drains out before it reaches all of the holes. If there is sufficient water to cover all of the holes, you will get an equal stream out of each regardless of pressure or how the water is entering the bucket.

There may indeed be some conditions of vortex or nonlinear flow under the hoodscoop itself, which is probably what the splitter designs are supposed to prevent, but as long as the high-to-low pressure gradient exists, the air will still flow through the IC. The real problem, and the origin of this thread, is how to deal with those situations where you are not moving fast enough to actually create that pressure differential. Fans on top of the IC, as you note, will disturb the airflow already created by our knowledgeable Subaru engineers; fans below the IC don't have a pressure seal with the hood scoop area and don't have much room to be installed; thus why the STI comes with a water-spray system from the factory, and not fans.

My personal vote is for the block of dry ice on the IC, but this clearly isn't practical for around-town driving

ride5000

silver arrow, don't waste your time on non-believers: they know too much, and you don't have any clue what you're talking about.

Mister 2

iTrader: (14)

You state that "the high-PSI air will always flow towards an area of lower pressure" and then assume that the lower pressure is on TOP of the intercooler thus leading to "an equal pressure on all surfaces". This is not the case. In case you've forgotten there is a lower pressure region under the intercooler as well. Without a splitter there will be higher pressure (and flow) thru the back half of the intercooler vice the front.

Here's a picture of the bug distribution over an intercooler as an example .

Br1t1shguy

just put some sprayers in, they work 10x better than ****ty little comp fans ever will, they dont obstruct it when it counts, and it's alot simpler

EQ Tuning