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JohnJL's Avatar
 
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How much is too much intercooler?

I'm building this car here and the time has come to build the intercooler. I have a massive amount of space under the tail. The pics below show the actual size model of what space I have to work with.

I have a theory that at some point the diminishing marginal temperature reduction is offset by the amount of aluminim needed to build the next size up...something vague about thermodynamic efficiencies and some law named after an Italian guy. Anyway, I'm sure an intercooler 24" by 20" by 7.5" deep is unnecessary. That's 61cm by 50 cm by 19 cm.

Can anyone add any theory, science or experience as to what is a proper size if I have those dimensions to work within? Here are a few pics of a box I constructed demonstrating the available space...

Motor is a 3.2 revving to 6500 with 16 lbs boost. Target 475 hp. Air/air intercooler.

Thanks






so thats what an intercooler's view of the world looks like..



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2007 911 Turbo - Not a toy
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Old 01-28-2009, 02:29 AM
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I believe Corky Bell has some dimensions on his website to determine IC needed. Maybe, it would answer your question.

But for now, bigger the better.
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Old 01-28-2009, 04:30 AM
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I'd maximize surface cooling area instead of volume, meaning cover as much of the tail inlet as possible.

I talked to the guys at Bell Intercoolers before I built my mine since I was worried about it being too big. They said if it's been more than a few weeks since I'd driven the car (it had been almost 2 years ), I wouldn't notice the increased lag due to the larger intercooler volume and I didn't.

Your climate should be considered too. It's very hot where I am, so I could use the excess capacity on the track.
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Old 01-28-2009, 05:25 AM
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There are good arguments to designing an intercooler with more or less thermal mass, depending on intended application. High thermal mass ICs are great for the occasional street blast, wherein the IC just "heat-sinks" the induction, then has plenty of time to recover. Vs a good track IC that is subjected to cycle after cycle of boost and must sacrifice some heat sinking effectiveness in favor of being able to cool off as much as possible in braking zones.
Thicker core and end tank metal = better heat sink, and vice/versa.
The other things to consider if you're making your own IC is pressure loss and volume. Pressure loss is usually directly inverse to thermal efficiency, and a higher efficiency IC may be better for street (less lag) whereas a larger IC may be better for the track.
Sweeeeet project, I can't wait to be building my own IC!
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Old 01-28-2009, 08:46 AM
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Can anyone talk in more detail on the disadvantages of a smaller frontal area with a thick core versus larger frontal area with shallow depth core? They both would have the same surface area of aluminum exposed to flow, just that the the air must pass thru either a thicker or thinner depth of cooler.
I don't know if I worder this clearly, but my B&B intercooler is thick and smaller surface area perpendicular to cooling air flow versus the 964 OEM cooler which is large surface area with thinner depth. Which makes a better overall cooler assuming they have equal volume?
Anyone have outlet pressure drop values for a B&B cooler running 0.8 bar inlet pressure from turbo? Looking for some idea on how much pressure drop to expect across this intercooler. Makes me wonder about the advantage of running the wastegate signal pressur e line after the intercooler to eliminate this loss.
Thanks,
Fred
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Old 01-28-2009, 10:04 AM
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Thanks guys. I did go back to the Bell books and site again last night.

This is a race-only application so heat-sink ability while idling isnt a concern, but weight up high, WOT flow and reduction of any "lag" due to unnecessary volume between the supercharger and the intake are concerns.

The tail "opening" is only 14" front-to-back so the intercooler will already exceed that area.

Bell says the first 1/4 depth of the intercooler does 3/4 of the work. So maybe maximise the width of 20", 4" depth and 16" length is the go? That leaves 4" on each end for tanks and baffles. If we mount it all the way up to the bottom of the tail we should be able to easily "seal" it so all the engine fan's air comes in through the intercooler. It will also leave room underneath it so we can mount a "pull" fan underneath the intercooler if that proves necessary.

Any help or suggestions?

BTW, I'm not doing the building, Paul is. I'm just doin the learnin' and the payin' of bills.
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Old 01-28-2009, 12:13 PM
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FYI, the bar and plate type intercooler like Bell's are heavy. My core is 25x12x4.5 and the whole intercooler weighs 30 pounds.

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Old 01-29-2009, 03:45 AM
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Quote:
Originally Posted by 125shifter View Post
FYI, the bar and plate type intercooler like Bell's are heavy. My core is 25x12x4.5 and the whole intercooler weighs 30 pounds.


Beautiful Fab Work, well done!
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Old 01-29-2009, 05:50 AM
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Bell does great work
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Old 01-29-2009, 10:06 AM
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I just did the cutting and fitting, some welders at work did the rest.

I did copy (somewhat) DonE's intercooler which was fabbed by Bell, and yes they do good work at a good price.

I had some things I wanted to do inside, that I didn't think Bell would want to bother with.

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Old 01-29-2009, 10:24 AM
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