[200q20v] intercoolers

[Brett Dikeman]

At 6:23 AM -0500 12/4/01, QSHIPQ at aol.com wrote:

>Mike make be simplistic (ask Hap), but he's right on in terms of design and
>execution.  If you look at the "big dog" IC designs, you will see that short
>and more, beats long an less (ok insert jokes here;).  Bernie, for more on
>this, you can go to a variety of books, Try page 59 and 60 in Corky Bell's
>book for starters. Longer tubes = greater pressure loss across the IC = bad.
>
><snip>
>
>Frontal area is key, the more the better, the shorter the cores, better
>still.


Yep.  What I remember is that:

>---------------
   ||||||||||||||
   ______________>

is better than

>|--------------|
  |--------------|
  |--------------|>

...because overall, flow resistance is lower(lower pressure drop),
air velocity is lower in each tube, etc.  One of the many cases where
parallelism is a Good Thing.  I seem to remember Bell saying that if
you ever wanted to make an IC bigger, get a core with more tubes,
don't make all the tubes longer.  Think about it...which flows more?
Two garden hoses in series, or two running in parallel?

Case and point, the double-pass Audi intercooler is basically a
folded version of the second IC "diagram" up there; its two very thin
cores making what is effectively a very narrow long core*.  The
single-pass IC probably isn't the same dimensions, but its -about-
the same for Shadetree Mechanic purposes.  It's better because the
same number of tubes(roughly) are used all together in parallel, not
doubled up.

*There's also no funky problems with redirecting the air's velocity
180 degrees in a rather small, small space(which causes -additional-
flow resistance!)

   Tada, this is why the double-pass IC sucks compared to the
single-pass.  The 'ol 5kCST used to seem to really suffer from the
lousy IC.  The 200q20v seems to suffer on about the same level, but
it is handling almost exactly 14psi more boost from a -smaller- turbo
and slightly higher air "consumption" too(20v head vs 10v head,
better IM manifold too, slightly, yes?)

So, you say, why doesn't Audi do diagram #1?  Well, look at the crude
dimensions there in the picture.  See all the wasted space vertically
because of the end tanks?  Tada!  The stock IC is practically
smooshed into place(ask anyone that has tried to get the #$!%@ thing
out)  and seems to make great use of the space available.  Scott and
I were discussing larger ICs once, and he said "sure, no problem."
The word "cut" was mentioned and I immediately lost interest :-)

Also, it would seem to me from a Shadetree Thermodynamics perspective
that a core balanced towards longer tubes would be better designed
for lower flow rates of cooling air.

Want to drastically increase your IC's heat transfer?  Spray it with
a mist of water.  It doesn't have so much do to with water having a
high thermal mass, but what it does when it evaporates; the phase
change conveniently transfers -boatloads- of heat off whatever the
water was on.  Spraying your IC with alcohol would actually be
slightly better, but would probably make everyone in the car dizzy
every time you mashed the gas...and there's that whole flammable part.

Brett
PS: Listmaster Brett(200q20v list of course) says PLAY NICE.  A few
of the recent messages have been rather inflammatory.  Put some
better ICs on the keyboards, please.  Next nasty message gets a
Strike One(Strike three and yeeeeeeer outtahere!)  Oh, and it would
be nice to not open my email every few hours and see page after page
of messages on the same topic.  Some of this should be
debating/argued in private among the concerned individuals.  Go off
and have the conversation in a corner of the room, so to speak, not
over the restaurant PA system, eh?
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