[s-cars] RE: [200q20v] intercooler

Calvin & Diana Craig calvinlc at earthlink.net
Mon Dec 3 19:53:33 EST 2001

OK guys, here's what I can come up with.  The calculation below is accurate
for NA engines.  Depending on how highly tuned, camshaft profiles etc., the
engine is the VE can range from .85 to 1.05 or so....yes you can actually
have above 1.0 because of ram induction given a "high rise" manifold in the
old carburetor jargon.  At any rate, the VE is how well you fill the
cylinder with air (I know some of this is basic but...)  Assuming a near
vacuum in the cylinder when it is being filled (not manifold pressure but
internal to each cylinder) there is a VE of let's just say 0.9 for a
pressure differential of 14.7 psi.  If you take this and add on an extra
20psi of boost, your pressure differential has just gone up to roughly 2.4x
what it used to be.  Ignoring temp. increase inefficiencies and fringe
effects, I believe that the ratio of CFM required to fill this cylinder
should also go up by that same factor, so if we get 208 cfm NA, then it
should require about 499 cfm.  This also equates roughly with what I would
expect since a usual V-8 producing about 300 HP requires about a 600 cfm
carburetor to run correctly and not be out of carb at the upper end...kind
of a sanity check if you will.  That's my .02 cents.
--Calvin Craig
Parker, CO
'92 S4
'91 200 TQ
'89 200 TQW
'72 Formula Firebird

-----Original Message-----
From: Brian Link [mailto:brianl at starsys.com]
Sent: Monday, December 03, 2001 1:16 PM
To: 'mlp'; b.m.benz at prodigy.net; brett at cloud9.net
Cc: Scott Justusson; 200q20v at audifans.com; s-car-list at yahoogroups.com
Subject: [s-cars] RE: [200q20v] intercooler


Do you have any temperature data, Im looking for a rough shot at cooling
efficiency, the stock UrS4 can't be too much different from the 200 20v.
 Can it?

I calculate approx 208 cfm at 5300 rpm, lets suppose that is equal to
engine bhp of 230 that would be .9 cfm per bhp.  (?)

CFM = rpm * (Engine displacement ft^3 )/2  (?)

Im using a peak flow 19.7 lbs/min (.85 VE) as the mass flow rate.  I'm
using an inlet air temperature of 130F (wag).  Up here in CO.  I'm spinning
my k-24 at 140,000 at 20 psi????

-----Original Message-----
From:	mlp [SMTP:mlped at qwest.net]
Sent:	Monday, December 03, 2001 12:47 PM
To:	b.m.benz at prodigy.net; brianl at starsys.com; brett at cloud9.net
Cc:	Scott Justusson; 200q20v at audifans.com; audi20v at rennlist.org;
s-car-list at yahoogroups.com
Subject:	[200q20v] intercooler

Date: Sun, 02 Dec 2001 12:43:57 -0800
Bernie Benz <b.m.benz at prodigy.net> wrote:

>The 200-20V ICs have an effective core length of 15", the 5Ks are
>The open flow CSA I have measured as being 6.2 square inches,
>open flow CSA I have measured as being 6.2 square inches,
>twice that of 2" ID inlet piping @ 3.14 sq "

In the FWIW data pile, I believe (courtesy of Bob P.) the UrS4 IC
works and runs something like this:

Gross exterior Core dimensions:

- @ 9.25" Wide (this is a "cold" flow/ i.e.. cooling face dimension
- @ 11.0" Long "Hot" charge air flow dimension
- @ 3.75" Deep.
- CSA gross internal open face @ 13.5" square (see below.)
- IC's Inlet tube INSIDE diameter @ 54mm/2.1" = surface area (Pi*r^2)
= 3.3" sq.
- IC's Outlet Inside diameter @ 62mm/2.42" = surface area of @ 4.6"

The UrS4/6 IC's gross exterior dimensions manage to encompass within
its 9.25" "height" fifteen (15) rows of "pressurized"  charge air
flow, sandwiched between 16 rows of external air cooling fins.  The
charge air travels the 11" length of the cores height tube length.

Each charge air row contains two (2) internal tubes, measuring @1.5" x
.3" each for a total "CSA" if I'm using Bernie's term correctly, of
approximately 13.5 sq inches.

Each of the internal charge air tubes is filled with its own tiny
internal cooling fins (? turbulators), through which, in stock form
the K24 turbo at peak delivery is supposed to cram @ 227 bhp worth of

If I referencing the same 'measurement' Bernie, the UrS4's 13.5"
square inches of internal flow face vs. the 200TQ's 6.2" square seems
a significant difference.  Is the 200TQ's IC stuffed with internal
cooling fins as well?

If one were to use @1.6 cfm per bhp as a rough rule of thumb
bhp-to-cfm conversion figure, one is looking at stuffing something
like @ 360cfm of atmosphere through the IC at peak power? or do you
folks have a better figure for the required, or desired flow volume?

The IC inlet pipe (hotside charge from the turbo) is relatively
"smaller" i.e. I get @54mm or 2.1" of INSIDE diameter, vs. the IC's
outlet to the throttle body hose, which is @62mm or 2.42" in diameter.

On the other hand I notice the Outlet side has to make a fairly funky
bend, which it looks to me some one may have spent at least a little
time thinking about the short side radius of the turn on the outlet
side.  My guess is that the pinch that's molded into the end tank at
that point isn't just an accident, but was done for some reason of

> The two cores were combined by first swaging the inlet side
> of each core tube end opened, such that the outlet tubes of
> the first section slip into the inlet tubes of the second ....
> The mating tube plates were then welded together .....
> I have the swaging tool, if any one wants it.

Bernie, what's the "swaging" tool?


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