[200q20v] intercooler

Bernie Benz b.m.benz at prodigy.net
Mon Dec 3 16:31:53 EST 2001

Michael, Thanks for the very interesting info on the UrS4 IC.

Apparently, the UrS4 IC is a more modified version of, but is in the same
design family as the 5K/200 IC core, in these respects:

1.  The hot side tubes have been increased in height from 0.2" to 0.3",
5K/200 and S4 respectively.  The other tube dimensions and internal fin
count remaining the same.

2.  The S4 core uses 15 double tube rows of these larger (taller profile)
tubes, whereas the 5K/200 cores use 13 double tube rows of the smaller
(shorter profile) tubes.

3.  Each IC uses a different core length, 13.5", 15" and 11" for the 5K,
200, and S4 respectively.

4.  Further calcs indicate that the cold side tube spacing has been reduced
from about .33" to .30" for the 5K/200 and S4 respectively, thus increasing
S4 cooling air flow resistance with resultant reduced charge cooling.

Changes 1, 2, and 3 cumulatively reduce S4 IC pressure drop, but also reduce
charge cooling under both steady state and trancient, heat sinking
conditions, relative to the 5K/200 core in a single pass configuration.

Michael, apparently your hot side CSA calculation was a gross estimate,
whereas mine is net of full radiused tube corners and internal fins.  If so,
on an apples to apples comparisome basis, your S4 CSA of 13.5 sq" might need
to be reduced by 8 or 10%, but still is a significant, 100% flow area
increase over the 5K/200 core!

Let's speculate on what Audi design has done in this ICed turbo system
evolution and why.

Obviously, over this 3 generation evolution, they have been moving in the
direction of drasticly increased IC flow capacity and reduced pressure loss
across the IC. (Larger and more tubes of shorter length.)  This evolution
has sacrificed forced induction aftercooling, thus is at the expense higher
and higher charge temperatures, i.e. smaller and smaller temperature drop
across the IC.

First, remember that our cars are not designed as race cars or Pikes Peak
performers.  IMO, They are designing cars for short burst performance,
relying primarily on the transient, heat sinking capabilities of the forced
induction system, rather than on the steady state capabilities of a good
intercooler design.  This stratigy requires that excessive charge
temperature be controled by the ECU in turbo bypass to reduce charge

A quick pop is all you get!


> From: "mlp" <mlped at qwest.net>
> Date: Mon, 3 Dec 2001 11:46:43 -0700
> To: b.m.benz at prodigy.net, brianl at starsys.com, brett at cloud9.net
> Cc: "Scott Justusson" <QSHIPQ at aol.com>, 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
> 13.5",
> ....
>> 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
> looks,
> 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"
> square.
> 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
> air.
> 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
> flow.
>> 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?
The swaging tool is a hammer driven, milled aluminum punch designed to
raduis the protuding inlet end of each tube for reduced entry air
turbulance, or to accept the outlet tube of the upstream core such that flow
is smooth from tube to tube.
> Michael

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