If the turbocharger can be described
as the heart of the system, then the intercooler
must surely be the "lungs"!
APS has designed and manufactured a custom configured,
vertical flow high efficiency intercooler utilizing
custom designed light weight cast aluminium end
tanks. Extremely high flow rates and massive charge
air temperature reduction - a level of performance
that other manufacturers can only aspire to achieve.
With a huge 540mm x 250mm x 150mm (21.25"
x 10" x 6") drag race specification
bar and plate core, at 675 kW (900 hp) flywheel,
the pressure drop is less than 1 psi. At the same
turbocharger flow conditions, under full engine
load the intercooler outlet temperature is less
than 15°C (60°F) higher than ambient,
at any vehicle speed over 100 kph (60 mph). Truly
outstanding results at such a huge horsepower
level. So just like the APS turbochargers and
twin cold air intakes, the APS intercooler system
has massive additional headroom available for
even higher power levels.
Vertical flow inside the APS intercooler is by
far the optimum configuration given the space
considerations that must be accounted for in the
front of the vehicle. This solves the huge air
flow restriction problems that horizontal flow
cores experience particularly at high power levels.
The horizontal flow configuration
shown above forces the charge air to flow through
very few internal intercooler passages. In addition,
each internal passage is very long, causing further
restriction to charge air flow - resulting in
a high pressure drop.
The vertical flow configuration
as specified by APS spreads the charge air flow
evenly over a far greater number of internal passages
and results in significantly less restriction.
The path length of each internal passage is also
shorter, further improving air flow over a horizontal
design. The net effect is massive charge air reduction
but with improved air flow and less restriction
over a cheap horizontal core configuration intercooler.
Another important aspect of intercooler design
for the LS1 is the number of times the charge
air must change direction in order to enter and
exit the intercooler. Since air flow is momentum
based, each time the charge air must change direction,
it consumes energy - which results in high pressure
drop and reduced engine power.
With a horizontal flow core, the
velocity vector turns 90 degrees twice on entry
and again twice on exit. In addition, both turns
must take place inside the hight of the end tank.
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Front brace
between chassis rails not shown. Click for
large image |
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Front brace
between chassis rails not shown. Click for
large image |
With the APS vertical flow intercooler,
the velocity vectors turn only once over a very
wide distance on entry (up to half the width of
the core = 25/2 = 12.5 inches) on entry. This
allows the air to turn very gradually – a good
thing. Air flow is momentum based and the end
tanks on the APS intercooler are designed so that
an equal mass of air reaches each internal passage.
On exit, a similar situation exists however this
time, the air velocity vector turns 90 degrees
over a smaller distance (essentially the height
of the exit end tank. This is one reason why the
exit end tank is taller than the entry tanks.
Importantly, the APS intercooler uses the latest
in Bar and Plate core technology, not low cost
off the shelf tube and fin. Other than the fact
that the APS intercooler core boasts the highest
flow and greatest temperature reduction, the bar
and plate construction results in an inherently
strong intercooler core of high thermal inertia.
The advantage here for the performance street
car and drag race enthusiast is that with the
core's high thermal inertia, massive reserves
of cooling capacity are available in situations
where ambient air flow over the core is low. So,
after a power run to heat tyres prior to staging
for a quarter mile pass, there is plenty of intercooler
capacity to launch with full power at your disposal
- rather than forsaking power with a tube and
fin construction core that becomes heat soaked
during the initial burst.
Another aspect worthy of consideration is the
internal air passage cross sectional area and
fin arrangement of the APS Bar and Plate construction
in relation to tube and fin. The tube and fin
core has a 5mm edge boundary so for say a 4” thick
core, you lose half an inch in internal thickness
which impacts on passage cross sectional area.
In addition, the fins are extruded so they are
essential in a straight line and parallel to flow.
This means that the internal surface area presented
to the charge air is nowhere near as great as
that on a traditional bar and plate – which has
an alternating offset internal fin arrangement.
The result is the bar and plate core used in the
APS intercooler (which is actually an enormous
6" thick) flows better and removes far more
temperature than the traditional horizontal flow
tube and fin. These are just some of the reasons
for APS specifying this vertical flow bar and
plate core on the LS1.
That said, for other vehicles, other configurations
may be applicable, which is why taking a general
purpose core from one vehicle and using it in
another different type of vehicle is often fraught
with problems – even though the cores may be of
similar size.
The true dual entry design of the APS intercooler
system allows for the ultimate in true equal length
balanced ducting from each turbocharger to the
intercooler. This ensures the optimum utilisation
of the intercooler core by spreading the charge
air from each turbocharger evenly across the entire
intercooler core - This is efficiency at its best!
Intercooler ducting length is critical on the
LS1 in order to achieve balanced induction and
excellent driveability. By designing the turbocharger
to intercooler ducting specifically to be of equal
length, each turbocharger experiences the identical
effective air path to the intercooler which results
in totally balanced turbocharger performance (it's
like having two separate intercooled turbo systems
- one for each bank of cylinders).
Other systems that are designed with unequal
length, experience boost pressure and air movement
issues where under certain conditions, one turbocharger
pushes air back through the intercooler and into
the other turbocharger ducting. As air movement
is momentum based, this is simply wasted energy
that should be better put towards producing higher
horsepower, not restriction. In addition, these
systems of unequal length take the charge air
from one turbocharger all the way across the engine
bay to the other side in order to enter the single
air entry point to the intercooler. This creates
a massive restriction compounded even further
by having to turn the charge air almost 180 degrees
in order to enter the intercooler.
The advanced APS dual
entry intercooler not only solves this problem
but allows APS to utilize true equal length ducting
- the most efficient intercooler system routing
for the intercooled twin turbo LS1!
The APS intercooler core is of internally and
externally finned construction and offers significantly
enhanced flow and heat exchange performance, particularly
at high charge air mass flow rates (High boost
pressure and high engine power levels). Also,
unlike other manufacturers of intercoolers who
reduce cost by using low cost off the shelf tube
and fin cores, the APS drag race specification
bar and plate intercooler is designed with the
optimum ratio of intercooler core surface area
(1350cm2) to intercooler volume (20,250 cc) -
unlike inferior quality intercooler cores that
are very shallow (the APS core is 150mm deep!).
The result is an intercooler system with outstanding
flow and cooling performance, particularly at
high engine power levels of up to 820 kW (1,100
hp).
Front impact beam is retained with the APS Intercooled
Twin Turbo System
This
is the view from behind the impact beam - The
APS reinforced silicon duct that carries chilled
charge air from the mamouth APS intercooler to
the throttle body duct is cleverly incorporated
inside the front impact beam assembly.
However, there is more to intercooling than size
alone. Fully engineered light weight, cast aluminium
end tanks ensure optimum charge air distribution
throughout the entire intercooler core for maximum
charge air cooling and minimum pressure drop. After
all, everything about intercooling is achieving
the maximum charge air temperature drop with the
lowest possible pressure drop across the entire
intercooler system.
Click on the image to
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2004-2005 AutoTech Engineering