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A
number of things contribute to cooling efficiency, e.g.; fluid
capacity, fin design, material, etc. Zionsville Autosport's Alloy
Radiator has a core thickness of 43 mm. The surface area of ZA's
e38 - e39 alloy raditaor is 376 square inches - the same as a
stock radiator. 
Additionally, we use a high efficiency core similar to a stock
radiator. High efficiency cores have more fins per inch, more
tubes per core and more cooling capacity. Each row has a single,
large tube. The flat side of the tube is in direct contact with
the fins which transfers heat from the tube walls to the fins.
Since the rounded ends of the tube are not in direct contact with
the fin, this portion of the tube does not aid in secondary
cooling. The more tubes per row, the more rounded ends, and the
less direct contact there is between the tubes and the fins. ZA
uses a single tube for better heat dissipation.
The
E38-E39 Super Duty Cooling Kit... The alloy fan shroud and
electric fan work in concert to provide maximum cooling efficiency
by pulling 2070 cfm through the radiator core - even while sitting
still if required by engine temperature. * Simply hanging a fan on
a core is inefficient as airflow must be directed through the
entire core area, not just directly in front of the fan. The
latter approach limits the effectiveness of the core. Essentially,
it reduces the core size to the diameter of the fan. Not to
mention the fact that hanging a fan through the core will
eventually fatigue the cooling tubes and lead to failure.
The alloy shroud in combination
with the electric fan creates a low pressure area behind the
radiator in order to pull air through the entire core surface.
(The front of the core is exposed.) The concept is a refinement of
the BMW design. Our kit features improved sealing of the shroud
and increased air flow without the parasitic drag of an
engine-driven fan. We have also been advised by both customers and
technicians that the engine fans are disintegrating at around 100k
miles, taking out the cooling system and damaging the hood of the
car. Our design incorporates a caged electric fan with a safety
shroud and lighter weight individual fan blades. The result is
improved safety and efficiency.
With regard to the expansion tank,
we have been advised and personally experienced tank failure
through rupture of the main expansion tank. Our thinking is that
due to higher heat soak temperatures on V8 and V12 cars, the tanks
are heated/ pressurized beyond their limits. As a result, we
designed an alloy expansion tank with greater resistance to
degradation caused by the more extreme temperature limits in V8
and V12 cooling systems. Our tank does incorporate some of BMWs
features; e.g., we retain the original cap and the internal
plumbing. The cap design is very clever: it facilitates the
expansion and contraction of coolant, while at the same time
offering an escape route for atmosphere and coolant when pressure
in the system threatens passenger well being ** and cooling system
integrity. The topping off process requires filling the tank until
one half the level is maintained during the initial fill, then
topping off after a driving cycle, once the cooling system is
cold. As in all our radiators, the alloy construction of the
radiator also improves efficiency through an increase of radiant
surfaces and enlarged storage capacity.
* We offer multiple heat range
temperature switches for custom tailored fan control.
** Otherwise, the heater core could rupture and spray coolant
inside the passenger compartment.
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