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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 33 mm. It is important to note that core area takes priority over core thickness. As a general rule, the core area in square inches should be greater than the engine displacement plus fifty. For example, the 3.2 S52 motor is approximately 200ci. In order for a radiator to efficiently cool this engine, the core area should be at least 250 square inches. The surface area of ZA's Alloy Radiator is 374 square inches.
ZA's Alloy Radiators also 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.
Cooling improvement also comes from larger radiant surfaces on the tanks. The alloy tanks themselves have a high level of thermal conductivity which helps to dissipate heat into air instead of back into the engine. In addition, the tanks on ZA's Alloy Radiator are larger than the tanks on a stock radiator. This results in a 65% increase in coolant capacity.
Empirical data speak to the efficacy of the Alloy Radiator. ZA's Alloy Radiator has been installed in front of super-charged and turbo-charged engines and has performed superbly. They are running in the hottest parts of the country - from California, to Texas, to Florida, in both street and race applications. ZA's Alloy Radiator also survived the twenty-five hour enduro at Thunder Hill. According to the driver, the radiator performed "flawlessly."
The E30 Competition Cooling Kit is designed for race applications where temperature
management is even more critical. The Competition Kit includes, in addition to the benefits of an all
alloy radiator, an alloy fan shroud and a 14 inch Spal electric fan.
The alloy fan shroud and electric fan * work in concert to provide maximum cooling efficiency. Simply hanging a fan on a core won't
do. The 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 a good practice. The alloy shroud in
combination with the electric fan creates a low pressure area in order to direct airflow over the entire core surface.
* The pusher fan mounts in front the radiator and eliminates air conditioning.
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