![]() The use of a cowling can be problematic as encompassing the entire rear radiator core can inhibit air flow at speed. With a clear air intake in front of the radiator driving above 60kmh a fan is not as necessary. While driving at speeds of 60kmh or under, electric fans are most effective due to their total operating independence from engine revs. Australian manufacturer, Davies Craig publishs all the specifications and dimensions of the entire range of 12v & 24v Thermatic Fans and Thermatic Switches on their website, Some electric fan models may be enclosed in a metal or nylon cowling (sometimes referred to in some circles as a shroud) which is purposefully designed to be mounted on the rear of the radiator, only. Attention should be given to the power (watts) of the fan motor and the published (CFM, Cubic ft 3/min), wind force the specific fan produces, usually the larger the electric fan the higher the CFM. All modern electric fans are supplied with a standard circular shroud to maximise efficiency. Nearly all modern-day vehicles have an electric, temperature-controlled fan installed as standard equipment at the rear of the radiator. For this reason, thoughtful consideration should be given to vehicle’s use for both low speed cruising and higher speed operation to ensure the effective channeling of air to the radiator while operating in both circumstances. If there’s a buildup of air pressure in the fan cowling or engine compartment, air flow across the radiator can stall, causing higher engine temperatures. The higher pressure is used to drive the air through the radiator core. To function efficiently the air stream on the front side of the radiator/needs to be higher than the air stream behind it. Hence the installation of a temperature-controlled, radiator mounted electric fan, in the majority of cases, as a replacement, is far more efficient. Some OEM mechanical engine-driven fans can reach a blade stall at high RPM, causing a ‘wall’ that prevents air from passing through it. The blades should have no more than 1” clearance to the shroud. Engine-driven fans MUST have a circular shroud to be fully effective. The next issue relating to air flow that requires serious attention is the fan. Scoops, lips, deflectors and recessed panels can be used to improve air flow when the frontal area of a vehicle is less than ideal. Ideally, the radiator needs to be squared up to the air. The front opening, air intake is one key aspect to its performance. A radiator needs to have a solid and consistent stream of air passing through it on most occasions while the engine is in operation. Maintaining adequate air flow at various speeds is essential and can be complex. For this reason, one of the most crucial factors in a cooling system is ensuring there is adequate and efficient air flow lack of air flow can affect the effectiveness and efficiency of a radiator and indeed the longevity of an engine. One fact is, we have never had any calls on any level complaining of too much air coming through a radiator core! The purpose of a radiator is to assist with the transfer of heat from the core to the air via the coolant flow to and from the engine. Many a debate has been held relating to air flow in an engine’s cooling system and what is an adequate volume of air and what is not.
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