Originally Posted by Jeremy Gilbert
Originally Posted by Daren Peacock
On the other hand, I have not specifically tested myself but once you get up to a certain speed, the air forced through the rad because of the airflow against the rad, should be greater then what the fan/fans can pull through. At this point, that shroud should be blocking airflow. This is why fans are really only needed at low speeds/stop & go traffic.


This is actually a common misconception. If you have sealed ducting in front of the rad, then what you said would be true. However, at speed, it is still more difficult for air to go through the rad than around it. Without sealed ducting FORCING the air through the rad, it will still predominantly go around. However, at speed, there is sufficient airflow moving across the front and around the rad to pull heat away; airflow which is not present at low speeds/stop & go traffic, giving the results that have falsely been attributed to air moving through the rad.

I have done quite a bit of testing with this over the summer. The results have been quite staggering.


Curious as to what you have done for testing?

What's the misconception, I did specifically say that airflow will always take the path of least resistance & in order for it to benefit from the incoming airflow, the rad must be sealed?

I haven't done anything scientific, but when at highway speeds turning the fans on/off via link made no difference that's loggable with the stock ecu. So that would seem to tell me the cooling from incoming airflow is greater then what the fans are able to achieve (whether its through the rad or across the surface). I do run aftermarket fans, but they are about as big of fans (ie move the most airflow for their size & do the best as static pressure increases) as I could fit. The AC fans is ~1300cfm & the main fan ~1800cfm, which probably aren't too far off from stock.

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