Old 11-10-2020, 07:13 AM
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Originally Posted by tedsander View Post
I doubt you'll ever get an answer. Too many variables peculiar to each setup to give a meaningful guide. Particular engine design, prop, fuel, cowl shape, entry, exit, smoothness of the airflow, ambient temperatures, humidity...the list is almost endless. Best you can do is be as empirical as you can be - give it as much as the practical configuration will allow. If it gets hot, modify for more, play with baffles, run richer, or whatever it takes. If you have a way to measure temps, so much the better.....
Excellent answer. Especially the part about too many variables. I am (or was) a mechanical engineer, and even though I have forgotten much of what I learned 35 years ago, I never would have been able to look at even my own plane and crunch any numbers to calculate anything. But I could look at my entire situation and "eyeball" the best scenario to cool it.

Do make certain that the exit area is larger than the intake area. If not, then increasing the intake area will accomplish essentially nothing. In other words, the controlling factor in cooling is the exit area, not the intake area. Make both as large as feasible, while concentrating more on the exit area.