I opened up my cowl bottom after the first few very hot test flights. After adding a second oil cooler and opening the bottom now I have the temps within sensible limits but still need/want cooler. Question now is open the cowl exit opening up a little more or adding a lip to the exit. I personally am skeptical that a lip does anything other than add drag but I will put it out for opinions. Has anyone really seen the lip positively contribute to cooling? Should I add the lip or no lip and make the hole a little larger? This is all voodoo science to me at this point. I have read all the NASA reports and such. Most of those deal in cooling drag and speed. At this point I just want controlled cowl temperatures.
Add a lip or make the hole bigger? Or both?
Before I cut the hole I was near 1:1 inlet/exit ratio. Now who knows because it is very difficult to get a good measurement.
