I originally posted the following question in the "Glow Engines" forum. I got some good suggestions, nobody really answered the question. It's more of a fluid dynamics question than it is an engine question. I don't know where else to ask, so I'll try here...

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Apparently I don't have enough outlet area in my .46-size World Models P-51 with an RCV-60SP. One of the "cons" of the RCV-SP engines is that they are more difficult to keep cool, as I am experiencing.

[link=http://image.rcuniverse.com/forum/upfiles/13495/Bz79072.jpg]Picture #1[/link] is how I cool the engine now. This is the side cross-section of the cowl. Engine is grey. Cowl is black. Cool air is blue. Hot air is red. The outlet:inlet ratio is about 2:1. But apparently the hot air doesn't want to circulate down like I want it to.

[link=http://image.rcuniverse.com/forum/upfiles/13495/Up49024.jpg]Picture #2[/link] is how I want to add additional outlet area at the top of the cowl.

The question is how big should I cut the lip at the top of the cowl? And what dimension should I use to calculate the additional outlet area?

In [link=http://image.rcuniverse.com/forum/upfiles/13495/Pu50610.jpg]Picture #3[/link], should I use dimension A or B to calculate the exit area?

Thanks in advance for your help.

Juice
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