If you design and tailored your cooling system for cooling in a steep climb on a hot day, you will have excessive cooling capacity at cruise (read - more cooling drag) than is necessary. 

Hey Ed,

I agree of course that you would have more cooling drag, but do you have any idea what the drag penalty would be for an RV style plane? 

I personally want to be able to climb at 100 kts, full throttle, on the hottest day, without ever exceeding any temps.  At the moment, I can, but the C drive and new prop may change things some.  I seem to have more excess water cooling, than oil cooling, and eventually, I may have to close up part of the radiator inlets.  

FWIW, the other day it was 92 degrees on the ground, and I climbed at 100 kts to 8k ft, full throttle.  The max oil temp was 195, and the max water was 178.  At 8000 ft, full throttle, temps settled in to be 183 for oil, and 130 for water.  That was at 196 mph TAS, with plenty of fairing work left to be done.  As for climb performance, I noticed that the EM-2 flight timer was on 7 minutes when I leveled out at 8k ft.  That's OK for now, but I expect to see that time to 8k ft be less than 4 min with the C drive.  

Rusty (just got home with a motorcycle, more like a training bike)