How much air is needed for proper engine cooling?
I did a search on this but couldn't find much and wasn't sure which forum to post this in so apologies in advance. Anyways, is there a rule of thumb to determine the volume of cooling air needed for proper cooling of a particular 4 stroke glow engine? I don't mean the rule where you need approximately 3 times the air exit area versus the intake area on cowled planes for instance. I mean how much cfm of air must flow past the cooling fins to satisfactorily cool a given 4 stroke? Or to put it another way (all things being equal) how do you determine the size of the opening in the cowl needed for sufficient cooling?