Originally Posted by N942R
On those I have mounted the oil coolers on a NACA duct on the "Right side" of the cowl which will solve that problem.. Nothing wrong with the coolers... But that is a separate issue.
Submerged NACA ducts are problematic for an oil cooler, many test, experience, articles has shown this success is not automatic with a NACA scoop. Love to see your whole NACA oil cooler set up.
1) NACA - you can also cause overheating by pressurizing the lower cowl with your NACA scoop if the oil cooler is dumping air back inside the lower cowl.
2) NACA can flow volume when there is little to no resistance and lower pressure at discharge. Dave Anders wrote an article in Kit plane (Oct 2018 Optimizing Induction Air Fine-tuning intake system runners for increased performance and economy. Speed with Economy, Kent Paser wrote about NACA scoops more enthusiastically in his classic book. However they are not magic and often implemented, located and used incorrectly. They always look "cool" but they are no free lunch. They do add drag and may produce very little airflow unless you do everything correctly. You might be better off with an external scoop and take the drag and get real RAM Pressure, with a discharge separate from lower cowl plenum. Many planes like the DC-3 has the oil cowl completely outside the cowl. The cooler needs high delta P to flow air and NACA scoops don't create pressure but flow air, at lower pressure head. Add back pressure on the exit side of the cooler inside cowl you may end up with no flow or reverse flow.
Car guys also debate the Scoop vs (submerged) NACA