ENGINE COOLING

[N942R]

MOST RV's do not cool properly.. There Iv'e said it... Depending on where you live most RV's do not cool adequately.. Ya we douse them with 100LL or climb at high speeds or reduced power and deal with it... The problem is that the Van's baffles do not allow the lower aft one fourth of the rear cylinders to get any or enough air... Also to a lesser extent the front lower one fourth of the front cylinders are not doing much better... Some have tried to add exit air which will
help a little just because the rest of the cylinder gets a little more air but does not
solve the problem...
Take the time and go look at the baffles on an old 60's Cherokee and you will see that they addressed those areas way back then... An instructor and student can beat up on one of those all day long without getting hot.... Ya they have a larger
opening but also going much slower so not much pressure..
The RV's need a duct down the back side of the right baffle and forward under the lower fin area of at least 1.5 square inches and the existing wrap removed from just below midpoint of the cylinder... Also the it needs a duct down the inboard side of the oil cooler and then forward under the fin area. Also 1.5 square inches and the wrap removed... Then holes cut in the baffles above to admit air into the
ducts of at least 2 square inches..
The front cylinders need almost 1 square inch down to below the midpoint of the cylinder and into the wrap..
For your information, I have built 7 RV's of different models, have around
1000 hrs in them, and have been around big bore Lycomings almost since they were first introduced.:: without divulging my age!!!!
It is a lot of work but these engines are expensive and we are kind of relying on them to stay healthy... I have seen 25 to 30 degrees F. decrease in head temps

[DanH]

Yep, you're right

[F1R]

Some sketches or photos of your detailed solutions would be appreciated beyond words.

And if that is too much work, just mail them to Dan Horton and he will post them give you credit.

[DanH]

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[N942R]

As I said in the original post, it takes 1.5 square inches to feed those 1 1/4 deep fins below. Ya cant do it with a 1/16 or 1/8 space into the "wrap" or adding a washer to leave a little space... If you want your engine to be cooled properly you just need to bite the bullet and spend a day or three making some ducts to feed air down there... You will think you are flying a different airplane..... Re read my original post. It works.... The RV cowls have plenty of inlet and outlet area without luevers or cowl flaps or lips added on to them... Ya spent a year building an airplane, what is another day or two making the engine happy.....
High oil temps are usually the airplanes with oil squirts on the cams or pistons.
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........
Please go look at an old Cherokee and it will be plain what to do... They are lots of them setting around and the old ones with the metal cowl can be opened up easily so you can see... They left the front baffles below midpoint of the cylinder
so they can get air down there..

[Toobuilder]

Yes. Preaching to the choir.

http://www.vansairforce.com/communit...&highlight=CHT

[erich weaver]

Originally Posted by N942R

High oil temps are usually the airplanes with oil squirts on the cams or pistons. 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

Would like to see pictures if available. Are there Naca ducts readily available that are large enough for this? Wouldn?t such a set up mean that the duct has to be disconnected every time the lower cowl is pulled?

Thanks

Erich

[gmcjetpilot]

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.

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Car guys also debate the Scoop vs (submerged) NACA