I have an OS .91FX in an Aeroworks Edge 232 40/60. I have been struggling with this engine all season over heating. I have worked with several club members that are very experienced in trying to get this motor to run still no success. I am convinced this motor is cursed and needs to be replaced. I would like to hear any recommendations for motors that run well being enclosed and can handle the additional heat inside a cowl.

All engines need proper cooling.
Read this, which may be an alternative to replace the engine, just to end up with a similar problem:

http://www.prme.nl/forum/viewtopic.php?t=148

I run an OS 120AX inside a cowl and have no overheating issues. There's the rule of thumb saying that you should have 3x exit area than entrance area. I have a hole cut the size of the engine head in the side of the cowl. It's a Yak with a relatively large open front. Also some cooling down by the muffler.

Prop, fuel, plug, and tuning have a lot to do with it. Try a colder plug.

Ducting the airflow over your engine head is also effective.

Joe, this is something I have considered doing. I have tried most other options with little success. More info on what I have done - the exit is opened to at least 3 times the size of the intake. The exhaust is exposed. Checked for leaks have adjusted low and high speed needles. Engine is running rich with a nice stream coming from the exhaust. I have removed the baffle from the exhaust. If anyone has photos of different baffle techniques I would love to see them as I would try this as a last resort.

The exhaust size sounds good, but won't be worth spit if the opening faces the oncoming air. You can have as little as 1.5X intake for exhaust (obviously less than the 3X) if the exhaust is in an area of negative pressure. For example, when cowl flaps are open on a Corsair/Hellcat/P47/etc the area behind those flaps is definitely negative. Truth is, any opening that's "behind" anything will work well to extract. An opening in the fuselage when the fuselage starts to taper down would be an example.

Another thing that hurts cooling is having open area that isn't in front of what you want cooled. Let's say that again: Another thing that hurts cooling is having open area that isn't in front of what you want cooled.

Cool air moves easier than hot. So the cool coming in that doesn't run into something to cool stays cool and moves past anything that tends to block it. Like the hot air around an engine. Which is hard to move, harder to move than cool. So the cool moves around it and finds the exhaust opening and leaves. It uses up the capacity of the opening while doing it. So the hot air around the engine gets blocked from leaving. And gets hotter. and hotter. and harder to move. and can't move cool air anyway.

See the two openings in the Skybolt? One has a baffle that angles incoming air toward the engine. That air would actually hurt the engine cooling if allowed to move straight back to the exhaust opening. The baffle took about 10 minutes to fit into that cowl. That engine runs like gangbusters, and the exhaust is maybe 1.5X the intake.

Here is an example of a really blocked intake.

The red circles show where the first openings were. That's an OS91FX with Slimline Pitts muffler in that cowl. And H9 designed that cowl to SEAL COMPLETELY to the fuselage. No exhaust openings at all. Anywhere.

So I cut some exhaust openings that opened into negative pressure. The engine had minor problems on the hottest days we recently had. So I blocked some of the first openings. Put a baffle right up to the engine where the blue circle is.

All the air that comes into that cowl runs right into the engine or muffler. No air that gets in can bypass something that needs cooling.

It flew without problems the last few outings when the temps were in the high 90s. Since then, I had nothing to do one evening and increased the "negative" shapes for insurance. I basically cut the closed cowl flaps and opened them. It's more scale too. I like that. MOF, that bird is growing on me more and more. Probably partly from having those extra details. And the way it flies.

My Corsair hits pretty close to 100mph. I can't wait to clock that Hellcat.

Here are some better pictures of how the Hellcat's cooling evolved.

Those vents are actually where the full size Hellcat's have vents. The picture shows the right side, behind the engine. The left side hasn't gotten the full treatment because it's not behind the engine and the engine doesn't need more cooling.

The baffle is the black that comes right up to the engine. It is styrofoam insulation painted black. Pink looks funny inside a WWII cowling. It's glued to the inside of the cowl.

I had trouble with a 91FX and was ready to throw the towel in, but I kept fighting it. Here is what I finally had to do to keep the engine cooled as needed and now she runs fantastic. The vent and cowl plug is made from a plastic fuel jug I just cut up and fitted as needed. Hope this helps you out.

Two different types of planes, apples and oranges but you can see how it was done, I added some white paper so you can see the cooling air flow. Extra 300, bottomg of the cowl has been cut a lot. Pattern plane, the fuse was designed for a tuned pipe and the air flow goes right on through the cowl and out through the groove. Like Joe mentioned, you must get the inflow out of there taking the heat with it. 1-3 is about normal for good cooling. I have a friend that hates to cut up his cowls so he opens just a little then opens more as he flys his plane until it quits over heating. Try your plane/engine without a cowl and make sure cooling is the problem before you start cutting. It may just be a tune problem?

3 different modelers, all did the same. Directed the air to what needed cooling, and helped it out.

Just cutting holes doesn't hack it.

Thanks for the information. I am going to re direct the air flow over the engine and see what the resuls are. I hope this takes care of it. I like OS engines and this is the first one that I got that is tempermental. It's been frustrating to say the least.. By the way thanks for the pictures it shows good ideas. I would never have thought of using insulation as a baffel!

I have made directional baffles from light ply in Sukhois or just made scoops from balsa wood to direct air flow. If you fly your plane without the cowl it will let you know if that's the problem before you start changing things. That's where I would start. If you still have the problem it will lead you to look in other places.