have a Stinger 20cc twin on a Balsa USA Phaeton 90. Engine runs great. Initial flights were sloppy rich. As I leaned it out, it would dead stick after about 3-1/2 minutes in air. I would bench run it, tune it slightly rich high and low end. I can run it on bench indefinitely, any angle any throttle setting. Get it in the air and 3-1/2 min it dies. I checked everything I could think of.


It really seemed like maybe the piston was dragging so I added oil. No help. I began thinking about the cylinders sticking out in the airflow. I theorized that when the engine gets warm, the pistons expand but the aluminum cylinder heads in the airflow do not. I made a simple deflector to cut down direct airflow to heads. Now the plane runs in the air indefinitely. I thought I would pass it on in case others have similar issues:

Now that is thinking outside the box!

Looks to me like you do not have much air flow over those jugs.
I have no idea as to what your 3 1/2 minute wall was all about.
There is no arguing with success though.

It's more airflow than it seems; it's just not direct. The air still comes around the plates and there is a lot of fin area which on some airplanes is all cowled up. The aluminum cylinder head transfers heat really quickly either in or out. Direct air was super cooling it keeping it from expanding with the piston.

The next step for me, not that I have too, is to vent more air from the cowl itself or the center part of the engine. I have louvers on order for the cowl.

Also worth noting, a typical car engine has the least cylinder wall friction around 210°. I know this is not a car engine and is apples to oranges however, engines running too cool and tight can cause high wear and problems. My goal would be to even the heat out.

One more thing, I like how you sneaked the TA in the picture (just an accident I'm sure wink wink).

lol

Here, is this a better photo of the cowl? It's been my distraction from RC over the years.

Yes, that is a better picture. I love that t-top Olds, what a classic beauty!
In the toy race you are really making an effort. Thumps up

Well I'm trying to thin out. Want a NASCAR? LOL