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OS 1.40rx Temperature

Old 07-05-2013, 07:43 PM
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Default OS 1.40rx Temperature

I have an OS 1.40rx in a pattern plane I bought used and I would like to know what engine temp it should be running at and what is considered too high.

During my most recent test flight the max head temperature was about 250 deg F with the cowl off and about 310 deg F with the cowl on. This last flight was with a 16x10 prop, Cool Power 10% glow fuel, and it flew 9 minutes without dieing, with the cowl on. I used Omega temp strips that I stuck to the sides of the head. They record the highest temp within 10 deg F. It handled the 310 deg F temp - but I am nervous, that seems high to me.

There is some history but in summary I have had trouble with the engine dieing inflight with the cowl on and I assume it is due to over temp. The plane flies about 4 minutes then dies. Currently running a 16x10 prop. My last test that ended in a dead stick landing was with a 16x12.

Jim West
Old 07-08-2013, 06:22 AM
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Default RE: OS 1.40rx Temperature

It's not possible for us to give you an actual temperature or temperature range for your engine. The specific temperature is determined by too many factors. There is only one way to determine at what temperature your engine should be run. You have to run it first and then find out what temperature the engine reaches.

Make sure your engine is operating properly with the performance you expect. Use the exact setup every time...fuel, exhaust system, plug, measurement location, and so forth. If you change anything, the temperature will change. Once you have the engine running the way you want it. Take your measurement. This is your starting point. You will have to take measurements over time to find out how the weather affects it. As the air temperature and humidity change from day-to-day, the operating temperature will change. Eventually, you'll find a temperature range that you can work with.

Engine temperature is not an absolute number for setting your engine. It is only a guide, and can help alert you to potential problems. The only sure way to make sure your engine is running correctly is to see how it's running. An engine can be operating at "correct" temperatures, but not running well.

Finally, use any temperatures you read about, or people tell you, as rough information. The only useful numbers are the ones you actually measure when your engine is running correctly. If your engine is running correctly, then what you measure is correct, even if some else says it's too high or too low. Don't worry about the differences. Each engine is in a unique installation with a unique set of circumstances, so there can be wide variances in engine temperature.

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