OS 91 Surpass II Max RPM and Tach Setting?
01-31-2004, 08:03 PM
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OS 91 Surpass II Max RPM and Tach Setting?
I need to know what is the maximum RPM that is safe to use this engine at (of course RPM's being tached on the ground)? Also, so what's a good safe high needle set RPM backed off from the maximum RPM setting as to keep the engine running safely rich once the plane is airborn?
Thanks,
Dennis
Thanks,
Dennis
02-02-2004, 12:30 PM
#2
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RE: OS 91 Surpass II Max RPM and Tach Setting?
We usually prop the O.S. Max FS-91 Surpass II so that it's running in the mid-9,000's. We use an APC 12 x 10 prop on the test stand. Target that RPM range, and you'll be OK. Select a prop that will turn that RPM range on the ground and fly your model the way you want it to fly.
As far as needle settings are concerned, we NEVER count turns. We use a tach to lean the engine to peak RPM and then richen a few hundred. We then listen to the engine in the air to see if it's too rich or too lean. A good way to approximate teh correct needle setting is to fill the tank only 1/4 full, start the engine and open it to full. Lean the engine to peak and richen a few hundred RPM. Hold the model with the nose straight up. Adjust the needle as necessary so that it's still rich of peak RPM. Then put the model down, kill the engine, fill the tank, and go fly.
As far as needle settings are concerned, we NEVER count turns. We use a tach to lean the engine to peak RPM and then richen a few hundred. We then listen to the engine in the air to see if it's too rich or too lean. A good way to approximate teh correct needle setting is to fill the tank only 1/4 full, start the engine and open it to full. Lean the engine to peak and richen a few hundred RPM. Hold the model with the nose straight up. Adjust the needle as necessary so that it's still rich of peak RPM. Then put the model down, kill the engine, fill the tank, and go fly.
