OS 46 with tuned silencer
09-15-2005, 01:13 PM
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OS 46 with tuned silencer
The manual for the OS.46FX says that for aerobatic airplanes it can turn an 11x8 thru 10 or a 12x7 thru 9 with a tuned silencer. Can you provide details of what silencer/header combo and set a what length this would be? I want to use the 46 on a pattern style airplane and am more interested in torque/vertical performance than speed.
The manual reference is at http://www.osengines.com/manuals/50s...1fx-manual.pdf, and is on page 12.
Thanks.
Jon Lowe
The manual reference is at http://www.osengines.com/manuals/50s...1fx-manual.pdf, and is on page 12.
Thanks.
Jon Lowe
09-15-2005, 03:41 PM
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My Feedback: (11)
RE: OS 46 with tuned silencer
We'd get a tuned-pipe system for a .46-size engine and then tune it to suit. Not sure what length to use because it will change for different props and fuels. Regardless of what kind you purchase, and what's claimed, a tuned system MUST be tuned to suit your engine, prop, and fuel combination.
Start with it long, start engine, peak the RPM with the mixture, and tach it. Kill the engine and shorten the header 1/4".
Repeat the above. If you see an RPM increase, shorten another 1/4".
Keep doing this until you see no RPM increase. Back off 1/4" and fly. Listen carefully to the engine. Land, kill the engine and shorten the 1/4" you backed off. Fly again and listen carefully. Did you get an increase in the air in level flight at full throttle? Then shorten 1/4" again after you land and kill the engine.
If you want the engine to be "on the pipe" only in verticals, then do your testing in verticals.
At full throttle, please remember that a tuned pipe system that's a bit on the long side will make the engine trend rich. If it's on the short side, the engine will trend lean. It's better to be a bit long than short.
You must stop the engine when you shorten the pipe assembly. "Tromboning" it while it's running will not give you a good set. The pipe must be warmed up by some running first. You can't tune a pipe by starting up, leaning, and taching right away. You need some running at full throttle to allow the pipe to warm up as much as it's going to.
If you change to a different size prop, or even a same-size prop of a different brand, lengthen the assembly and retune it. Change fuel to a different nitro or oil blend, and you'll likely have to retune the pipe.
Start with it long, start engine, peak the RPM with the mixture, and tach it. Kill the engine and shorten the header 1/4".
Repeat the above. If you see an RPM increase, shorten another 1/4".
Keep doing this until you see no RPM increase. Back off 1/4" and fly. Listen carefully to the engine. Land, kill the engine and shorten the 1/4" you backed off. Fly again and listen carefully. Did you get an increase in the air in level flight at full throttle? Then shorten 1/4" again after you land and kill the engine.
If you want the engine to be "on the pipe" only in verticals, then do your testing in verticals.
At full throttle, please remember that a tuned pipe system that's a bit on the long side will make the engine trend rich. If it's on the short side, the engine will trend lean. It's better to be a bit long than short.
You must stop the engine when you shorten the pipe assembly. "Tromboning" it while it's running will not give you a good set. The pipe must be warmed up by some running first. You can't tune a pipe by starting up, leaning, and taching right away. You need some running at full throttle to allow the pipe to warm up as much as it's going to.
If you change to a different size prop, or even a same-size prop of a different brand, lengthen the assembly and retune it. Change fuel to a different nitro or oil blend, and you'll likely have to retune the pipe.
