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OS 52 Surpass rpms, throw

Old 03-09-2005, 09:04 PM
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Default OS 52 Surpass rpms, throw

Hey gang,

Gettin back into flying gas again and I'm finally going to run this engine. I broke it in last year then stored it with marvel mystery oil while I went back to a basic electric trainer for a while. It's in a Sig 4*40 with a 11x7 prop running the recommended nitro % fuel.

Couple Questions:

-What kind of RPM range should I be looking for at low/high ends?
-How much should I set the carb to open to have a reliable idle?


Many thanks,

steve
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Old 03-10-2005, 11:12 AM
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Default RE: OS 52 Surpass rpms, throw

We usually prop the O.S. FS-52 Surpass to run close to 10,000 RPM or slightly higher. We see about 10,200 RPM with an APC 11 x 8 prop. Any prop that gives you that RPM and flies the model the way you like is correct.

We usually see about a 2 mm gap when the throttle's closed to idle. We start out wider and adjust as necessary to get a good idle that still gives good transition. You may wind up slightly smaller or larger. The exact distance isn't relevant. A good idle will be 2,300-2,400 RPM or lower.
Old 03-10-2005, 04:23 PM
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Default RE: OS 52 Surpass rpms, throw

Thanks Bax, that's exactly the info I needed. I had the carb closing to about 1 mm and it's why I could not get an idle last night. I didn't want to mess with it until I knew what I was doing. engines are an investment.


Wow, 10k rpm. That's a lot more than I got on my old 48 surpass back the last times I was flying! Then I was getting ~7400 rpm on a good day.


Time to go fly!
Old 03-10-2005, 05:23 PM
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Default RE: OS 52 Surpass rpms, throw

7,400 RPM on an FS-49 Surpass is REALLY low! We normally see 10K+! We use an APC 11 x 7 on the test stand.
Old 03-10-2005, 11:35 PM
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Default RE: OS 52 Surpass rpms, throw

Uhh... It wasn't a 49 Surpass, it was an OLD OLD OS .40 4 cycle, 1988/9 era. Before they started the Surpass. My last engine before I sold everything to go back to tschool and become an airline pilot.


Got 2 great flights in today before the wind kicked up. Engine flew great, I left it slobbery rich at 9,0something rpm. Great engine, great sound. Even left a pretty cool smoke trail because I was running it so rich.
Old 03-11-2005, 10:54 AM
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Default RE: OS 52 Surpass rpms, throw

Ooop! Should have said "FS-48 Surpass". O.S. never made a .49-size.

Pre-Surpass engine was only the FS-40. We'd see middle 8's with an 11 x 6 prop.

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