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OS 160 FX Mid-range tuning

Old 09-05-2006, 03:45 PM
  #1  
rubezahl
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Default OS 160 FX Mid-range tuning

OS 160 FX Mid-range tuning

I am having problems with tuning my 160 in the mid-range. I fly it in a GP Super Stearman. The engine is turning an APC 18x6 on Powermaster 15% with a pitts style muffler and I believe it is has an OS "F" plug, but i'm not sure. When i let the engine run at 50% power for a minute or more it loads up. When I apply full throttle the engine stutters and belches out a puff of smoke. Sometimes it dies, sometimes it stays running. I was using a Perry shaker pump, but i have disconnected it now because it did not make any difference. I would like to run the engine without the pump, if possible. My hunch is that the low-end is too rich, however, i don't want to run it too lean and potentially damage the engine. I had this engine in another airplane and it was trouble free. Could someone provide me with some insight and/or instructions on how to sort this out? Any assistance will be greatly appreciated.

Sincerely
PB
Old 09-06-2006, 01:23 PM
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Bax
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Default RE: OS 160 FX Mid-range tuning

Start out with the low-end too rich. Get the high-speed needle set correctly at full throttle as the first order of business. Then work on the idle mixture. If the midrange is too rich, then you can afford to lean the idle a bit. You won't damage the engine if the idle mixture's too lean. The engine will just quit running if you have it too lean. As long as you get a good idle and acceleration, you're not too lean on the idle mixture.

You'll likely have an easier time if you go to a fuel with 10% nitro. 15% can cause problems in larger engines. You may also be trying to idle the engine too slowly. Anything lower than 2,500 RPM would be considered 'good'. If you have to increase idle RPM a bit to get a good idle and midrange, then that's what you have to do.
Old 09-24-2006, 01:05 AM
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rubezahl
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Default RE: OS 160 FX Mid-range tuning

Bax,

I heeded your advice and purchased some 10%. I ran the motor today and it seems to have solved my problem. I set the low end mixture back to factory and left the high end alone. After running for 5 minutes at 1/2 throttle, the engine transitioned to full without a hitch. I tach'ed the high end at approx. 8500 RPM and the low end at just under 2500 RPM. I noticed that there was some fuel leaking from the cylinder head, so my compadre tightened down the cylinder head screws and that seemed to solve that issue. Next weekend I'll take her out and see how she does in the air. Thanks again for your assistance.

PB

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