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Old Dec 30, 2012, 05:19 AM
Registered User
Denmark, Capital Region of Denmark, Frederiksberg
Joined Dec 2009
16 Posts
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G-Loads

Hi Guys,


Is there someone who can tell me how to fix a problem with my OS 40FX,

I have installed the engine in a home construction of an airplane built for speed, the plane flies very well, but I have a problem with getting my engine to run smoothly under G-loads, as long as i fly straight and level it spins like a dream, but when I make abrupt pitch changes or tight turns (High G-loads) the engine hesitates until I ease the stick and letting the G-load drop, then it is back in the zone in a flash.

The engine swings a 8x8 or 9x8,

Why is this ??. Wrong level of the fuel tank in relation to the carb is my guess but I don't know

Thanks


Ulrich
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Old Dec 30, 2012, 05:24 AM
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gene6029's Avatar
Wilson NC 27896
Joined Apr 2009
739 Posts
Are you running a Jett bubbless tank? Sounds like fuel starvation. You might want to ask some of the pylon raceing guys this question.....Gene
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Old Dec 30, 2012, 05:32 AM
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Denmark, Capital Region of Denmark, Frederiksberg
Joined Dec 2009
16 Posts
Hi Gene, thanks.

No just a regular rectangular plastic fuel tank with a clunck in it.
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Old Dec 30, 2012, 06:08 AM
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United States, CO, Elizabeth
Joined Oct 2006
13 Posts
I had that same problem when I flew a modified scat cat with a
Rossi as a power plant back in the day’s.
Ended using a setup with a pre tank kind of like a hili to get rid of air and have positive feed.
If it seems like the engine runs better as the tank gets empty id raise it up more.
I also have used a small ID line from last tank to the carb to reduce air and syphon back.
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Old Dec 30, 2012, 09:19 AM
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downunder's Avatar
Adelaide, South Australia
Joined Sep 2003
3,051 Posts
Try setting up your tank as a Uniflow which is simply done by having a clunk on the end of the breather line so it can follow the normal clunk feed to the carb.
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Old Dec 30, 2012, 10:16 PM
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Joined Jun 2008
177 Posts
Quote:
Originally Posted by ubihof View Post
... the engine hesitates until I ease the stick and letting the G-load drop, then it is back in the zone in a flash.
Ulrich
Perfect indication that you are too lean. Open the high speed needle valve a few clicks until the hesitation goes away.

A Tetra or Jett bubble-less tank prevents this from happening. But for sport flying and entry level pylon racers, just open the needle valve a few clicks.

Kurt
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