ORIGINAL: ryanofoz
Engine gurus!
I just finished a SIG Rascal 40 and used an OS 46 LA engine. The problem I seem to be having is when I point the nose up to test the air bleed, the RPM always increases. If I point the nose down, the engine will stop. Doing this at full throttle, up is fine, down shuts down the motor. I have opened up the air bleed to a whopping 7 turns out from closed and it still acts the same. It seems unaffected by any change in the air bleed.
Throttle response is fine from idle to WOT. If I leave it idle for long the engine will quit as well. I dont have it to low, its a mix issue for sure. I have about 3 tanks of gas through it so far and it keep acting the same. I would like ot fly but as-is I am worried if I dive or loop under power I will dead stick. I am not new at this and have 4 other planes that work just fine. I am just missing something here. Are there any known issued with a LA engine and running inverted?h
Any ideas? The only different thing is that I have the needle valve off the motor and screwed to the firewall so the needle can be turned from the bottom of the plane. I dont see how that could so it but you never know.
Any help would be great. I want to get this bird in the sky!
Ryan
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What you are describing is completely normal for a new engine with only three tanks of fuel through it.
Also, it is normal for the engine to speed up when the nose is raised while being held on the ground. Most engines will remain running if held nose low, but this is something that gets better and better with more running time on the engine. The carb on the OS.46LA is a good carb. Not to worry.
When the model is descending, the fuel inlet is seeing less than 1 gravity's (G) worth of pressure from the fuel tank, so when flying, the engine should not quit from being flooded.
We hold the nose upwards and adjust the high speed needle for a slightly rich mixture with the engine pointed vertically upwards. This ensures that we have enough fuel at the end of the tank to run the engine safely without going to lean. The variations you are seeing in mixture are perfectly normal for a suction fed glow engine and should not be considered a defect. The engine's running will improve considerably as you accumulate more running time.
Good luck with your Rascal 40. I have the ARF Rascal 40 NIB here and am about to get started assembling it. Sure is a pretty model.
Ed Cregger