PJC

AM-
I have an OS 160FX. Have the low and high needle set so it idles/transitions/high end great. Engine is running perfectly. My problem is at 2/3 of a tank on any down line at all with a reduction in power she leans out fast (.5 seconds) and cuts out. Not running hot and overheating but cutting out. I have it in a DPM 330L with a bisson Pitts muffler and a 24oz great planes tank. I am using a fill line to a fuel dot, a muffler vent line with a T to a fuel dot, and a straight line to the needle valve from the tank. The clunk is a large clunk on a piece of large blueline fuel tubing, actually large fuel tubing on the whole system. Seems to me to be a delivery problem. Would a 1-2 oz header tank help this situation, or should I go to a pump of some sort. The clunk is not getting stuck it hangs about 1/8” from the back of the tank and moves freely from corner to corner. The large line is a bit stiff, but I can not imagine with the large clunk the clunk is jumping out of the fuel. I just replaced all the lines, and have not re-run, but would appreciate any insight you may have for me.

Thanks,
Jeff

amcross

My Feedback: (2)

Jeff,
I really suspect the problem is the pitts muffler and insufficient back pressure, but let me check with a few other minds and get back with you...

PJC

I appreciate you researching it for me.

Thanks,
Jeff

amcross

My Feedback: (2)

Hi, Jeff! Some other thoughts for you...

On a down line, is it possible that the fuel pickup in the tank is becoming unported? This would cause immediate fuel starvation, which would explain the leaning and cutting out. If the model needs to be brought to level flight before the engine comes back in, I'd strongly suspect unporting.

Also, when a "downline" is referred to, it a vertical or nearly so? This would leave 1/3 of the tank empty at the rear, and the clunk line sticking into air. Most modelers don't use extrememly flexible clunk lines so that they won't get stuck in the front of the tank on spins, snaps, noseovers or other sudden stops...and therefore the clunk can not move to the front of the tank for proper fuel pickup in a downline scenario.

PJC

That is precisely what I was thinking and why I was going to put a 1-2oz header tank. Unless someone makes thinner walled large fuel tubing. When I say down line I am refering to even a gradual dive. Maybe the clunk needs to be bigger? I will work on it and let you know my results. If you have any other insights I would appreciate them.

Thanks,
Jeff

amcross

My Feedback: (2)

Hi, Jeff! The header tank would likely fix it for you, assuming that's the problem, yes. I don't recall whose line we used to use for the gas birds that was also glow safe but it was VERY flexible. I'll try and find the name for you.