stunthanger.com
Engine basics => Engine set up tips => Topic started by: Ken Cerny on May 17, 2009, 03:52:31 PM
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???
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The probable cause is something with the tank, but it's impossible to guess just what without more info. What's the engine doing? Surging? Going lean for a long time? Burping (different from surging)? Give us a clue . . .
Also, what kind of tank? Are you using a fuel filter? Have you cleaned the filter? What prop are you using?
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1) Are you sure the leadouts are in the right position? If they're too far aft, the fuel runs to the front of the tank. The engine hickups, the nose comes in, the fuel has moved to the back of the tank, etc., etc. Fix the LO's!!!
2) If you can, shim the back of the tank outboard.
3) If it's a clunk tank, taper the clunk so it picks up all the fuel.
Some combination of these will most likely fix the problem. n~ Steve
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Ok...I'm running a 12x6.5 Bolly three blade prop with a regular plastic clunk tank. My tank is shimmed back end outboard. Towards the end of the flight the engine tries to suck out every bit of fuel like it can't decide to shut off or keep running. I took the tank apart and shaved the clunk as suggested. The weather is not good in south Fla the next few days. But when I get a chance to try it I'm sure the clunk shaving will work. But if anyone has some other ideas please feel free to send them. Thanks for the input. mw~
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Also the fuel filter is always cleaned and the lines are in the best position for the plane. They are about in the middle close to where the Legacy plans suggest. I'm using OMEGA 10% with an ounce of castor added. The engine uses only 2 3/4 ounces and gets me about 7minutes.
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#^ #^ And the winner is.....Steve Helmick for suggesting that I taper the clunk. I did so and WOW! Works great. The engine gives me a little warning at the end...burps once then quits. HH%% Thanks!!!
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I have always had good luck (as has been said) with the rear of the tank shimmed out 1/8 inch and the end of the clunk turned down to a longer taper. On most of my airplanes the cutoff is so clean it's scary, no warning what so ever. On the new ship I had to go to a 6 ounce tank which just bairly fits inside the fuselage and doesn't allow for any offset. It surges a couple times at the end of the flight but in this case I'll just have to live with it. Next generation of the Latency will have a 1/4 inch wider fuselage.
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Most of us here use custom made metal tank with the wedge shape to avoid this problem.
It is much easier to set it up inside the model and it is lighter then the plastic R/C type. Mine is working since 2006.
Martin
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What RPM are you using ? Some times if you are on the rich side, at the end of the tank it will go lean and cut in and out.
Willis
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I would suggest using more Nitro. It will increase your fuel burn and make slight errors in fuel load less critical, so less chance for over-runs. I also wouldn't add castor oil, but would try some of Randy Smith's "Aero 1" additive. The increased fuel consumption will require the NV to be opened more, and that might make some difference in the shutoff. On the other hand, it will be tougher on the paint...which is one of the reasons I'm not that keen on 4S engines. D>K Steve