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Model Forum / Radio Controlled / Air Models / May 2004Fuel draw distance
What is a typical distance (from carb to fuel tank) that fuel draw will be ok on a .76 sized two-stroke engine with muffler pressure? I have a GMS 76 engine and need an estimate as to how far back a tank can be mounted and still get proper fuel draw. I know there are a lot of variables. Thanks. John VB With just exhaust pressure, I would avoid anything over about 6-8 inches. There is no reason it wouldn't draw farther than that but you would start running into draw problems during takeoff and vertical flight. -- Paul McIntosh http://www.rc-bearings.com > What is a typical distance (from carb to fuel tank) that fuel draw will be > ok on a .76 sized two-stroke engine with muffler pressure? I have a GMS 76 > engine and need an estimate as to how far back a tank can be mounted and > still get proper fuel draw. I know there are a lot of variables. Thanks. > > John VB >http://www.rc-bearings.com >> What is a typical distance (from carb to fuel tank) that fuel draw will [quoted text clipped - 5 lines] >> >> John VB >With just exhaust pressure, I would avoid anything over about 6-8 inches. >There is no reason it wouldn't draw farther than that but you would start >running into draw problems during takeoff and vertical flight. > >-- >Paul McIntosh Problem with friction in the fuel line can be adjusted with richer mix, but Paul is right about takeoff and vertical ~ Putting the tank a foot behind the motor, fuel must be pulled upwards, against gravity ~ it'll go WAY too lean. The engine and its fuel are friends; keep 'em close. DC3 Thanks Paul. The back of my tank is 11 inches from the carb. I have been having problems with the engine quitting in vertical maneuvers when the fuel is getting low. I suspected that my tank was too far back. I am using a Hayes slimline (long and skinny) tank. Probably need to use a short, fat tank. The front of the tank is against the firewall. Anything else I can do other than put on a kline regulator? John VB > With just exhaust pressure, I would avoid anything over about 6-8 inches. > There is no reason it wouldn't draw farther than that but you would start [quoted text clipped - 11 lines] > > > > John VB Not really. Gravity and inertia are against you. -- Paul McIntosh http://www.rc-bearings.com > Thanks Paul. The back of my tank is 11 inches from the carb. I have been > having problems with the engine quitting in vertical maneuvers when the fuel [quoted text clipped - 21 lines] > > > > > > John VB Perry/Varsane regulating pump. I have used them to put the fuel tank on the CG with over 12 inches of fuel line from the tank output.  SignatureDumpster | Thanks Paul. The back of my tank is 11 inches from the carb. I have been | having problems with the engine quitting in vertical maneuvers when the fuel [quoted text clipped - 21 lines] | > > | > > John VB > What is a typical distance (from carb to fuel tank) that fuel draw will be > ok on a .76 sized two-stroke engine with muffler pressure? I have a GMS 76 > engine and need an estimate as to how far back a tank can be mounted and > still get proper fuel draw. I know there are a lot of variables. Thanks. > > John VB Try a pump! Might even combine it with a small header tank close to the engine if you have the room. With a pump you can probably hang a tank just about anywhere. Chuck FWIW, I put two tanks in an airplane with a .46pro and the tanks were in series, one feeding the other. Had to do this to get it to balance. The back tank was just under the CG maybe about 12 inches from the carb. No pump. Seemed to work just fine. It was an early Pilatus Porter. Fun plane to fly. I think I used large diameter fuel line. > What is a typical distance (from carb to fuel tank) that fuel draw will be > ok on a .76 sized two-stroke engine with muffler pressure? I have a GMS 76 > engine and need an estimate as to how far back a tank can be mounted and > still get proper fuel draw. I know there are a lot of variables. Thanks. > > John VB |
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