hebrew15
08.06.2021 9:51:11
TIPS FOR SUCCESS [links]
See full version: Optimize Your Fuel System For Best Performance
TIPS FOR SUCCESS [links]
The first type Im sure everyone has seen. Its used on almost every ARF airplane and is shown in the instructions included with fuel tanks from nearly every supplier. I call it the conventional tank system. It usually has two lines: The feed or pickup line and the vent/overflow/pressure line. The feed line attaches to a weighted fuel pickup inside the tank called the clunk. This line connects to the carburetor inlet and feeds the engine with fuel. The clunk assures that the pickup is always submerged in fuel regardless of the airplanes attitude. The second line is a rigid piece of tubing (usually brass or aluminum) and it runs to the top of the tank (when the airplane is sitting upright). It attaches to the muffler pressure line or it may simply be left open, exposed to the atmosphere. As long as air may enter the vent line, fuel shall be allowed to flow out of the feed line. It is important to understand this principle, otherwise youll have a hard time understanding how the fuel system works. To fill the tank with fuel, you remove the feed line from the carburetor and pump fuel into the tank until it runs out of the overflow line. To empty the tank, you pump fuel out of the feed line. Air enters the tank through the vent line because it is exposed to the atmosphere. If it didnt, you wouldnt be able to pump the fuel out because youd start to create a vacuum in the tank.
Now what is the third line for? Well, what did we forget? Thats right, the muffler pressure line. Heres where it gets complicated. You can of course just connect the line directly to the muffler. If the muffler or carburetor is easily accessible, that might work. Keep in mind you need to remove either the carburetor/ feed line or the muffler/pressure line to fill or drain the tank. I also like to install a check valve in the muffler line to improve the effectiveness of the muffler pressure and to eliminate the possibility of fuel entering the muffler under certain flight conditions.
The fuel system is one of the most important parts of your airplane, but how much do you really know about it? Do you understand the theory behind how it works? Did you know that there are several different types of fuel system architectures and do you know which one is best for your specific application? The more you understand about this part of your airplane, the better off youll be. We are going to look at the glow engine fuel system in detail. A lot of this may apply to gas powered models as well, but in all fairness they should be discussed separately. Alright, class is in session. There wont be a test until you get to the field next weekend!
The rigid line that goes to the top of the tank is no longer going to be a vent/pressure line. It will only be used during refueling as the overflow line. Since it goes to the top of the tank, it will let you know when the tank is full because fuel will run out. Once youre finished filling the tank, you need to plug this line. Very important! You can use a plug or a fuel dot.
So whats the best choice for your airplane? Hopefully now you have enough knowledge to make that decision on your own. The best advice I can give would be to make sure you understand everything discussed thus far. If you dont have confidence in something, then by all means dont use it. If youre still undecided here are a few simple guidelines: [links]
1. I've seen some fuel setups with 2 lines. I can't see how these work- or what am I doing wrong. When you fill the tank there is no air vent and the fuel floods the engine. e.g. air in the tank pushes the fuel into the carb, It has no other place to go. Seems like a 3 line is a must for gasoline engines?
Depends on the location of the carburetor and if you can access the opening of the carburetor to use the fuel bulb. If you think you can do it then why not. Go ahead and knock yourself out. However for most other people flipping the prop is a good way to prime the engine. The reason is that the Walbro carburetor has a pump. When you flip the engine the pump will prime and the fuel will get into the carburetor. Some Walbro carburetors also comes with a primer bulb you can squeeze to prime the carburetor. Some Walbro also has a choke. So to answer your question there are many ways to prime the engine. Your way is only ONE of the ways. Open your mind to other possibilities before jumping to conclusion.
>>1. I've seen some fuel setups with 2 lines. I can't see how these work- or what am I doing wrong. When you fill the tank there is no air vent and the fuel floods the engine. e.g. air in the tank pushes the fuel into the carb, It has no other place to go. Seems like a 3 line is a must for gasoline engines?<< more
Perry is the manufacturer for high quality carburetors, pumps, and fuel management systems for both OEM and aftermarket use in model aviation, boats, and cars.
New Braunfels, Texas 78130
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Properly installed, your fuel system will last a very long time and may never need to be changed. In a hard landing, however, some of its parts may be dislodged or a line can become kinked or pinched. Here are some common fuel-flow problems and fixes.
One common problem that can lead to your engine running lean is fuel foaming in the tank. Vibration causes this and it forms tiny bubbles in the fuel. The bubbles cause erratic fuel flow and the air in the bubbles causes the fuel mixture to lean out! The simple solution to this is to make sure to properly pad your fuel tank with soft foam rubber. Also, make sure that after time you check the padding to see if any part of the unprotected tank is coming in contact with the model’s inner structure like a former or engine mount bolt or nut. I prefer to use rubber bands to hold the foam padding in place but you can also use tape. Make sure you don’t compress the foam too much as this will lessen its ability to isolate the tank from the vibration.
To fill a gasoline tank you can add a T-fitting to the engine’s fuel supply line with an added length of tubing. When you pump fuel into this line, it only flows into the tank and won’t flood the engine. When the tank is full, plug the fill line and the engine draws fuel from the tank. By adding a long fill line and using a Fuel Dot, you can place your “filler cap” anywhere you like, this is great for scale models with large fiberglass cowls that hinder easy access to the fuel lines.
A two-line fuel system is the simplest and almost foolproof way to go. The setup requires only two pieces of brass tube, a clunk, a rubber stopper and a short length of silicone tubing. Bend one tube 90-degrees to form the vent and insert it through the stopper. The vent lets outside air in as the fuel is drained out, and it acts as an overflow indicator when you fill the tank. The second tube is the fuel-supply for the engine and the interior pick-up tube and clunk are attached to it. To fill the tank, the fuel supply tubing is removed from the carburetor and attached to your filler pump line. When the tank is full, you simply reattach the line to your carburetor. The vent line is often attached to a pressure fitting on the engine’s muffler. This arrangement helps pressurize the tank to enhance fuel flow to the engine. here
Lengths of brass tube pass through the tank’s rubber stopper, and the fuel lines that carry the fuel to the engine slip over the ends brass tubes. The rest of the fittings and accessories help the fuel system work properly and make it easier to maintain and operate.
T-Fittings are usually used with 2-line fuel tank setups for gas engines. Installed between the Carb and the tank. This makes refueling without disconnecting the line from the carb possible because the pumper Walbro carb does not flood when the fuel is pumped in.