Engine/fuel tank help
 

Well, I am pretty new to this hobby but i learn pretty fast. I have had a couple motors and have had problems with them. Recieved tons of help and input as to how to make one in particular work well. An Evolution .46. I can get it to run great on the ground. Hold in air shake crazily in all angles and runs good. put it in the air and dead stick. Same with another motor. I was pretty dissapointed in the Evolution motor but i am realizing that it's probably not the engines fault just my lack of knowledge. I can get it tuned and very pleased with ground performance but I believe my fuel tanks are to blame? The models in question are the Hangar-9 P-51 PTS and the Nexstar ARF. More noticable in the nexstar than the P-51. I Crashed the P-51 and am in the process of rebuilding it so I descided to use the fuel tank to test run a new JBA motor I purchased. After pulling it out i realized that the tank is in need of a new seal or something. I fill it with gas and it only gets about half full and when I remove the fuel pump line. Wow lots of pressure and it all blows back out or pushes out the muffler. Is this because the vent is stuck? Probably due to my crash in the trees or sitting around dry? So I pulled the tank out of the nexstar and realized that it was very very loose in its fixed position. So my question is, could the tanks be vibrating, causing an irregular flow which results in deadsticks? I see clearly how to fix this issue on the P-51 as it is very easy to get to. Now on the Nexstar I have a good idea of how i would like to put in an extra bracket and foam to tighten down the tank but if someone had a pict or idea of a fix for this I would greatly appreciate. Also can someone point me into the direction "Thread" about converting Nexstar to a tail dragger.

I in advance, Thank you for your help.

[AKA]StraferX

RE: Engine/fuel tank help
 

vibration can cause problems. Sources are unbalanced props or spinners (especially if plastic or pot metal).
Tank problems can be kinks in the brass tubes or tubing, holes in the fuel lines, pinched fuel lines, etc. One problem is that the clunk inside the fuel line is connected by a short piece of fuel line and that line may grow with exposure to the fuel. So it is possible that the clunk is being blocked at times by the back of the tank. It should be about 1/4" short of touching the back end of the tank when it is made.

RE: Engine/fuel tank help
 

remember this....a fuel tank is never empty. It's either full of fuel or full of air or a mixutre of the two. When you put fuel in, air must be vented out. If fuel is blowing back out the fill line then the vent (going to the muffler is clogged). Or you are filling from the vent line. Fuel coming out the muffler means a full tank.
When filling the tank disconnect both lines and fill until fuel squirts out the vent. fill from the line that goes to the needle valve. You cannot fill from the line that goes to the muffler, or you get the result you described.
When the tank is installed make sure you have no kinked fuel lines,
Yes a loose fuel tank will cause dead sticks. I have an Ultimate Bipe after coming out of a series of snap rolls the engine died, brought her in and everything seemed ok on the ground. next flight she dead stick again at some point.. took her home and found the stick that held in the aft tank plate had come loose letting the fuel tank slide around..glued in a beefer stick on more problems

RE: Engine/fuel tank help
 

You mentioned the Evolution 46 on a Mustang PTS. Was that the RTF Version?

One of the problems with this model that the factory has not yet fixed is the cutout in the cowl for the engine. The cowl hits the low speed mixture limiter when you throttle up. This causes the low speed idle to be set to its full rich limit when you go to full throttle. You don't notice it the first time you throttle up, but the next time the engine sputters and may deadstick.

Solution: either cut the cowl to prevent the interference or remove the low speed mixture limiter. then you can get the engine properly tuned.

Brad

RE: Engine/fuel tank help
 

YEs BKdavy, that is the rtf version of the PTS p-51 I have a tank from an nexstar in it which has a seperate fill line. I had disconected the vent tube to muffler but not to the motor. Also I have removed both limiters as they didn't allow for proper adjustment.

RE: Engine/fuel tank help
 

You're running too lean . Yes..tune it on the ground.
But you have to compensate your tunning for flight. Richen it up a bit. (on the high speen needle)

that's why youre dead sticking on both engines.


If you tuned your engine from the previouse day in the afternoon when it was warmer.

Then you went out to fly the next morning persay. You'll be too lean if you don't compensate....in the morning when it's cooler
or the the air is more dense.

Also try sealing the engines backplate.
some engines are like that..that's all they need is just to be seal better.
Air being suck in through the backplate will cuase you to run lean and the engine will get hotter faster then cut out.

If both of your engines are fairly new, maybe they just need to be break in a little bit more.


prop size will also effect it..try going to a larger diameter, smaller pitch . On .46....12x4 is an odd ball size but it'll give
you torque like a 4 stroke.

RE: Engine/fuel tank help
 

Lean yes...

The PTS also has a couple of basic problems... you are experiencing one.


The low end needle will "walk" as you advance and retard the throttle causing the tuning to change in flight. This is more pronounced once the engine warms up.


I've seen this with every PTS P-51 I've owned ( three ) and with those brought by others out to our field ( five ).

My first solution to this was to insert a cut piece of an exhaust deflector tube, to fit over the LS needle and hold the clip against the detents. It helped a LOT.

Later I resorted to removing the needle, bending the clip in so it exherts more force, and with a micro-brush applying a micro-drop of BLUE Lock-tite on the LS needle threads. You must be careful NOT to get lock-tite anywhere else, and you must clean the threads on the needle and receptacle before you do this...

I do this to everyone who asks for help with their PTS, and the problems seem to mysteriously vanish.

The HS needle is also prone to movement, so bending the clip is also advisable.