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G-26 ZENOAH, FLAMES OUT

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Old 11-02-2012, 02:12 PM
  #1
aframe2
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Default G-26 ZENOAH, FLAMES OUT

I have a Zenoah G-26 that seems to have an afraid of height phobia. This engine will run
great on the ground. It will purr like a kitten at idle all day long. When I rev it up to maximum
rpm's it runs like a champ. When I taxi it out to the flight line, take off; do a couple of loops
around the field, it will flame out. Sometimes it seems like it is loosing power, power gets less
and less and then it just flames out. Other times it will be running fine in the air, and all of a
sudden just like the gas was gone from every orifice of the motor. I changed all of the gas lines
from the tank to the carb a couple of times, so I don't think I have a fuel line problem. I put a
nipple on the carb diaphragm and ran fuel line back into the fuselage for that static pressure solution
and it seems to run fine with that fix. I have a 16x8 prop. I have all winter to figure it out, would like
some constructive criticism on what to do next. Thanks, Aframe2
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Old 11-02-2012, 02:30 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

Sounds as though you have already found the solution to your leaning out problem?
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Old 11-02-2012, 02:36 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

Aside from a constant carb reference pressure, maybe also turn your attention to engine cooling?
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Old 11-02-2012, 04:01 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

When you hear it sagging out in the sir, land it and re-adjust your needles.
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Old 11-03-2012, 06:45 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

PS
That pill bottle is for what? Just make a decent static port!
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Old 11-03-2012, 07:08 AM
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aframe2
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Default RE: G-26 ZENOAH, FLAMES OUT

Pe reivers, I saw somewhere on RCU that people were using either an old film canister, or a pill bottle to run
the line from the static port. I assumed it was to keep a lot of exhaust dirt or whatever comes out of that
line from fouling up the inside of the fuse. Wasn't my idea, but if you think I should take it out, I will try it.
One more thing I was observing when another member mentioned overheating. I have a pitts style wrap
around muffler that might be blocking the air dam that is at the rear of the engine. I will try and upload a
picture to show what I am talking about. Do you think this might be blocking air from escaping and causing
the engine to overheat, and if it is the culprit, how do I fix it? Thanks, Aframe2
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Old 11-03-2012, 07:12 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

By the pics you posted, I would highly suspect overheating. There sure isn't much in the way of exit cooling there.
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Old 11-03-2012, 07:15 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

Pe reivers, is that hole on the outside of your fuselage the end
of the fuel line coming from your static port? I have to have things
spelled out for me, sorry. So you are saying just run the line back
and exit somewhere out of the fuselage? Does it make a difference
how long that line is? Thanks, Aframe2
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Old 11-03-2012, 07:18 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

K-Bob, i'm inclined to agree with you, but given the way this is set up, what
do you think the solution to remedy the situation is? Aframe2
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Old 11-03-2012, 07:40 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

The pill bottle must be open.

The vent line must be allowed to breath in and out.

There is no fuel that comes out of it unless the diaphragm is blown which never happens. The diaphragms just get stiff.

You have your exit air almost completely blocked off by the muffler! Your engine is overheating!

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Old 11-03-2012, 07:56 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

OK, my two cents.

First the static port. It is connected to the carb regulating diaphragm chamber. The line can be long, and must terminate on the outside of the fuselage in a smooth fashion. Not prone, nor sunken. The fuselage section must be straight, not curved lengthwise. That way the carb get exactly outside air pressure for reference.

About the cooling.
There is not much of an air exit. The one real effective exit, the trailing end of the cowling standing slightly prone from the fuselage, is blocked by that nice seal you put in there. Make a couple of standoffs to define the air exit slit of about 1/4", and remove the seal.
Then place a baffle in front of the engine do direct all airflow over the cooling fins.

Lastly:
Your ignition HT wire rubs on the muffler. It will wear, but most of all get too hot locally, causing deterioration of the HT insulation. That is an ignition failure waiting to happen.
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Old 11-03-2012, 09:46 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

W8ye and Pe, thanks for your advice. I will correct all of those things you suggest
and will let you know if the engine runs better after that. Thanks, very constructive
criticism. Thanks again, Aframe2
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Old 11-03-2012, 09:52 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

you're welcome.
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Old 11-03-2012, 01:15 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

I don't have a solution; only to say I have G26 that behaves in the same manner, but it is intermittent. The engine is mounted out in the open on the nose of giant ugly stik. Sometimes adjusting the carb works and then again it does not help. At other times when the situation occurs, an engine restart will cure the problem for a few flights and then we go back to square one. Replaced the carb and it did not help. Go figure.[:@]
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Old 11-03-2012, 01:49 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

I will offer my persoanl experience and also agree with PE on the answers he submitted to you.

1st thing I would like to add is to ensure your vent tube is not restricted to your tank. I had mine melt close when it got to close to the muffler and the engine went lean and died.

2nd is. You have got to get the exit open on that cowl. Either dremel it open or buy screens and paint over them on the bottom. General rule of thumb is, they need to be about 50% bigger than your inlets. This will cause a venturi effect and allow the engine more cooling.

Reroute your spark plug wire where it is not metal to metal.

Since you have already "normalized" your carb the engine should not be so tempermental in the air.

My synopsis is that your engine is overheating and dying in the air.

bottom line is more air flow.

My 2 cents worth.

Wish you the best

Glenn Williams
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Old 11-03-2012, 02:02 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

Heat........ You are running hot when it loads up. Same as above recommendations, open up the cowl and let some air move. You can have the best baffeling possible, but it does no good if the HOT air can not get out. With the wrap around pitts, you are just compounding the issue.

Cheers
Derrick
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Old 11-03-2012, 02:22 PM
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aframe2
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Default RE: G-26 ZENOAH, FLAMES OUT

Thanks, guys, I hope it is a overheating problem. I think I can fix that situation. This is the plane
that the engine is on. It is a beautiful model. I just hope I can get the engine to run correctly,
so I can get some enjoyment out of flying the model. Aframe2
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Old 11-03-2012, 02:43 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

Hi, I wouldn't take it that lightly for overheating an engine to the point of rpms dropping off will surely effect the overall health of the motor, I would much rather find a tiny blade of grass in the spraybar.
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Old 11-03-2012, 04:13 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

aframe2,

Are you using a fueler valve? They are notorious for sucking air. Usually ok at an idle, but later when more power is needed, flame out or lean out. Just an idea.

Darrolair
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Old 11-03-2012, 04:48 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

If you enlarge the exits and kick out exit ports on the cowl it will increase the airflow. The portion of the cowl that makes the angle out creates low pressure. You could make them with triangle stock. Also putting baffeling to direct the air toward the head is very beneficial.
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Old 11-03-2012, 05:40 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

1. Sounds like over heating. Try flying without the cowl. Make sure to compensate for the cowl weight on CG. Then if no issues you need to open up the cowl bottom, especially as mufflers get really pretty hot and air can circulate in the cowl. Temp gun could check cylinder head temp below 180-185 F.

2. Also check you carb standoff block for any cracks . Sound a lot like mY friends zenoah. Exhibited same perfect on the ground then poor in the air. Had a crack in the block. I never would have caught it as it was cracked on the underneith side.

Good luck.
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Old 11-04-2012, 02:47 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

FireBee, ok I will also check that block for cracks. Thanks again RCU for a wealth of advice
that I would have never have caught on my own. Aframe2
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Old 11-05-2012, 02:46 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

Aframe2,

Sometimes in order to reach the proper exit/intake air ratio (I shoot for 3-5:1) without totally destroying your entire cowl it is best to actually restrict the intake air into the front of the cowl so that all of the intake air is directed at the cylinder and nowhere else. This is especially important with radial style cowls where you have a huge intake area.

From your posted photos I can't tell if you have a dummy radial in the cowl or if it is wide open. I would think a well thought out front baffle that directs air to the cylinder and then open the exit air around the muffler to the proper ratio and your engine should run much more reliably.

If your engine seesm down on power after doing all this you may have damaged the rings by the previous episodes of overheating. But that is a pretty easy fix to replace them and you should be back to an almost brand new engine with great power.

Cheers,

Pete
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Old 11-06-2012, 03:04 AM
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Default RE: G-26 ZENOAH, FLAMES OUT

The cowl need not be opened. See post 20. The ring shaped air exit is extremely effective, especially if the incoming air area is restricted to engine front entry only. A ratio of 1:1.2 will be perfect if pressure difference between air intake (ram air) and air exit (suction) is good.
I often get away with a ratio of mere 1:0.8 by forcing all cooling air through the engine fins.
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Old 11-07-2012, 12:54 PM
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Default RE: G-26 ZENOAH, FLAMES OUT

Pe, and others, this is the front of the cowl with the dummy
engine. I have a big air opening directly in front of the engine
fins, and three other small access holes around the dummy engine
for screw access. Aframe2
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