O&S .61 FX burning out glow plugs
07-21-2014, 07:34 AM
#26
Join Date: Dec 2001
Location: Upplands Vasby, SWEDEN
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Hi!
Some advise!
1. Use OS 8 or ENYA 3 glow plugs (Idle bar plugs are not as good or reliable in modern engines)
2. Use 5-15% nitro fuel !
3. See to that the tank is not to big, 12-16oz is fine.
4. See to that the tank is mounted correctly (with the center in line with the fuel intake orifice in the carb when the plane sits horisontaly). Mounted in lots of SIG-foam!
5. Use the best tank set-up possible! This means using either a Tettra "Bubbleless"tank or using ordinary tank set-up with Uni-flow system (Two clunks,one going to the carb the other going to the pressure line). An ordinary 2-line fuel tank is not as good!
5. Use an APC ,RAM or Graupner Cam-prop or G-Sonic prop. Master A is no good performance or sound vise!
6.Balance the props and spinner!
7. Have adequate cooling air to the engine...and bigger outlet! And direct the incoming air around the cylinder fins! Just making a hole up front is not enough!
8. Don't set the engine lean!
Hold the nose of the plane straight up when you set the engine, and set it slightly rich!
Some advise!
1. Use OS 8 or ENYA 3 glow plugs (Idle bar plugs are not as good or reliable in modern engines)
2. Use 5-15% nitro fuel !
3. See to that the tank is not to big, 12-16oz is fine.
4. See to that the tank is mounted correctly (with the center in line with the fuel intake orifice in the carb when the plane sits horisontaly). Mounted in lots of SIG-foam!
5. Use the best tank set-up possible! This means using either a Tettra "Bubbleless"tank or using ordinary tank set-up with Uni-flow system (Two clunks,one going to the carb the other going to the pressure line). An ordinary 2-line fuel tank is not as good!
5. Use an APC ,RAM or Graupner Cam-prop or G-Sonic prop. Master A is no good performance or sound vise!
6.Balance the props and spinner!
7. Have adequate cooling air to the engine...and bigger outlet! And direct the incoming air around the cylinder fins! Just making a hole up front is not enough!
8. Don't set the engine lean!
Hold the nose of the plane straight up when you set the engine, and set it slightly rich!
Last edited by jaka; 07-21-2014 at 08:23 AM.
07-21-2014, 03:10 PM
#29
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If you can open it up to four turns, I suspect an air leak along with other problems. It sounds like you really do not have control over the fuel flow. I suspect you get plenty of fuel because the tank is to high. When it burns down to where it is even with or slightly below the carb, you need a bit of assistance to move the fuel to support the high airflow carbs. That is a tank pressure feed. So when you get to the half tank point or near it, the engine goes lean and quits - because it is not getting fuel.
The four turns sort of indicates to me an air leak, air leaks around the carb throat or a loose back plate sucking in air. That will allow an over rich setting to allow an almost normal operation for a while. So there are more than one problem facing you. I agree the pooling of fuel can lead to plug failure. But not sure how the fuel gets there if the engine goes lean and dies.
OS engines like short plugs, at least most of the OS plugs are short. So I would go for the short plug. Or go for the type F OS plug, while long has a longer filament and may last longer. Don't understand why the use of the old style plug, yes they work but are not usually need on modern engines.
Regardless, I am still concerned that you can open the high speed needle up to four turns and still get normal high RPM. And yet you do so. Do you have a on board glow driver firing the plug? The home built wrap around muffler maybe heating up the engine. You will need an extraordinary amount of cooling for the engine. Remember you need twice as much cooling exhaust area as the intake area for cooling. Just having air big intake cools nothing, it is the path through the cowling that must provide the cooling. So if you do not have a sufficient path for the air to enter and exit, you gonna get extra heating. So your engine may be stopping due to over heating not a lean run.
I hope those thoughts help. Not being there and seeing what is going on limits us all to guessing. Do tell us what is the final fix.
The four turns sort of indicates to me an air leak, air leaks around the carb throat or a loose back plate sucking in air. That will allow an over rich setting to allow an almost normal operation for a while. So there are more than one problem facing you. I agree the pooling of fuel can lead to plug failure. But not sure how the fuel gets there if the engine goes lean and dies.
OS engines like short plugs, at least most of the OS plugs are short. So I would go for the short plug. Or go for the type F OS plug, while long has a longer filament and may last longer. Don't understand why the use of the old style plug, yes they work but are not usually need on modern engines.
Regardless, I am still concerned that you can open the high speed needle up to four turns and still get normal high RPM. And yet you do so. Do you have a on board glow driver firing the plug? The home built wrap around muffler maybe heating up the engine. You will need an extraordinary amount of cooling for the engine. Remember you need twice as much cooling exhaust area as the intake area for cooling. Just having air big intake cools nothing, it is the path through the cowling that must provide the cooling. So if you do not have a sufficient path for the air to enter and exit, you gonna get extra heating. So your engine may be stopping due to over heating not a lean run.
I hope those thoughts help. Not being there and seeing what is going on limits us all to guessing. Do tell us what is the final fix.
07-22-2014, 10:33 AM
#31
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I took his statement to mean little back pressure to the engine exhaust, not pressure to his tank. He indicated it was a homemade muffler and made no mention of a pressure tap for his tank. I will admit low back pressure will effect an ABC/ABN engine and increasing the back pressure would indeed help the engine. But he seems to have no problems with his high RPM, does not say much about cowling/cooling issues, and seems to have a tank higher than his engine. He has multiple issues.
Still would like to know if he cures his problems.
Still would like to know if he cures his problems.
07-22-2014, 12:34 PM
#32
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I took his statement to mean little back pressure to the engine exhaust, not pressure to his tank. He indicated it was a homemade muffler and made no mention of a pressure tap for his tank. I will admit low back pressure will effect an ABC/ABN engine and increasing the back pressure would indeed help the engine. But he seems to have no problems with his high RPM, does not say much about cowling/cooling issues, and seems to have a tank higher than his engine. He has multiple issues.
Still would like to know if he cures his problems.
Still would like to know if he cures his problems.
Thanks men for all the advice. Problem solved. Hemikiller nailed the problem. Not enough back pressure on my home made muffler. I blocked off one of the tubes, and voila runs like a clock. Just starved for fuel. No wonder it was turning 11000 rpm! What kind of tipped me off also, was the Pitts for my .91. Taking a look at them together, I could tell my home built had a lot more volume then the Pitts, and larger exit tubes. Blocked one tube off and good to go. Thanks all...
