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Engine basics => Engine set up tips => Topic started by: frank mccune on September 09, 2016, 07:36:01 AM
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Hello:
The last time that I flew my Twister I had a severe problem with what was described as detonation.
It went like this. When the engine went from a rich 4 cycle mode to a rich 2 cycle mode, the engine ran very erratically with a lot of noise and a drop in power I adjusted the engine to a 4 cycle to where it would break into a rich 2 cycle when the nose was pointed up. This appears to be a good starting point for all of my engines. After a flight, I would make final adjustments to what suited my flying style. It was not the crackle of an overly lean mixture but a loud misfiring like I had never heard before when flying model airplanes. A couple of people suggested that it was detonating the charge rather than burning it in a smooth way. One person suggested that the engine was running too cold and I needed a hotter plug. Another suggested that the engine was overly compressed thus the added head gasket. I have never heard of this with our glow engines.
The set up was:
Engine-HP Gold Cup .40
Prop_ 11-5 or 11-4
Fuel- 11 castor 11 synthetic 10 nitro
Temperature 88 degrees
Glow plug- Fireball Med. Yellow
Air speed- 5 seconds on 65 foot lines
Tank- 4 oz. metal uniflow
I added an extra head gasket when I returned home.
I will try different plugs at the next flying session. I have used different plugs in the past but I have not seen any change in the engine running characteristics.
Has anybody else experienced this problem ? If so, what is the cause and remedy?
Tia,
Frank McCune
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Another suggested that the engine was overly compressed thus the added head gasket. I have never heard of this with our glow engines.
For once, I suggest the head gasket approach. This used to happen sometimes on the ST46 as the very soft gasket compressed, got tightened, compressed some more, tightened, etc. At some point the clearance got a touch too small, and then it would kick-back, misfire, make loud knocking sounds, etc. Replacing it with a new stock gasket usually cured it. I have similar things in other engines, too,
Note, before anyone suggests it, lowering the nitro in these cases didn't cure it. It appeared to be a function of only the head clearance/compression ratio, nothing else.
I suggest one very thin head gasket be added, or a thicker single gasket be used. Maybe 0.003 or so, it shouldn't take very much.
Jacking heads up with handfuls of gaskets willy-nilly is a really bad trend in stunt in recent years. Most people have no idea what they are doing or what changing the compression even does or what it is used to adjust. But when you have a real problem, making a tiny change is perfectly reasonable.
Brett
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Hi Brett:
Thanks for the reply! I was thinking along the same lines,
When I removed the head, I noticed that the engine had been set up with the original copper gasket and a replacement aluminum one from another engine. I simply added one additional gasket to the two original gaskets. I will know more after the temperature drops to less than 85F. Lol
Be well,
Frank McCune
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Hello:
The last time that I flew my Twister I had a severe problem with what was described as detonation.
It went like this. When the engine went from a rich 4 cycle mode to a rich 2 cycle mode, the engine ran very erratically with a lot of noise and a drop in power I adjusted the engine to a 4 cycle to where it would break into a rich 2 cycle when the nose was pointed up. This appears to be a good starting point for all of my engines. After a flight, I would make final adjustments to what suited my flying style. It was not the crackle of an overly lean mixture but a loud misfiring like I had never heard before when flying model airplanes. A couple of people suggested that it was detonating the charge rather than burning it in a smooth way. One person suggested that the engine was running too cold and I needed a hotter plug. Another suggested that the engine was overly compressed thus the added head gasket. I have never heard of this with our glow engines.
The set up was:
Engine-HP Gold Cup .40
Prop_ 11-5 or 11-4
Fuel- 11 castor 11 synthetic 10 nitro
Temperature 88 degrees
Glow plug- Fireball Med. Yellow
Air speed- 5 seconds on 65 foot lines
Tank- 4 oz. metal uniflow
I added an extra head gasket when I returned home.
I will try different plugs at the next flying session. I have used different plugs in the past but I have not seen any change in the engine running characteristics.
Has anybody else experienced this problem ? If so, what is the cause and remedy?
Tia,
Frank McCune
Need more info on the motor, it is a new or rebuild?
If it has a tight ring and chromed sleeve, that is normal, it will run very ratty until it is broken in
If it is an engine that has ran good before but not now, it could be the fuel if new
I doubt it is the CR as they run well with one al gasket, and should be no problem with the 2 head shims you said are in it
If the plug is too hot..which i seriously doubt, you can cool it down with a extra plug gasket
If it is running too hot you can add nitro and cool it down, by running richer
what about fuel is it new old ???
new glow plug? old plug?
There are many many more factors.. need more info on the engine
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Hello Randy thanks for the reply.
Here are a few answers to your questions:
The engine was rebuilt with new bearings and ring.
The engine has run great in the past.
The fuel was a commercial mix that had 10% nitro and 16% 50-50 synthetic and castor oil added. I added 6 oz of castor to this mix to get the total oil content to 22%. Perhaps this is not enough oil. I did not think that 6oz would bring the oil to 22% but the information came from a site in the internet. It must be true. Lol It seems to me that one needs 1.28 oz to equal 1 percent of a gallon. This would come out to 7.68 oz. additional oil to equal a 6% gain if one removed 7.68 oz. of exiting fuel prior to adding the oil. Is my logic flawed? The fuel was "new." Perhaps the fuel did NOT have good or enough ingredients when purchased. This is why I prefer to mix my own!
The glow plug is a new Fireball med. hot with the yellow seal.
The engine has always been a one flip starter.
I have run this fuel in another HP Gold Head .40 and it performed very well. I may use this fuel in other engines for a test. This mix is reserved for the HP engines. My other fuel mix is 10% nitro. and 28% oil that is 50/50 synthetic and castor. I use this fuel in my OS .35S and.40S engines. When I run my Fox engines .35 Stunt and .40 Stunt, I use a mix of 28% castor oil and 10% nitro. I hope that the fuels are fine for their intended uses.
In the future, I am going to try to mix only one fuel for all of my engines needs. Suggestions?
Tia,
Frank
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Hello Randy thanks for the reply.
Here are a few answers to your questions:
The engine was rebuilt with new bearings and ring.
The engine has run great in the past.
The fuel was a commercial mix that had 10% nitro and 16% 50-50 synthetic and castor oil added. I added 6 oz of castor to this mix to get the total oil content to 22%. Perhaps this is not enough oil. I did not think that 6oz would bring the oil to 22% but the information came from a site in the internet. It must be true. Lol It seems to me that one needs 1.28 oz to equal 1 percent of a gallon. This would come out to 7.68 oz. additional oil to equal a 6% gain if one removed 7.68 oz. of exiting fuel prior to adding the oil. Is my logic flawed? The fuel was "new." Perhaps the fuel did NOT have good or enough ingredients when purchased. This is why I prefer to mix my own!
The glow plug is a new Fireball med. hot with the yellow seal.
The engine has always been a one flip starter.
I have run this fuel in another HP Gold Head .40 and it performed very well. I may use this fuel in other engines for a test. This mix is reserved for the HP engines. My other fuel mix is 10% nitro. and 28% oil that is 50/50 synthetic and castor. I use this fuel in my OS .35S and.40S engines. When I run my Fox engines .35 Stunt and .40 Stunt, I use a mix of 28% castor oil and 10% nitro. I hope that the fuels are fine for their intended uses.
In the future, I am going to try to mix only one fuel for all of my engines needs. Suggestions?
Tia,
Frank
You say the engine has ran very well, if that is the case something else has changed, and the engine is not at fault look at fuel or loose parts, or glow plug
In running a HP in 4/2 you will need a HOT Glow plug ones to use are:
Glow Devil #300
T Bolt RC Long
SIG RC Long
T Bolt Big BOre
Enya 3
Merlin 2004
The HP 40 will sound a little ratty if the engine is not broken in, But since you say it ran great in the past this would not apply
The added oil did not bring it to 22% you would need to add as you said about 7.5 ounces, you have just about 20% oil "IF" you can believe the fuel you bought, if it was 16% oil by weight then NO you do not have even 20% , many fuel companies measure by weight
If your FOX 35s are in good shape and not burned Gummed up with castor they will last a lot longer with synthetic/castor blend at 28% 1/2 and 1/2. All castor fuel will shorten the life of the FOX or most any engine
Randy
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Hello Randy et al:
Thanks for the replies!
I try to support the LHS but with fuel, but I am hesitant to take the chance. A friend of mine was purchasing fuel from the LHS and when I looked at the two gallons of fuel that he was using, I was shocked to read that one gallon contained 14% oil and the other only 12%!!! My friend liked it due to the fact that it was "easier to clean off of the airplane."
I do have some Thunderbolt RC long idle bar plugs here to try but I am leery of using the fuel as it is. I will sleep better if I bring the oil content up to at least 22%.
I am willing to bet that the FUEL is garbage! No need to use it as it is as the engine is telling me that it does not like it! The time has come to mix a new batch of fuel with ingredients and proportions that I know are correct!
Again, Thanks for all of the help,
Frank McCune
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12% oil fuel is for RC cars that are on and off throttle so the crankcase loads up.