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Model Forum / Radio Controlled / Water Models / November 2005what is the differance between 16% and 25% nitro fuel??
what is the differance between 16% and 25% nitro fuel?? apart from the 25% being more combustable which has the better lubricating quality?? > what is the differance between 16% and 25% nitro fuel?? 25% is more expensive. > apart from the 25% being more combustable which has the better lubricating > quality?? The one with more oil :-) Nitro does not lube an engine. The combustible bit is methanol. The 25% will run the engine harder, faster, possibly cooler, give more power. The 16% is likely to be indistinguishable from the 25% unless you fly like the dogs danglies and need to push your 90 sized 3D chopper thru this years 3D Masters. If you have to ask, you dont need 25% nitro. Actually, you likely dont need 16% either. D > what is the differance between 16% and 25% nitro fuel?? > apart from the 25% being more combustable which has the better lubricating > quality?? > Nitro does not lube an engine. > [quoted text clipped - 9 lines] > If you have to ask, you dont need 25% nitro. Actually, you likely dont need > 16% either. so you recommend the 20% then/?? > D > > what is the differance between 16% and 25% nitro fuel?? > > apart from the 25% being more combustable which has the better lubricating > > quality?? >> Nitro does not lube an engine. >> [quoted text clipped - 11 lines] > > so you recommend the 20% then/?? You need to say what you're putting it into (both engine, model and any other pertinent details) for a more helpful answer. > so you recommend the 20% then/?? Actually 0-15% is fine for most sport flying, depending on the engine. Some engines idle better with some nitro. No, it depends what you want to do with it. What are you trying to achieve? David >> Nitro does not lube an engine. >> [quoted text clipped - 20 lines] > lubricating >> > quality?? Well just for the record...I have a Classic an old COX .15 Medallion -class of 1981- an all I have ever used in it is 10% , It is currently on my 36" airboat an doing a great job , I have 1 new glowhead an 1 on the engine when they are gone guess Ill have to buy me another engine , COX does not make the .15 anymore . Some experiments I have done ::: Diesel fuel...1 pint add 1/4 cup alcohol , to raise the cetaine of the diesel , 1/4 cup 5w oil. works good in a pinch. Dont ever try an use gasoline IT will not work haha, I burnt up a plane one time with it , That was back when i was young an dumb ,,haha.. So stick with the low end stuff , if your engine works good on 10% use it . Lee About Cox 15 glow plugs. When you burn the next one out do not throw it away. You can buy a 1/4-32 tap and tap drill to thread the head for a standard glowplug. Almost any machine tool supplier can supply them or just google 1/4-32 tap. Have done it to several engines, Cox heads were too expensive. Hugh Well just for the record...I have a Classic an old COX .15 Medallion -class of 1981- an all I have ever used in it is 10% , It is currently on my 36" airboat an doing a great job , I have 1 new glowhead an 1 on the engine when they are gone guess I'll have to buy me another engine , COX does not make the .15 anymore . Some experiments I have done ::: Diesel fuel...1 pint add 1/4 cup alcohol , to raise the cetaine of the diesel , 1/4 cup 5w oil. works good in a pinch. Don't ever try an use gasoline IT will not work haha, I burnt up a plane one time with it , That was back when i was young an dumb ,,haha.. So stick with the low end stuff , if your engine works good on 10% use it . Lee (snip) About Cox 15 glow plugs. When you burn the next one out do not throw it away. You can buy a 1/4-32 tap and tap drill to thread the head for a standard glowplug. Almost any machine tool supplier can supply them or just google 1/4-32 tap. Have done it to several engines, Cox heads were too expensive. Hugh Thanks Hugh I might try that , course it might be another 10yrs before I need to try it. Lee I saw this question earlier. It was cross posted in several groups. I have some answer in this page: http://www.btorcboat.com/html/CH3NO2.html I saw many opinions too: run your engine cooler, better idling.... Both were wrong. > what is the differance between 16% and 25% nitro fuel?? 6% > apart from the 25% being more combustable which has the better lubricating > quality?? That's not right though is it? The "combustibility" of a fuel has nothing to do with it's lubricity as that's got everything to do with the lubricant. 25% nitro (an odd percentage I have to say) *may* allow an engine to run slightly cooler IF the mixture is run as rich as it can be run without interfering with the carbs function, but it's unlikely that anyone asking the question would notice the difference, because it's only when flying to the max it becomes noticable, and someone able to fly to the max would know the answer to the question, therefore making the question moot. A newbie certainly won't be able to tell the difference from a power point of view, although he *may* notice a slightly smoother idle, but who flies a heli with the engine idling? (those doing auto's all day of course, which once again rules out a newbie) In the real world, the best fuel for a newbie to use is the cheapest, because he'll be burning GALLONS of the stuff.  SignatureBeav Reply to "beavis dot original at ntlworld dot com" (with the obvious changes) > > what is the differance between 16% and 25% nitro fuel?? > > 6% fx:splutter 16 + 6 = 25? I think not, go back to school ! -- Vass >> > what is the differance between 16% and 25% nitro fuel?? >> [quoted text clipped - 3 lines] > > 16 + 6 = 25? I think not, go back to school ! And you need to keep up to speed on the NG. Check back 2 days before your post. SignatureBeav Reply to "beavis dot original at ntlworld dot com" (with the obvious changes) Approx 9% difference! > what is the differance between 16% and 25% nitro fuel?? > apart from the 25% being more combustable which has the better lubricating > quality?? > Approx 9% difference! A bit closer than my 6% :-)) Must learn to differentiate between a 6 and a 6 (9 I mean:-) SignatureBeav Reply to "beavis dot original at ntlworld dot com" (with the obvious changes) >>Approx 9% difference! > > A bit closer than my 6% :-)) > > Must learn to differentiate between a 6 and a 6 (9 I mean:-) Inverted arithmetic? >>>Approx 9% difference! >> >> A bit closer than my 6% :-)) >> >> Must learn to differentiate between a 6 and a 6 (9 I mean:-) > Inverted arithmetic? Not a bit of it, just piss poor maths :-) SignatureBeav Reply to "beavis dot original at ntlworld dot com" (with the obvious changes) >>>Approx 9% difference! >> >> A bit closer than my 6% :-)) >> >> Must learn to differentiate between a 6 and a 6 (9 I mean:-) > Inverted arithmetic? Just crap typing:) (Well that's my story:-)) SignatureBeav Reply to "beavis dot original at ntlworld dot com" (with the obvious changes) > >>>Approx 9% difference! > >> [quoted text clipped - 4 lines] > > Just crap typing:) (Well that's my story:-)) And he is sticking to it :-) > what is the differance between 16% and 25% nitro fuel?? > apart from the 25% being more combustable which has the better lubricating > quality?? Use a fuel that matches the engine maker's minimum recommendations, most say either 0% or 5%-10% minimum nitro content. Any more is just burning money unless you need ultimate performance. The oil content and type, which determines it's lubricating qualities, is an entirely separate issue. Quite why you've cross posted to so many unrelated groups is beyond me, if you want help then at least narrow it down to a boat, plane or car ! Greg > > what is the differance between 16% and 25% nitro fuel?? > > apart from the 25% being more combustable which has the better lubricating [quoted text clipped - 9 lines] > > Greg hi greg i posted to differant groups because they use two stroke engines that use nitro fuel, and i find it very interesting to read the different types of replys, thus learning about each type of hobby and a series of flight,cars,trucks,boats at the same time > > what is the differance between 16% and 25% nitro fuel?? > > apart from the 25% being more combustable which has the better lubricating [quoted text clipped - 9 lines] > > Greg Well said Greg, Personally I prefer to use straight fuel with no nitro - the engines and models I fly don't need the extra power and I rarely have idling/pick up problems. Nitro releases oxygen as it breaks down in the engine and effectively improves the "breathing" of the engine - more oxygen to combine with the methanol gives faster burn and more power. There can be a down side. There is a view that residual nitro left in an engine can lead to more corrosion than would be caused by straight fuel - methanol absorbs moisture which causes the corrosion which can be aggravated by the nitro apparently forming nitric acid when moisture is present. Fuels containing nitro are more expensive - the more nitro, the higher the cost. Only a few special engines ever need more than 10%, 5% is more than adequate for most sport flyers. Whatever fuel you use, the best way to avoid corrosion is to run the engine until it stops for lack of fuel and inject some sort of after run oil while the engine is still warm. Malcolm > > > what is the differance between 16% and 25% nitro fuel?? > > > apart from the 25% being more combustable which has the better [quoted text clipped - 21 lines] > improves the "breathing" of the engine - more oxygen to combine with the > methanol gives faster burn and more power. The oxygen from the nitro immediately bonds to the carbon in the nitro to form CO and CO2 and other compounds, it doesn't combine with methanol which bonds with its own oxygen and oxygen from the air. The extra energy is from breaking the nitrogen bond and the larger mass of the heavier fuel. > There can be a down side. There is a view that residual nitro left in an > engine can lead to more corrosion than would be caused by straight fuel - > methanol absorbs moisture which causes the corrosion which can be aggravated > by the nitro apparently forming nitric acid when moisture is present. There are lots of views, but many are not fact. Fact is that nitro is a stable compound, especially in the prescence of methanol, oil, and water. Nitric acid is a very unstable and toxic compound which will not linger very long. It is used for rocket fuel and will often ignite when in contact with many flamable substances. Nitro will not transform into a more unstable compound without energy. However nitric acid is formed from the uncomplete combustion of nitro, however unless you are running 100% nitro very little nitric acid is produced. Likely they are worried because nitro itself is a very mild acid with a Ph of around 6.8. > Fuels containing nitro are more expensive - the more nitro, the higher the > cost. Only a few special engines ever need more than 10%, 5% is more than [quoted text clipped - 5 lines] > > Malcolm > Well said Greg, > > Personally I prefer to use straight fuel with no nitro - the engines and > models I fly don't need the extra power and I rarely have idling/pick up > problems. I mainly fly OS engines which are made for 5-10% nitro so that's what i buy. > Nitro releases oxygen as it breaks down in the engine and effectively > improves the "breathing" of the engine - more oxygen to combine with the > methanol gives faster burn and more power. As I under stand it this also results in a hotter engine and earlier ignition, so with high nitro fuel it's necessary to use a cooler plug to compensate. We have no other way of altering the timing in our engines. > There can be a down side. There is a view that residual nitro left in an > engine can lead to more corrosion than would be caused by straight fuel - > methanol absorbs moisture which causes the corrosion which can be aggravated > by the nitro apparently forming nitric acid when moisture is present. Yes that's apparently the case, but the easiest way around it is to use a quality fuel that has anti-corrosion additives. > Whatever fuel you use, the best way to avoid corrosion is to run the engine > until it stops for lack of fuel and inject some sort of after run oil while > the engine is still warm. Model Technics have told me that the anti-corrosion additives in their fuel are basically the same as in their after-run oil, and consequently there is really no need to use it as there is always a good coating of oil left in the engine. though I must admit I do use after-run when storing engines. Greg > what is the differance between 16% and 25% nitro fuel?? > apart from the 25% being more combustable which has the better lubricating > quality?? 9% nitro? Straightly speaking is: higher % nitromethane give more power. More power is higher rpm and/or higher torque. It depend on the type of model you are running. Car need higher rpm. Boat and airplane do not need higher rpm but higher power, turn a larger propeller without lowering the rpm. Nitromethane is CH3NO2. It is the O2 matter the power. As nitromethane burn, will release O2, that is the source of oxidizer. So, for the same amout of air, higher nitromethane content can burn more fuel. That is why more power come. With higher % nitromethane, you need to open the needle valve more. The engine suck same amount of air, but higher volume of fuel, so give higher power. Your model will run faster, fuel will be used up faster. Nitromethane do not help ideling. Instead, you need to choose correct glow plug temperature that really matter the ideling. Nitromethane also do not help running your engine cooler. Higher power means more energy is released in the same amount of time. So, your engine will become hotter. Power is J per second. If you look at some new model of car engine, will found that the heat sink fin area in continuing increasing. Some Nove Rossi engine almost use up all area of the crank case. Lubricant do not give power but protect the engine. > what is the differance between 16% and 25% nitro fuel?? > apart from the 25% being more combustable which has the better lubricating > quality?? I will respectfully differ with you on a couple of points. 1. Higher nitro levels in four strokes SIGNIFICANTLY improve idle and transition properties. 2. The increased fuel and oil flows from using higher nitro in four strokes do provide significant cooling. Otherwise, the added heat would, at some point, make running the engine impossible. There are a large number of racers that run 60-70% nitro in their engines and they run no hotter than those using 10%. SignaturePaul McIntosh http://www.rc-bearings.com > Straightly speaking is: higher % nitromethane give more power. More power > is higher rpm and/or higher torque. It depend on the type of model you [quoted text clipped - 25 lines] >> lubricating >> quality?? > Nitromethane do not help ideling. Instead, you need to choose correct > glow plug temperature that really matter the ideling. Because nitro can run very rich, as well as lean, there is a greater tolerance for rich or lean needle settings thus better idling. For the same reason if the mixture varies during transition, then nitro will help with transitition to full power. > Nitromethane also do not help running your engine cooler. Higher power > means more energy is released in the same amount of time. So, your > engine will become hotter. Power is J per second. If you look at some > new model of car engine, will found that the heat sink fin area in > continuing increasing. Some Nove Rossi engine almost use up all area of > the crank case. Nitro does burn hotter than methanol, but only when the engine is at peak or slightly rich of peak. But if you set it richer than that it will run at the same or even cooler temperatures. Power is J per second. But J is not just temperature, if you heat up more mass (kilograms or pounds) per second at the same or slightly cooler temp you will have more heat or power. This is the reason our glow engines develop more power than a gas engine at lower temperatures. Do not confuse heat with temperature. Heat is the flow of energy, temperature is the steady state measurement of potential. You can have a body of hot matter, but there is no heat till that body heats up another body. If you heat up one pound of water one degree and another body two degrees then the first body will have one BTU of heat and the second two BTU's. If you heat one pound of water one degree and another two pounds of water one degree, you will heat up the first one one BTU and the second two BTU's. But the temperature in this latter case the temperature is the same. > Nitromethane do not help ideling. Instead, you need to choose correct > glow plug temperature that really matter the ideling. Because nitro can run very rich, as well as lean, there is a greater tolerance for rich or lean needle settings thus better idling. For the same reason if the mixture varies during transition, then nitro will help with transitition to full power. > Nitromethane also do not help running your engine cooler. Higher power > means more energy is released in the same amount of time. So, your > engine will become hotter. Power is J per second. If you look at some > new model of car engine, will found that the heat sink fin area in > continuing increasing. Some Nove Rossi engine almost use up all area of > the crank case. Nitro does burn hotter than methanol, but only when the engine is at peak or slightly rich of peak. But if you set it richer than that it will run at the same or even cooler temperatures. Power is J per second. But J is not just temperature, if you heat up more mass (kilograms or pounds) per second at the same or slightly cooler temp you will have more heat or power. This is the reason our glow engines develop more power than a gas engine at lower temperatures. Do not confuse heat with temperature. Heat is the flow of energy, temperature is the steady state measurement of potential. You can have a body of hot matter, but there is no heat till that body heats up another body. If you heat up one pound of water one degree and another body two degrees then the first body will have one BTU of heat and the second two BTU's. If you heat one pound of water one degree and another two pounds of water one degree, you will heat up the first one one BTU and the second two BTU's. But the temperature in this latter case the temperature is the same. > degrees then the first body will have one BTU of heat and the second > two BTU's. If you heat one pound of water one degree and another two > pounds of water one degree, you will heat up the first one one BTU and > the second two BTU's. But the temperature in this latter case the > temperature is the same. Really intresting discussion. Give some qualitative analysis here: Nitromethane 4CH3NO2(l) + 3O2(g) → 4CO2(g) + 6H2(g)O + 2N2(g) Methyl Alcohol 2CH3OH(l) + 3O2(g) → 2CO2(g) + 4H2O(g) Both equations use 3O2, 4 molecule of nitromethane were used. But 2 molecule of methyl alcohol were used. Burning of nitromethane produce double volume of gas to burning methyl alcohol. (measured at same temperature and pressure. But before the gas escape the combustion chamber, burning nitromethane likely produce higher temperature and higher pressure. Thas is why higher power.) Pressure * Volume/Temperature is a physical constant. If volume is fixed(limited by the engine displacement), pressure and temperature must increased. Double volume of gas confined in the combustion chamber, exert larger force on the piston. Energy released from burning fuel, partly converted to mechanical energy, partly converted to heat energy. If the fuel input increased, the output energy increase too, both mechanical and heat. > > degrees then the first body will have one BTU of heat and the second > > two BTU's. If you heat one pound of water one degree and another two [quoted text clipped - 12 lines] > Both equations use 3O2, 4 molecule of nitromethane were used. But 2 > molecule of methyl alcohol were used. Burning of nitromethane produce > double volume of gas to burning methyl alcohol. (measured at same > temperature and pressure. But before the gas escape the combustion [quoted text clipped - 9 lines] > energy, partly converted to heat energy. If the fuel input increased, > the output energy increase too, both mechanical and heat. Pressure yes, but only at a slightly higher temperature, and still much less than gas. The real power of nitro is its mass (more mass is more pressure) and its capability of burning without any oxygen added, that is it can be used as a monopropellent. If it becomes contact sensitive, which can happen from corrossion of metal cans, then it will burn with no oxygen. That is why fuel nitro is yellow with a nutty oder instead of clear and little odor as is chemically pure nitro. The yellow color is an indicator that turns purple when it becomes contact sensitive. AA fuel dragsters are taking advantage of its mass and monopropellent capability by injecting as much fuel as possible without hydrolocking. In fact the biggest power boast in the 60's dragsters and the mid to late 70's was the electronic magneto. The stronger spark allowed a richer mixture of nitro which doubled and trippled the power. > Really intresting discussion. Give some qualitative analysis here: > [quoted text clipped - 19 lines] > energy, partly converted to heat energy. If the fuel input increased, > the output energy increase too, both mechanical and heat. What's interesting here is how nitro/methanol fuel does so much of it's work: by producing a larger numbers of combustion product molecules at low heat as opposed to the case with gasoline (octane) based fuels, which produce a smaller number at much greater heat. For gasoline: octane 2 C8H18 + 25 O2 → 16 CO2 + 18 H2O the ratio 'exh. products produced' to 'O2 molecules used' is 1.36 to 1 (34:25). This same ratio for a 50/50 mix of nitro/methanol would be 3 to 1. No wonder racers like using alky/nitro fuel, and like the guy said, it brings its own oxygen, and you get a lot of free cooling too. So, since Press * Vol. = number of molecules * constant * Temperature and Press * Vol. = work, it's clear how nitro/alc. based fuel does most of its work- it increases the pressure in the cyl largely by increasing the number of exhaust molecules. 9% sorry couldnt resist it. > what is the differance between 16% and 25% nitro fuel?? > apart from the 25% being more combustable which has the better lubricating > quality?? > 9% > > sorry couldnt resist it. You'd have been able to if you'd seen all of the thread :-)) SignatureBeav Reply to "beavis dot original at ntlworld dot com" (with the obvious changes) $3.85 |
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