10% to15% Fuel
07-24-2008, 11:06 AM
#26
RE: 10% to15% Fuel
ORIGINAL: JohnW
Nitro is debunked by stating a engine won’t be sluggish for its size burning pure methanol, then one of the two listed solutions is to increase displacement… ummmm ????
Nitro is debunked by stating a engine won’t be sluggish for its size burning pure methanol, then one of the two listed solutions is to increase displacement… ummmm ????
07-24-2008, 12:38 PM
#29
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RE: 10% to15% Fuel
ORIGINAL: wings
You should do more research before posting such nonsense.
Nitro requires LESS oxygen to burn than pure methanol.
This means more fuel and less air (oxygen) is in the cylinder when the engine fires. That means more power.
You should do more research before posting such nonsense.
Nitro requires LESS oxygen to burn than pure methanol.
This means more fuel and less air (oxygen) is in the cylinder when the engine fires. That means more power.
Read a little, it's good for you. You may learn something.
What makes nitro work is that it contains easy to debond oxygen molecules, hence the perceived effects at higher altitudes, since the engine now requires LESS oygen ( which is not so available at the higher elevations. )
Oxygen is used to combust the fuel, so "This means more fuel and less air (oxygen) is in the cylinder when the engine fires..." is pure RUBBISH.
You need an equal amount of fuel to get the same power output, and the oxygen is obtained from the Nitro mix...
Our engines do not "burn" nitro, rather they oxidize the alcohol mix.... that is one reason they WILL run with zero nitro.
This is why the most pronounced effect of Nitro on tuning is at higher elevations, at lower elevations you are merely throwing away money on needless amounts of nitro mix ( unless your engine is problematic for other reasons... ) as the oxygen is already available.
As Downunder posted this has nothing to do with Nitroracers, which is a poor analogy.
And oh, btw, I did not write the material I quoted.
07-24-2008, 02:06 PM
#30
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RE: 10% to15% Fuel
Our engines do not "burn" nitro, rather they oxidize the alcohol mix.... that is one reason they WILL run with zero nitro.
The reason nitro adds power is because you can put a higher mass of heated combustion material though the engine and that is what does the work.
The difference between 15% and 65% nitro fuel was about 1000 rpm, and a full turn on the needle valve. A 40 sized racing engine would burn around 3 oz a minute.
07-24-2008, 02:33 PM
#31
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RE: 10% to15% Fuel
Quoting Downunder:
"There's a generally held belief that if you don't use nitro (or very little) that the engine will be sluggish and underpowered for it's size. This is totally incorrect unless you're into racing where engine size is limited and extreme high performance is necessary. "
"There's a generally held belief that if you don't use nitro (or very little) that the engine will be sluggish and underpowered for it's size. This is totally incorrect unless you're into racing where engine size is limited and extreme high performance is necessary. "
07-24-2008, 02:34 PM
#32
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RE: 10% to15% Fuel
Opjose, No No No. I'm not going to even bother refuting your statements as they are so far off the mark they are obviously incorrect by inspection. Seriously, why do you persist on repeating myths and half -truths backed by pseudo science and misinformed quotes. Nitro is totally misunderstood on how and why it works because people keep repeating incorrect information. Stop it. Someone not qualified to write an article gets nitro all wrong in print then everyone repeats it as truth. I realize you are googleing for any quote that may backup your original incorrect post, but that still doesn’t make you or your quotes correct. It just means you’re good with search engines. For the sake of the forum readers, please stop making up or quoting bogus information until you have verified it from a credible source.
If you honestly want to understand how nitro works, I’d suggest starting with a chemistry class, maybe some research in a credible source like the CRC handbook of Chemistry and Physics, etc. Learn about air/fuel mixtures, energy densities of fuels, etc. Then build the equations and crank the numbers yourself.
If you honestly want to understand how nitro works, I’d suggest starting with a chemistry class, maybe some research in a credible source like the CRC handbook of Chemistry and Physics, etc. Learn about air/fuel mixtures, energy densities of fuels, etc. Then build the equations and crank the numbers yourself.
07-24-2008, 06:19 PM
#33
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RE: 10% to15% Fuel
ORIGINAL: opjose
Oxygen is used to combust the fuel, so "This means more fuel and less air (oxygen) is in the cylinder when the engine fires..." is pure RUBBISH.
Oxygen is used to combust the fuel, so "This means more fuel and less air (oxygen) is in the cylinder when the engine fires..." is pure RUBBISH.
LoL,
If you say so.
ORIGINAL: How Stuff Works
The big advantage of nitromethane is that you can get a lot more power from each explosion inside the engine. Pound for pound, nitromethane is less energetic than gasoline, but you can burn a lot more nitromethane in a cylinder. The net result is more power per stroke. You typically need about 15 pounds of air to burn 1 pound of gasoline, whereas you need only 1.7 pounds of air to burn 1 pound of nitromethane. This means that, compared to gasoline, you can pump about 8 times more nitromethane into a cylinder of a given volume and still get complete combustion.
The big advantage of nitromethane is that you can get a lot more power from each explosion inside the engine. Pound for pound, nitromethane is less energetic than gasoline, but you can burn a lot more nitromethane in a cylinder. The net result is more power per stroke. You typically need about 15 pounds of air to burn 1 pound of gasoline, whereas you need only 1.7 pounds of air to burn 1 pound of nitromethane. This means that, compared to gasoline, you can pump about 8 times more nitromethane into a cylinder of a given volume and still get complete combustion.
http://auto.howstuffworks.com/question642.htm
There is an article by Don Nix, founder of power master fuel that says the same thing.
I am sure there are tons of places that will state the above because it is fact.
I really have no desire to argue with you. I have nothing personal against you.
Its just that facts are facts. I guess we should do the gentlemen's act and agree to disagree. There is nothing more for me to say.
07-24-2008, 09:57 PM
#34
RE: 10% to15% Fuel
My engine runs best on 10% nitro. I get better "miles per gallon" and the engine does not get as hot. I think the extra power from higher nitro content is necessary for people who compete, maybe, but not for sport pilots. I think it's a waste of money to use 15%.
07-24-2008, 10:43 PM
#35
RE: 10% to15% Fuel
It is most certainly is not a waste for sport pilots who typically fly at high density altitudes with low compression engines of which is the most typical of the engines used in the US.
This when it means the differance between getting off the ground or not You will soon understand.
Flagstaffs annual beat the heat flyin occurs this weekend and I checked just this afternoon and temps around 78 degrees renders a density altitude of about 7900 feet. Several of our locals are attending and those in the know are takeing 25% with them and those who don,t have any avaliable are not going to attend with only 10 or 15 avaliable.
John
This when it means the differance between getting off the ground or not You will soon understand.
Flagstaffs annual beat the heat flyin occurs this weekend and I checked just this afternoon and temps around 78 degrees renders a density altitude of about 7900 feet. Several of our locals are attending and those in the know are takeing 25% with them and those who don,t have any avaliable are not going to attend with only 10 or 15 avaliable.
John
07-24-2008, 10:55 PM
#36
RE: 10% to15% Fuel
ORIGINAL: JohnW
Charlie, other way around. Nitro has a higher flame temp than methanol, and by volume it is worse for cooling and power. On the surface, nitro appears to be a terrible fuel. The key to nitro, which many are getting backwards, is that nitro has a very rich optimum air/fuel ratio. Nitromethane has an optimum burn ratio of about 3 parts air to 1 part fuel. Methanol’s optimal burn ratio is about 6 parts air to 1 part fuel. This means pure nitro needs a mixture twice as rich as pure methanol. However, because of nitro’s rich burn ratio, you can cram twice as much fuel into the cylinder per cycle, so that doubles nitro’s cooling and power. This makes up and surpasses the difference between nitro and methanol, hence nitro makes more power. Cooling I’m not too sure on if the benefit is a net gain compared to methanol, but I’ve never really cared. I’m more concerned about power.
A 4% increase in RPM is large. As I touched on and BLE revisited, RPM does not have a linear relationship to RPM. Say you make 10K RPM on 10% and 10.4K RPM on 15%, that is a 4% increase (or 400 RPM) as you indicate. ThrustHP however indicates increasing a prop’s RPM from 10K to 10.4K requires a ~12% increase in power. This means by your own measurements, you gained 12% power by just moving from 10% to 15% nitro.
Nitro increases power.
Charlie, other way around. Nitro has a higher flame temp than methanol, and by volume it is worse for cooling and power. On the surface, nitro appears to be a terrible fuel. The key to nitro, which many are getting backwards, is that nitro has a very rich optimum air/fuel ratio. Nitromethane has an optimum burn ratio of about 3 parts air to 1 part fuel. Methanol’s optimal burn ratio is about 6 parts air to 1 part fuel. This means pure nitro needs a mixture twice as rich as pure methanol. However, because of nitro’s rich burn ratio, you can cram twice as much fuel into the cylinder per cycle, so that doubles nitro’s cooling and power. This makes up and surpasses the difference between nitro and methanol, hence nitro makes more power. Cooling I’m not too sure on if the benefit is a net gain compared to methanol, but I’ve never really cared. I’m more concerned about power.
A 4% increase in RPM is large. As I touched on and BLE revisited, RPM does not have a linear relationship to RPM. Say you make 10K RPM on 10% and 10.4K RPM on 15%, that is a 4% increase (or 400 RPM) as you indicate. ThrustHP however indicates increasing a prop’s RPM from 10K to 10.4K requires a ~12% increase in power. This means by your own measurements, you gained 12% power by just moving from 10% to 15% nitro.
Nitro increases power.
So . . . if I normally fly at 60% throttle when using 15% I can now get away with flying at 72% throttle and save 20% per gallon using 10%. ;-) Still sounds like a deal to me. I only take my Hot Stik above 1/2 throttle in verticals as with 30% of the wing being control surface a full-powered level run causes flutter and a powered dive would eventually rip the control surfaces off.
I solved it a different way by up-engining ( .46 or .51 in a .40 size - same weight or less as they are bored out) and on a couple models swapping out the OEM carb for a Perry. Pays for itself in two seasons at the $5/gallon difference.
To paraphrase our WWII Russian aircraft mfg friends: "Perfection is the enemy of good enough."
