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Main Discussion > More Nitro make Engine Hotter or Cooler?
 
 
RCFlyer
Heliman
Location: South Australia

Doe's having more Nitro content in your fuel, make an engine run Hotter or Cooler. I know it will make it run smoother, idle better, and more power, etc. But what happens to the engine temperature?

Thanks, RCFlyer.
02-15-2002 Over year old.
 
 
Doug
Elite Veteran
Location: Naples Florida....

More energy equals more power equals more heat. If run at "best power" in a heli it will incinerate itself. As a result when running on "high" nitro fuel the engine is run quite rich and still makes good power. The extra fuel and oil is a major coolant.
02-15-2002 Over year old.
 
 
maybeim
Senior Heliman
Location: Stockton, California

hotter!
02-15-2002 Over year old.
 
 
Chopper
Key Veteran
Location: Stow,Oh- oops, I mean St Louis, nope Stow again

There were a ton of discussions just like this one on RCO. There were all kinds of people giving all kinds of speculation on this subject. There are a lot of variables: combustion chamber shape, compression ration, and on. I can give you the fuel ratios, and an in depth discertation on the reason why higher nitro runs cooler in our helis, but in very simple terms: it runs cooler. The reason is that you are pushing more fuel through the engine. The fuel air mixture absorbes heat coming in, and it carries more heat away with it. This is not speculation, but fact.

You can skew this conversation and say that a Rossi engine runs hotter with more nitro. Actually it will run terrible with more nitro, but it is not because of the nitro, but because of the engine design. It was designed for low nitro and it runs best on low nitro.

I don't want to get into an egg head debate over this, but if you run an OS, YS or similar Japanese engine, it will run cooler on 30% than on 5%.
02-15-2002 Over year old.
 
 
Alan Szabo Sr
Key Veteran
Location: Las Vegas, Nevada

hotter or colder

I agree with you chopper. From what I can recall Wendell at Powermaster told me the same thing, that nitro is cooling the engine also.
02-15-2002 Over year old.
 
 
Buzzin Brian
Elite Veteran
Location: College Station, Texas

That has been my experience as well. I have ran both 15% and 30 % in the past, and my engines ran cooler on 30% as well as having more power. So needless to say I run 30% religously.

Build it, fly it, crash it. Repeat as often as needed.
02-15-2002 Over year old.
 
 
RappyTappy
Elite Veteran
Location: Las Vegas, NV

More nitro means more power, but also a richer running engine. A richer running engine means better cooling.

Chris
Xero G

Forever Brothers
Mickey Tylo
02-15-2002 Over year old.
HOMEPAGE  
 
 
jbrundt
Veteran
Location: St. Charles, MO

Actually I think it's the fact that nitro has a lower evaporation point than alcohol. Therefore a higher nitro content would offer more cooling since if you remember from your high school chemistry days that evaporation causes cooling.

Higher nitro also means more power being delivered to the moving parts of the engine so the associated stress goes up causing the motor to wear out sooner.

Your engine won't last as long as if you ran it on straight FAI fuel (all things being equal and that you don't run the engine too lean). You have to make some trade offs in this case. Do you want more power or engine longevity?

Jeff
02-15-2002 Over year old.
HOMEPAGE  
 
 
RappyTappy
Elite Veteran
Location: Las Vegas, NV

When you switch from 15% to 30%, you richen up the needles. So, now the engine is flowing more fuel through it, cooling it better, but with the higher nitro it is compensating and still putting out more power than 15%.

Chris
Xero G

Forever Brothers
Mickey Tylo
02-15-2002 Over year old.
HOMEPAGE  
 
 
Doug
Elite Veteran
Location: Naples Florida....

More cooling comes from phase change of a fluid than from conductive cooling. High nitro fuels have more oil per unit volume and use more fuel per second as a result even more oil per second. The oil does not evaporate therefor all cooling by the oil is conductive. The richer mixture insures that the nitro burns first (It caries it's own oxidizer). the alcohol vaporizes and provides phase change cooling. At the end of the day the engine will produce more power over a broader power band with slightly higher piston top and cylinder head temp but lower cylinder wall and crank case temp. but if leaned to best power will rapidly over temp.
02-15-2002 Over year old.
 
 
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Main Discussion > More Nitro make Engine Hotter or Cooler?
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