R/C Tech Forums - View Single Post - 16% 20% 25% Nitro content???
View Single Post
Old 05-23-2009, 09:38 PM
  #15  
afm
Tech Master
 
afm's Avatar
 
Join Date: Nov 2003
Location: lima-peru
Posts: 1,811
Default

Originally Posted by NitroWD
so...

1. 16% = more compression needed (less shims)
2. 25% = less compression needed (more shims)

which is better? or it's the same?
You are right about compression changes with different nitro contents....which is better depends on what you are looking for

You don’t get fas much RPM’s with 25% nitro as you would with 16%.
With 25% you naturally have to richen the engine, it gives you more low end power due to the 25%...but just not all the power at top speed.
With 16% nitro you can lean it out for more top end power.
Why? because the flame speed of Nitro is much slower than that of Metanol, so by adding Nitro the mixture slows the flame speed. This should not be a problem until you hit very high rpm’s. There's a moment where the engine cannot pickup more rpm’s because it needs to burn the mixture at much higher speed in the combustion chamber. 25% also burns at a lower temp so it will give you advanced timing and therefore more low end power.
With lesser nitro, you may need to lean it a little more and your fuel mileage will be a little better, temps will vary and combustion chamber and carb setup need to be revised, but... more nitro doesn't necessarily mean more power, but yes more fuel consumption and less runtime for the same CC’s.
Higher nitro content does not cool the engine, in fact it creates more heat. Basically, more nitro = more oxidizer to the methanol which in turn creates higher combustion pressures which create more heat.

AFM
afm is offline