Model Forum / Radio Controlled / Land Models / September 2005

Use Traxxas Top Fuel 20%.  It's designed for the TRX .15 and TRX 2.5 motors
as they have a tendency to run hot.  I run O'Donnels 20% in my trucks.
Trinity also makes a good fuel.  O'Donnels is the most expensive I've seen,
but IMO it's the best.  Runs clean and cool.

The Sig fuel might be a re-badged plane fuel, which has less nitro (usually
10%) and more oil (usually 18%+).  This would run in your Rustler but it
would be a sluggish, smoking pig of a vehicle.  You want at least 20% nitro
and around 12-14% oil.  If you run 25% or the Traxxas 33%, you'll have to
add a head shim to get the compression down or it's snapped rod central!

Doc

Wow, what kind of info are you guys trying to give this guy??? Brands
all have their fans some will swear Traxxas is worthless and to only
use Trinity. Others will tell you exactly the opposite and this goes
for all brands available. BUT the one thing you should NEVER do is
change percentage of nitro from one tank to the next. If the engine is
broken in on 20% stick to 20% for the life of the engine. EVERY
manufacturer of Nitro engines makes this quite clear. Switching will
not blow up your engine or anything that dramatic but it will severly
shorten the life of your engine.

My co-worker said he ran Traxxas 20% in it all its life. Should I stick with
it or run another 20 %  ?
Thanks,
Iowa883

How about this ? Like I said, I wouldn't have any shipping as I work in the
same town and I am there everyday.
check this out :
http://www.sigmfg.com/cgi-bin/dpsmart.exe/MainMenuFV4.html?E+Sig

Thanks,
Iowa883

There is nothing wrong with the Traxxas fuel.  If the truck was used to it,
tuned to it, etc. then run it.  It will make your life much more simple
unless you want to tune things.

My experience (which is not much) - I ran 20% Traxxas in an OS CV-R 12 and a
CV-15 without an issue.  The CV-15 runs 30% now with a colder plug, a little
tuning and kicks a.s.

YMMV

Good luck,

S

Read them at this page too: http://www.btorcboat.com/html/CH3NO2.html

What nitromethane matter:

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, keeping the
maximum power 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. So, higher % nitromethane means less running time.

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 nitromethane matter the engine power:

Nitromethane

4CH3NO2(l) + 3O2(g) → 4CO2(g) + 6H2O(g) + 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. That is why higher power.)

Pressure * Volume/Temperature is a physical constant. If volume is
fixed(that is 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.