|Contributed by: Tim Hykaway | Published: January 2004 | Views: 117702 | Email this Article
by: Tim Hykaway
Car Basics Part 1: Fuel Basics
are a lot of mis-conceptions out there about RC
fuels. On the market today there are many brands
of fuel, but most differ with respect to their lubricants
used. The oils used in the RC fuels are essential
to keep all the engine's moving parts working freely
and to remove heat from major moving components.
Lubricants used in nitro RC fuel are either purely
synthetic or castor oil, or a blend of synthetic
oil and castor oil. As everyone knows, a coating
of oil prevents metal parts from rubbing against
one another, and avoids extensive heat build-up
and excessive or premature wear on tightly tolerated
parts(piston and sleeve). The type, quantity and
blend of lubricants in a fuel, are the most closely
guarded secrets in the business and are usually
not disclosed, not even to the distributors. A few
manufacturers are now disclosing lubricant content
(Wildcat, HPI) as in oil % but not in specifics
of how much of each type or even types of oil. Most
manufacturers will just say 12% oil not 6% castor
and 6% synthetic. It seems that more people today
will buy fuels which give oil content so that they
know there engines are getting the required oil
to preserve their investments. Some other major
companies like Traxxas and Blue Thunder still hold
it as their secret. Certain adopted Industry Standards
such as how the fuel is blended by Volume give the
fuel a more exact mixture, where as a few fuel manufactures
still like to blend fuel by weights of ingredients.
oil promotes cooling while Synthetic oil protects
engine components from wear. Some fuels contain
only castor oil and most contain either both types
of oil or only synthetic oils. Big block motors
in my experience have a tendency to favor the castor
oil fuels. This helps them run a little cooler and
crisper, where as smaller engines, which rev a little
higher, like the synthetic blended fuels.
flash point is the temperature at which a lubricant
will burn during combustion in the motor. Lubricants
with a high flash point tend not to burn at all
leaving the engine loaded in oil. As we all know
this will keep the engine well lubed up, but may
affect your performance. Lubes with a lower flash
point tend to burn with the fuel, and this leaves
a cleaner combustion chamber for the next cycle.
You sometimes here people refer to the fact that
your motor seems to have a 4-stroke sound, when
you hear this, this is your motor running slightly
clogged up (this also happens when running fuels
with high oil content, in which the oil isn't burning
PERCENTAGE OF NITRO SHOULD YOU RUN?
you seem to ask has a different opinion of what
type of fuel to use. No fuel is ideal for every
application or is it a fact that a higher percentage
of nitro results in better all round performance.
The correct percentage of nitro in a fuel and its
effects on engine performance are rather complex
issues due to the many variables as in climate,
humidity and glowplugs used. To understand how nitro
content affects engine performance, it helps to
have a little basic understanding of nitro.
is a monopropellant which means it can burn in
the absence of air.
Methane contains nitrogen and oxygen, which provides
more "fuel" for the combustion process
oxygen contained in nitromethane is released during
the combustion process allowing richer needle
settings that pack more fuel in the combustion
fuel plus more air potentially equals more horsepower
when engines are designed to run on fuels containing
nitromethane or the amount of nitromethane that
are a great deal more technical aspects to Nitro
Methane, but this explains why you can produce more
power with it.
Now running more nitro does not always mean more
horsepower, the engine has to be designed to run
the amount of nitromethane you intend to use. Running
30% nitro fuel in an engine designed for low to
no nitromethane content, will not yield anything
but poor, hot running engine characteristics. Using
0% nitro fuel in an engine designed for 20% or higher
nitro will yield equally poor running engine characteristics.
RC cars and trucks with engine sizes .12-->.18
usually use 10%-20% nitro content fuel with 8%-16%
oil content. It is hard for one person to tell you
which fuel to use for your particular vehicle due
the varying conditions of your surrounding area.
If you wish to find out what really works, go down
to your local track to see what everyone uses, that's
the easiest way. RC cars and trucks with engines
from .21-->.27 typically use more nitro content.
The common range is from 20%-40% and around 8%-18%
oil content. Fuels have different oils, and at different
altitudes their flash points are different, so some
people say a particular fuel is good, but for someone
else it is not. It is mostly trial and error for
which fuel will run best for your liking.
RC fuel is a Methanol-based fuel. As people learn
in Chemistry, Alcohol has a very Rapid evaporation
rate. Which given time outside in warm conditions
accelerates that evaporation. If you look at your
fuel bottle on any given day, you will see tons
of tiny droplets on the inside of the bottle. These
tiny droplets are the alcohol (methanol) that is
evaporating out of the fuel. Most people believe
this to be accumulated moisture from the outside
world but its not. If you to some of the serious
racers out there, they say it is a good idea to
keep your fuel in a cooler. This helps keep it cool
on a long day of racing, and also keeps it out of
the sun and humidity.
Since Methanol evaporates so quickly, it is very
important you keep your caps on your fuel bottles,
and also on your quick filler bottles. Even with
the bottle capped, severe changes in climate can
accelerate evaporation inside the bottles. If you
have to store fuel, even for a very short time,
keep it out of the trunk of your car, and off the
basement floor. You want to keep you fuel in an
area where the climate remains relatively constant.
Never store fuel near heat vents or in direct sun
light. Store it in a dark, cool, dry place. When
you store your fuel in the basement, or your garage,
use plywood as an insulator between the bottle and
the floor, because plywood is fairly resistant to
letting moisture through. If you don't have any
plywood, use a thick carpet or even put it up on
Most people believe that keeping fuel in metal containers
is better than plastic ones, but they both have
their flaws. Metal containers are usually roll crimped,
not welded or soldered shut. With these crimps,
they are not 100% sealed, and after time air starts
seeping into the cracks. Plastic seems to seal better
than the metal containers making them the ideal
thing to store fuel in for longer periods of time.
you are careful, and avoid conditions stated above,
you'll be able to safely store fuel and use it up
to two years later.
if you are into RC will never happen!!