18 • NITRO RUSTLER
ThE fUEL
Use the Right Fuel
It’s imperative that you use the correct fuel in your
TRX 2.5 Racing Engine for maximum performance
and engine life. Traxxas Top Fuel
®
should be used to
ensure correct engine lubrication, performance, and
ease of tuning. Traxxas Top Fuel has been proven in
thousands of engines, so you can count on it every day
for great performance.
• Top Fuel is the only fuel which is 100% certified for use in
Traxxas engines.
• Traxxas Top Fuel is made with just the right balance of the highest grade
natural and synthetic lubricants to allow excellent throttle response and
the best top-end performance, without sacrificing long-term durability.
• All of the components in the fuel are carefully selected from the
best materials available and then custom blended to match the
metallurgy and temperature characteristics of Traxxas engines.
You may use 10%, 20% or 33% nitro-content fuel. Try to use the same
percentage all the time, avoid switching back and forth between fuels.
We recommend that if you break in your engine on 20% fuel that you stick
with that percentage. If you do move to a higher or lower percentage,
make sure you readjust your fuel mixture to compensate (see below).
Choosing a Nitro Percentage
A commonly asked question is “what is the difference between 10%, 20%,
and 33% fuels?” Increasing the nitro in the fuel is almost like adding extra
oxygen to the combustion process. It burns more efficiently, improves
combustion, and delivers more power. When increased nitro is used, more
of the other fuel components are then required inside the combustion
chamber to maintain the perfect air/fuel ratio. Therefore, overall fuel
mixtures need to be richened slightly (on the high speed needle, about
3/4 of a turn counterclockwise when changing from 20% to 33%, about
1/2 of a turn counterclockwise when changing from 10% to 20%). This
allows greater fuel flow through the engine and promotes cooler running,
even at the maximum lean settings.
If 33% improves power, then it seems that the highest nitro content
available (beyond 33%) should always be used in the engine. In reality,
there are practical limitations. Engines are designed to run best within
a range of nitro percentages. How the engine is ported, the size of the
combustion chamber, and other factors determine how much nitro can
be efficiently used in the engine. The TRX 2.5 Racing Engine responds
well to a maximum of 33% nitro, returning cool temps, more power, and
a smooth throttle response. For those who want to run higher nitro, 33%
Top Fuel is the optimum nitro percentage for the TRX 2.5 Racing Engine.
Increasing the nitro beyond 33% can introduce the need for engine
modifications (ports, head shimming, etc.) to avoid starting and tuning
difficulties. There are limits to how much nitro an engine can effectively
use to make more power. Lower nitro percentages have their own
advantages. Nitro is an expensive component in the fuel, so 10% nitro
blend is more economical for the sport user. 10% also provides greater
latitude with the needle settings for easier tuning.
When using Traxxas Top Fuel, using higher nitro percentages does not
cause the engine to wear out faster. 33% Top Fuel contains the same
quality lubrication package as 10 and 20% Top Fuel. Some non-Traxxas
high-percentage nitro racing fuels do sacrifice some lubrication in
attempts to increase performance. We urge you to not take chances with
your engine investment and use Top Fuel for consistent performance and
long engine life.
What about Other Fuels?
Can other brands of fuel be used besides Top Fuel? There are other fuels
that can provide satisfactory performance; however, there could be long-
term costs in the form of decreased engine performance, loss of tuning
ease, and shorter engine life. Only use fuels that contain both castor and
synthetic oil.
Everyone has an opinion or a claim to make about fuel. The engineering
team at Traxxas has spent years developing TRX Racing Engines. No one
knows more about the specific fuel requirements of Traxxas engines than
Traxxas engineers. We strongly urge you not to take chances with your
engine investment and use the Traxxas fuel made for the TRX 2.5 Racing
Engine.
Handling the Fuel
•
Follow all directions and warnings on the fuel can.
• Keep the fuel tightly capped at all times. Some components in the fuel
can evaporate very quickly and upset the balance of the fuel.
• Do not store unused fuel in the fuel dispenser. Immediately return
fresh unused fuel back into the fuel can.
• Do not mix old and new fuel. Never mix different fuel brands together.
• Store the fuel in a cool dry location, away from any source of heat,
ignition, or combustion.
• Read and follow the safety precautions on page 4 in this manual.
ThE TRx 2.5 RacING ENGINE
DANGER! Model engine fuel
is poisonous to humans and
animals. Drinking the fuel can
cause blindness and death.
Handle with care and respect.
Keep it out of reach of small
children at all times! While
driving, do not leave your
fuel dispensing bottle on the
ground where a child could
have access to it. Follow fuel
label warnings.
