36
Winter Break-in Tips
During the break-in process,the piston and sleeve wear into each
other to form a precise fit.The engine needs to heat up to a
temperature around 200 to 215 degrees to allow the piston and
sleeve to achieve this fit properly.A precise fit between these two
components is critical for proper compression,and optimum
performance.If the engine runs too cold during break-in,the piston
and sleeve will not expand to their appropriate sizes for break-in,
and this can lead to premature wear of these components.This
wear may not become apparent until after winter has past,and the
engine is operated under warmer running conditions.
• Warm the engine to approximately room temperature by
removing all fuel and storing the vehicle inside at room
temperature until just before starting the engine.An extremely
cold engine can become difficult to start.
• After the engine is running, it is important to keep the temperature
of the engine up around 200 to 215 degrees during break-in.
In weather below 45 degrees,the TRX 2.5 engine will tend to run
at lower temperatures between 160 to 180 degrees (when tuned
at proper break-in mixture settings).This is too cool for break-in.
Do not lean the engine to increase engine temperature! This will
also decrease lubrication and cause your piston/sleeve to
wear prematurely.
• Wrap the cooling head with a paper towel,
clean rag or sock to help keep the engine
running around the recommended 200 to
215 break-in temp.If too much heat is
contained,the engine can actually run too
hot.Make sure that you monitor the
engine's temp closely for the first couple
of tanks until you get the right amount of
cover for the cooling head.This will,of course,depend on your
current weather conditions.Adjusting the cover up and down,
exposing more or fewer cooling fins,is a convenient way to
regulate engine temps.
• For owners that do not have access to a temperature probe,a drop
of water on the cooling head (around the glow plug area) should
slowly sizzle for approximately 6 to 8 seconds around 200 to 210
degrees.If the water sizzles for only a few seconds,then it is likely
that it is over 220 degrees,and needs to cool down.If the water
takes a long time or does not evaporate at all,then the engine is
t
o
o c
o
ol.
• We do not recommend that you operate your engine below
35 degrees Fahrenheit.If you insist on running your vehicle
below 35 degrees, just make sure you are aware that nitro engines
may be very difficult to start and tune at those extremely cold
temperatures.Also,at temperatures below freezing,nitro fuel can
actually begin to gel up,and this can be harmful to the engine.
Follow the remaining break-in procedures as outlined in this
manual.This,along with the steps listed above,will ensure a
good break-in for your new nitro engine,and provide many hours
of enjoyment.
Tuning The Engine By Temperature
The following procedures require an
optional infrared temperature probe or
on-board temperature gauge (Traxxas
on-board digital temperature gauge,
part#4091). Engine temperature can be used as an effective tuning
aid when you understand the relationship between engine
temperature and ambient temperature.The engine operating
temperature,when tuned for maximum performance, will vary
according to atmospheric conditions.The atmospheric condition
that has the most influence on engine temperature is air
temperature.Expect the engine temperature to vary almost in
direct proportion to atmospheric temperature.Assuming you tuned
the engine for the same maximum performance each day,the
engine will run about twenty degrees hotter when it’s ninety
degrees outside than it would in seventy-degree weather.For this
reason, we cannot give you a definitive temperature range that
indicates the best possible engine tuning.The temperature gauge
can aid you in tuning by giving you a relative indication of how your
adjustments are affecting the engine and by preventing you from
exceeding maximum engine temperature.For example,as you lean
the fuel mixture,the engine performance will increase along with
the temperature.If you continue to lean the fuel mixture and the
temperature increases but the engine performance does not
change,then you have exceeded the maximum safe lean setting.
Even if it’s 100°F outside,you should be able to tune for maximum
performance.Try to keep your engine from exceeding 270°F when
measured at the glow plug.If tuning for maximum performance
results in engine temperature exceeding 270°F,try to increase
airflow to the engine by cutting out the rear of the body,
windshield,and front valance.If the engine temperature still cannot
be kept below 270°F,richen the high-speed needle slightly.
The TRX 2.5 Racing Engine
