If any of these conditions are present, stop immediately and richen the high-
speed mixture 1/4 turn. The engine will probably be slightly rich at that setting
and you can then retune for performance. Always tune for performance by
starting rich and moving toward the ideal setting. Never try to tune from the
lean side. There should always be a light stream of blue smoke coming from
the exhaust.
Before you begin tuning, the engine should be warmed up to its normal
operating temperature and running slightly rich. All final tuning adjustments
must be made to the engine at its normal operating temperature. You can tell
the engine is running rich by noting any of the following:
Sluggish acceleration with blue smoke coming from the exhaust.
There is unburned fuel spraying from the exhaust tip
Leaning the high-speed fuel mixture increases performance
High-Speed Fuel Mixture Adjustment
With the engine warm and running at a rich setting, gradually lean the high-
speed fuel mixture in 1/16 turn increments. Make several high-speed passes
with the Nitro Sport after each adjustment to clear out the engine and note any
change in performance. Continue this procedure until one of the following
conditions exist
:
1.
There is no longer any performance improvement
2.
The engine begins to cut out at high speed
3.
There is a sudden loss of power during acceleration
4.
The engine begins to overheat. Symptoms of
overheating include:
Steam or smoke coming from the engine (not exhaust)
Hesitation or stalling during acceleration
Popping or clattering sound when decelerating
(detonation)
Fluctuating idle speed
Temperature measurement above 300° at the glow plug
If any one of the above conditions occurs, the fuel mixture is already past the
maximum safe lean setting. Richen the fuel mixture to the optimum setting by
richening the high-speed needle at least 1/8 turn counterclockwise and retest.
This setting will extend engine component life.
Low-Speed Fuel Mixture Adjustment
The low-speed mixture is always set after the high-speed needle is correctly
adjusted. The low-speed mixture will be set using the pinch test.
1.
Once the engine is warm, do several high-speed runs to confirm that the
high-speed needle is set correctly.
2.
Bring the vehicle in and pinch closed the fuel line going into the carburetor.
The engine should run for 2-3 seconds, speed up, and then die.
3.
It is very important to make several high-speed runs with the Nitro Sport
between adjustments to clear out any excess fuel. Perform the pinch test
immediately after. If the engine is allowed to idle for a long period of time, it
could “load up” with fuel and give you an inaccurate measurement from
your pinch test.
4.
If the engine runs longer than 3 seconds, then lean the low-speed
needle 1/16 turn, make several more high-speed runs, and retest.
5.
If the engine dies immediately without speeding up, then richen the low-
speed needle 1/8 turn, make several more high-speed runs, and retest.
6.
If the engine dies when you try to accelerate abruptly, then the low-speed
needle is probably set too lean. Richen the low-speed needle 1/8 turn, make
several more high-speed runs, and retest.
7.
When the low-speed needle is set correctly, the engine’s throttle response
should be very quick.
Idle Speed Adjustment
Once the high and low-speed mixtures have been set, reduce the idle speed to
the minimum reliable idle speed. Remember, this adjustment should be made
while the engine is running at normal operating temperature.
1.
Turn the throttle trim on the transmitter so that the brakes are applied. This
ensures that the throttle barrel is resting against the idle adjustment screw.
2.
If necessary, remove the air filter to gain access to the idle adjustment screw.
3.
Turn the screw clockwise to reduce the idle speed, or counterclockwise
to increase it. The idle speed should be set as low as possible while still
maintaining reliable running characteristics.
4.
Reset the throttle trim on the transmitter
Fine-Tuning the Carburetor
After fine-tuning your engine at the end of the break-in procedure, no major
adjustments to the fuel mixture are usually necessary. Make note of the
temperature, humidity, and barometric pressure at the time you finished fine
tuning your carburetor. Current weather conditions can be found online from
national websites, local TV news websites, and Television. This information will
be considered your baseline setting. You may need to adjust your carburetor
needles to compensate for changes in temperature and barometric pressure (air
density) from day to day. Generally, you’ll need to richen the fuel mixture when
the weather is colder than your baseline temperature and the air density is
higher. Lean the fuel mixture when weather is warmer than your baseline
temperature and the air density is lower. The chart below provides general
guidelines on how weather conditions affect air density when they move higher
or lower than your baseline setting.
Tuning The Engine By Temperature
The following procedures require an optional
infrared temperature probe or on-board temperature
gauge (such as the Traxxas on-board digital
temperature gauge (part#4090). Engine 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.
If tuning for maximum performance results in engine temperature exceeding
300°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 in
check, richen the high-speed needle slightly.
Adjusting the Slipper Clutch
The Nitro Sport Special Edition features an adjustable slipper clutch on the spur
gear to protect the drive train from sudden shock loads (such as landing off of
jumps with the engine at full throttle). Under normal conditions the sipper
clutch should not slip. Before adjusting the slipper clutch, turn the model off. Do
not adjust the slipper clutch while the engine is running.
Use the supplied wrench to tighten the slipper nut (clockwise) until it stops and
then back the nut out 1/4 of a turn. If you notice any decrease in performance
after making changes to the slipper clutch adjustment, then it may be too loose.
The slipper must not be allowed to slip during normal acceleration or the
slipper could be damaged.
▼▼
▼▼▼
▼▼▼
EDITION
EDITION
SPECIAL
SPECIAL
Contact Traxxas for assistance: 1-888-TRAXXAS. 972-613-3300 (outside USA). E-Mail us at [email protected]
Page 2
the overall mixture should be...
Slightly richer
Slightly leaner
Leaner
Richer
Richer
Leaner
Richer
Leaner
Richer
Leaner
then the air density is...
Slightly more dense
Slightly less dense
Less dense
More dense
More dense
Less dense
More dense
Less dense
is..
Lower
Higher
Lower
Higher
Lower
Higher
Lower
Higher
Lower
Higher
If the...
Humidity
Pressure (barometer)
Temperature
Altitude
Nitro %