Traxxas T-Maxx 4910 Owner's Manual page 34

The TRX 2.5 Racing Engine
Tuning Your TRX 2.5 Engine for Best Performance
When adjusting the
low speed fuel The engine's performance depends on the fuel mixture. Turn the
mixture, it is very
mixture needles clockwise to lean the fuel mixture and
important to make several
counterclockwise to richen it. Leaning the fuel mixture will
high-speed runs with the
increase engine power up to the engine's mechanical limits.
T-Maxx between
Never run the engine too lean (not enough fuel flow). Never
adjustments to clear out any
lean the engine until it begins to cut-out or stall. Leaning the
excess fuel. Perform the
engine beyond the safe allowable limits will result in poor
pinch test immediately after.
performance and almost certain engine damage. Indications
If the engine is allowed to
idle for a long period of time,
of an overly lean mixture include:
it could "load up" with fuel
and give you an inaccurate
measurement from your
pinch test.
If any of these conditions are present, stop immediately and
richen the high speed mixture 1/4 turn. The engine will
For your
probably be slightly rich at that setting and you can then retune
convenience, the
low-speed needle
for performance. Always tune for performance by starting rich
has a positive stop that
and moving leaner toward the ideal setting. Never try to tune
prevents it from being over
from the lean side. There should always be a light stream of blue
tightened and damaging the
smoke coming from the exhaust.
needle and seat. This also
provides an easy way to
Before you begin tuning, the engine should be warmed up to its
gauge how many turns out
normal operating temperature and running slightly rich. All final
from closed the low-speed
tuning adjustments must be made to the engine at its normal
needle adjustment is set to.
operating temperature. You can tell the engine is running rich
by noting any of the following:
When tuning for
performance, watch
closely to notice
when there is no longer any
increase in speed or power
when the high-speed
mixture is lean. If you lean
High-Speed Fuel Mixture Adjustment
the high-speed mixture to
With the engine warm and running at a rich setting, gradually
the point that the engine
lean the high-speed fuel mixture in 1/16 turn increments. Make
cuts-out, hesitates, or stalls,
several high-speed passes with the T-Maxx after each
you are well into the danger
zone and engine damage is
adjustment to clear out the engine and note any change in
likely. Richen the high-speed
performance. The TRX-2.5 is extremely powerful. Remember to
needle 1/4 turn and retune.
apply the throttle gradually to prevent wheelies or loss of
34
Cutting out or sudden loss of power during acceleration.
Overheating (temperature beyond 270° F at the glow plug)
Little or no blue smoke coming from the exhaust.
Sluggish acceleration with blue smoke coming from
the exhaust.
The T-Maxx may not shift into second gear
There is unburned fuel spraying from the exhaust tip
Leaning the high-speed fuel mixture increases performance
control. 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 (Danger!)
3. There is a sudden loss of power during acceleration (Danger!)
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 270° F 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.