NITRO 4-TEC 3.3
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THE TRX 3.3 RACING ENGINE
High-speed needle (HSN)
- Adjusts the carburetors fuel/air mixture at
high throttle openings.
Idle speed
- The speed (rpm) the engine runs at when the
transmitter’s throttle trigger is at neutral.
Idle speed screw (ISS)
- Located on the carburetor body. This screw
adjusts the idle rpm of the engine.
Lean
- A running condition where the engine is not getting enough
fuel (for the available air). Symptoms include engine overheating,
or the engine runs for a short time and then stalls, particularly at
high speed. This is a dangerous condition that should be corrected
immediately or it can ruin your engine.
Leaning the mixture
- Turning either the high-speed and/or low-
speed needle(s) clockwise to decrease the amount of fuel the
engine receives.
Low-speed needle (LSN)
- Needle valve that controls the fuel mixture
at low throttle openings.
Needle valve
- Valve consisting of a tapered needle that closes
against a corresponding seat to regulate fuel flow.
Nitro
- Abbreviation for nitromethane, a component of model engine
fuel that improves fuel combustion and power output. Nitro also
refers to a class of R/C powered by model engines instead of electric.
Nitro content
- The amount of nitromethane used in the fuel. Usually
measured as a percentage of the total fuel volume. Traxxas engines
are optimized to use 10-20% nitro. 33% nitro may be used for
racing.
Nitromethane
- Nitromethane is a component in the fuel that
increases power from the combustion process up to a point.
Engines are generally optimized to use a range of nitro content for
the best power.
O-ring
- Rubber “O”-shaped ring used as a sealing gasket.
Pipe
- Abbreviation for the tuned exhaust pipe on a nitro engine.
See “Tuned Pipe”.
Piston
- The piston is the internal engine part that is attached to
the upper end of the connecting rod and moves up and down
in the cylinder sleeve. The precise fit between the piston and the
sleeve creates a seal that allows the engine to have the required
compression for combustion.
Port
- Ports are openings in the sleeve that allow atomized fuel to
enter the combustion chamber and burned exhaust gases to exit.
The shape and location of the ports are a large factor in controlling
the engine timing and power output.
Pre-filter
- The outer air filter element in a two-stage air filter. This
provides the first level of air filtration for the engine. The majority
of dirt and debris will be stopped by this filter. Clean, re-oil, and
replace this filter after every hour of run time. Always use both the
pre-filter and primary filter.
Primary filter
- The inner air filter element in a two-stage air filter.
This provides a second level of air filtration after the pre-filter
removes the majority of dirt and debris. Clean, re-oil, and replace
this filter after every 3 - 4 hours of run time. Always use both the
pre-filter and primary filter.
Priming
- Manually causing fuel to move from the fuel tank up to the
carburetor. This is sometimes necessary after the engine has been
sitting for a long period of time and all of the fuel has drained back
to the tank. On a Traxxas model this is done by holding your finger
over the exhaust tip for one or two seconds while the engine is
starting.
Punch
- A term that refers to how quickly the model responds to
throttle input or how quickly it accelerates.
Rich
- A running condition where the engine is getting too much
fuel for the available air. It is better to run an engine slightly rich
to increase engine life. Excessively rich mixtures cause the engine
to have sluggish performance with exaggerated blue smoke and
unburned fuel coming from the exhaust.
rpm
- Abbreviation for Nitro 4-Teclutions per minute (how many
times the engine crankshaft spins in a minute).
Sleeve
- Internal engine part that contains the piston. The precise fit
between the sleeve and the piston creates a seal that allows engine
to have the required compression for combustion. The sleeve in a
TRX engine is made of brass and is then hard-chrome plated.
Slide carburetor
- The throttle on a slide carburetor closes and
opens by sliding a barrel in and out of the carburetor body. This
type of carburetor is preferred for performance use because it
provides a less restrictive “straight-through” air path than the barrel
carburetor design.
Stall
- When the engine stops running, usually due to an incorrect
fuel mixture setting or running out of fuel.
TDC
- Top dead center. The top-most position of the engine
piston stroke.
Tuned pipe
- The tuned exhaust pipe usually consists of a specially-
shaped metal or composite chamber with baffles that is designed to
enhance the power output of the engine.
Wear-in
- Fitment process that occurs during engine break-in where
internal engine parts develop an even more precise matched fit
through actual use under controlled circumstances.
WOT
- Abbreviation for wide-open throttle.
