Revo • 21
The TRX 2.5R Racing Engine
when voltage is applied. When the engine is being started, the heat from
the glow plug ignites the fuel mixture and starts the combustion process.
Glow plug driver
- This tool clips onto the glow plug and supplies the
required voltage to light the glow plug element. It is also called an igniter.
EZ-Start equipped engines do not require this separate tool.
Header
- The aluminum tube that connects the tuned pipe to the engine
exhaust port. The length and diameter of the header must be carefully
selected to extract the most power from the engine.
High-speed needle
- Adjusts the carburetors fuel/air mixture at high RPM.
Idle speed
- The speed (RPMs) the engine runs at when the transmitter’s
throttle trigger is at neutral.
Idle speed screw
- 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
- Needle valve that controls the low-speed fuel mixture.
Needle valve
- Valve consisting of a tapered needle that closes against a
corresponding seat to regulate fuel flow.
Nitro
- Abbreviation for nitro methane, a component of model engine fuel
that improves fuel combustion and power output. Nitro also refers to a
class of RC powered by model engines instead of electric.
Nitro content
- The amount of nitro methane used in the fuel. Usually
measured as a percentage of the total fuel volume. Traxxas engines are
optimized to use 10-20% nitro. 30% nitro may be used for racing.
Nitromethane
- Nitro methane 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” definition.
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
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 gasses to exit. The shape and
location of the ports are a large factor in controlling the engine timing and
power output.
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 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 revolutions 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.
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.
