Nitro 4-Tec Owner Manual - Great Hobbies · Thank you for purchasing the Traxxas Nitro 4-Tec.This...

Nitro 4-TecOwner’s Manual

Model4810

Traxxas Corporation, 1100 Klein Road, Plano, Texas 75074, Phone: 972.265.8000, Toll-free 1-888-TRAXXASTraxxas U.K., P.O. Box 1128, Winterbourne, Bristol BS17-2SH, England, Phone: 44.117.956.1002

Internet: www.Traxxas.com, www.ReadyToRun.org

Traxxas CorporationCorporate Headquarters1100 Klein RoadPlano, Texas 75074Phone: 972-265-8000Toll-free 1-888-TRAXXAS

Traxxas U.K.P.O. Box 1128Winterbourne, Bristol BS17-2SHEnglandPhone: 44.117.956.1002

Internetwww.Traxxas.comE-mail: [email protected]

Entire contents ©2003 Traxxas Corporation. Traxxas, Nitro 4-Tec,TRX 2.5, TQ, Top Fuel, EZ-Start, Ready-To-Race, and ProGraphixare trademarks or registered trademarks of Traxxas Corporation.Other brand names and marks are the property of theirrespective holders and are used only for purposes ofidentification. No part of this manual may be reproduced ordistributed in print or electronic media without the expresswritten permission of Traxxas.

020926

2

Thank you for purchasing the Traxxas Nitro 4-Tec. This manualcontains the instructions you will need to operate, and maintainyour Nitro 4-Tec. Look over the manual and examine the Nitro4-Tec carefully before running it. If for some reason you thinkthe Nitro 4-Tec is not what you wanted, then do not continueany further. Your hobby dealer absolutely cannot accept a Nitro4-Tec for return or exchange after it has been run.

The Nitro 4-Tec’s new TRX 2.5 Racing Engine™ is the mostpowerful engine of its size ever available in a Ready-To-Run car.Two years of engineering development, advanced design, andthousands of hours of testing put the TRX 2.5 in a class by itself.Each part of the TRX 2.5 - from the air filter on the slidecarburetor, to the tip on the dyno-tuned exhaust system - hasbeen carefully engineered to provide maximum power over thebroadest RPM range.

Traxxas was the first with standard on-board electric starting.The new second generation EZ-Start has evolved into anincredibly advanced and reliable starting solution, featuringthermal protection for the motor and built-in diagnostics tomonitor the condition of the glow plug.In this manual, we’ll take you step-by-step through all necessaryset-up, break-in, tuning, and operating procedures. Even if youare an experienced R/C enthusiast, it is important for you toread and follow the procedures in this manual. Payparticular attention to the fuel requirements and break-inprocedures. The advanced design of the TRX 2.5 racingengine does not follow traditional old-fashioned thinkingregarding fuel and break-in procedures.

4 Before You Proceed

5 Safety Precautions

6 Tools, Supplies and RequiredEquipment

7 Anatomy of the Nitro 4-Tec

8 Quick Start: GettingUp to Speed

9 Decorating YourNitro 4-Tec Body

10 Installing YourNitro 4-Tec Body

11 The Traxxas TQRadio System

21 The TRX 2.5 racing engine

37 Driving the Nitro4-Tec

38 Adjusting Your Nitro 4-Tec

42 Trouble ShootingYour Nitro 4-Tec

44 Maintainingand Storing Your Nitro 4-Tec

45 Index

3

Introduction

Before You Proceed

Carefully read and follow all instructions in this and anyaccompanying materials to prevent serious damage to yourNitro 4-Tec. Failure to follow these instructions will beconsidered abuse and/or neglect.

Before running your Nitro 4-Tec, look over this entire manual,and examine the car carefully. If for some reason you decide theNitro 4-Tec is not what you wanted, then do not continue anyfurther. Your hobby dealer absolutely cannot accept a Nitro4-Tec for return or exchange after it has been run.

Warnings, helpful hints, and cross-referencesThroughout this manual, you’ll notice warnings and helpfulhints, identified by the icons below. Be sure to read them!

An important warning about personal safety or avoidingdamage to your Nitro 4-Tec and related components.

Special advice from Traxxas to make things easier andmore fun.

Refers you to a page with a related topic.

SupportIf you have any questions about your Nitro 4-Tec or itsoperation, call the Traxxas Technical Support line toll-free at:1-888-TRAXXAS (1-888-872-9927)

Technical support is available Monday through Friday from 8:30am to 9:00pm central time. Technical assistance is also availableat www.Traxxas.com. You may also e-mail customer supportwith your question at [email protected]. Join thousands ofTraxxas R/C enthusiasts in our online community atwww.ReadyToRun.org

Traxxas offers a full-service, on-site repair facility to handle anyof your Traxxas service needs. Maintenance and replacementparts may be purchased directly from Traxxas, or you can saveshipping and handling costs by purchasing them from yourlocal hobby dealer.

4

All of us at Traxxas want you to safely enjoy your new Nitro4-Tec. Operate your Nitro 4-Tec sensibly and with care, and it willbe exciting, safe, and fun for you and those around you. Failureto operate your Nitro 4-Tec in a safe and responsible mannermay result in property damage and serious injury. Theprecautions outlined in this manual should be strictly followedto help ensure safe operation. You alone must see that theinstructions are followed and the precautions are adhered to.

Important Points to Remember R/C fuel is dangerous and highly poisonous. Always follow alldirections and precautions printed on the fuel container.

R/C fuel, especially when in a fuel dispensing bottle, maylook like a cool drink to a child. Keep all fuel out of the reachof children at all times. Do not place fuel containers on theground where children can get to them while you aredriving.

R/C fuel is flammable. Never allow smoking, sparks, heat orflame in the presence of fuel or fuel vapors.

The engine and exhaust system may become extremely hotduring use. Be careful not to touch the parts, especially whenrefueling or stopping the engine.

Prolonged exposure to the engine exhaust can be harmful.Avoid breathing the engine exhaust. Always run your Nitro4-Tec outdoors, in a well-ventilated area. Never run theengine indoors.

Don’t operate your Nitro 4-Tec at night, or anytime your line ofsight to the model may be obstructed or impaired in any way.

Never operate your Nitro 4-Tec in crowds of people or busypedestrian areas. The Nitro 4-Tec is extremely fast, and maycause injury to those unaware of its presence.

Because the Nitro 4-Tec is controlled by radio, it is subject toradio interference from many sources beyond your control.Since radio interference can cause momentary loss ofcontrol, always allow a safety margin in all directions aroundyour model to prevent collisions.

The engine can be loud. If the noise makes youuncomfortable, wear ear protection. Be considerate of yourneighbors by not running your model early in the morningor late in the evening.

Most importantly, use good common sense at all times.▼▼

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All instructionsand precautionsoutlined in this

manual should be strictlyfollowed to ensure safeoperation of your Nitro4-Tec.

The Nitro 4-Tec isnot intended foruse by those under

16 years of age withoutthe supervision of aresponsible andknowledgeable adult.

5

Safety Precautions

Tools, Supplies, and Required Equipment

Your Nitro 4-Tec comes with a set of specialty metric tools. You’llneed to purchase other items, available from your hobby dealer,to operate and maintain your model.

For more info onbatteries, see Usethe Right Batteries

on page 13.

A peak-detectingcharger isrecommended for

best performance andlongest battery life. Formore information, see Use the Right Charger onpage 30.

12 AA alkaline batteries for the radio system

7.2-volt NiCad battery pack for the EZ-Start starting system

NiCad battery charger

Traxxas Top Fuel™10% quart - #5010 • 20% quart - #502010% gallon - #5060 • 20% gallon- #5070

Fuel dispensing bottle (Traxxas part #5001)

TRAXXAS

1.5mm hex wrench

2.0mm hex wrench

Glow plug (universal) wrench

Turnbuckle wrenches

Batteries

Fuel

Supplied ToolsYour Nitro 4-Tec comes with these specialty metric tools:

Other Required Tools and Supplies

Safety glasses

#2 Phillips screwdriver

After-run oil (WD-40™) to protect the engine from corrosion

#1 Phillips screwdriver

Small flat-blade screwdriver (1/8 inch blade)Filter oil (for the foam air filter) see page 27 for details

Hobby knife

6

U-Joint wrench

4-way wrench

Anatomy of the Nitro 4-Tec

Battery Holder

FuelTank

Fuel TankLid

SteeringServo

SuspensionArm

Front BumperPlate

Shock(Oil Damper)

Tie Rod(Turnbuckle)

Throttle/BrakeServo

Receiver

BearingBlock

AirFilter

Pipe

Header

Enginesee pg. 21 for details

PressureLine

FuelLine

EZ-StartMotor

EZ-StartPlug

ShockTower

Body/FoamBumper Mount

Chassis(lower)

7

On/OffSwitch

AntennaMount

PipeHanger

Front Camber Link(Turnbuckle)

RacingTires

Two-SpeedTransmission

BellcrankSteering

FrontDifferential

FrontDrive Belt

Drive BeltPulley

RearDifferential

BodyMount

CenterDrive Belt

The following guide is an overview of theprocedures for getting your Nitro 4-Tec running,

from opening the box to breaking in and tuning your engine.Refer to the pages indicated for details on each step. Look for theQuick Start logo on the bottom corners of Quick Start pages.

1. Charge the battery pack • See sidebar, page 30 The EZ-Start requires a fully charged 7.2-volt battery pack (not included).

2. Get the right fuel • See page 26Use Traxxas Top Fuel™ or consult with Traxxas before using other fuels.

3. Install the antenna • See page 15Install the antenna mast in the Nitro 4-Tec.

4. Decal the body • See page 9You will need to use the body during the break-in process so it’s best to decal it before you use it on the car.

5. Install the body mounts • See page 10Install the body mounts and foam bumper.

6. Install batteries in the transmitter • See page 13The Nitro 4-Tec requires 8 AA alkaline or rechargeable batteries for the transmitter.

7. Install batteries in the model • See page 14The Nitro 4-Tec requires 4 AA alkaline or rechargeable batteries for the receiver.

8. Install the EZ-Start battery • See page 30Install and connect the 7.2-volt battery pack in the EZ-Start controller.

9. Turn on the radio system • See page 18Make a habit of turning the transmitter on first, and off last.

10. Check servo operation • See page 19Make sure the throttle and steering servos are workingcorrectly.

11. Range test the radio system • See page 20Follow this procedure to make sure your radio systemworks properly at a distance and that there is nointerference from outside sources.

12. Fill the fuel tank • See page 26Use your fuel-dispensing bottle to fill the tank.

13. Connect the EZ-Start to the model • See page 31Learn the proper way to use the EZ-Start electric starting system

14. Start the engine • See page 32Learn to use the correct starting procedure for your TRX 2.5.

15. Break-in your engine • See page 32Follow the break-in instructions exactly to ensure the best-performing, longest-lasting engine.

16. Tune your engine • See page 34Learn how to set the fuel mixture needles for optimum engine performance.

17. Drive your Nitro 4-Tec • See page 37Driving tips and adjustments for your Nitro 4-Tec

18. Maintaining your Nitro 4-Tec • See page 44Follow these critical steps to maintain the performanceof your Nitro 4-Tec and keep it in excellent runningcondition.

The Quick StartGuide is notintended to

replace the full operatinginstructions available inthis manual. Please readthis entire manual forcomplete instructions on the proper use andmaintenance of your Nitro 4-Tec.

Quick Start: Getting up to Speed

8

Decorating Your Nitro 4-Tec Body

9

Applying The DecalsThe ProGraphix paintedbody is covered with aprotective film for shipping.You must remove this filmbefore applying any decals.

To remove the film, lift acorner of the film andcarefully pull it off the bodyin one continuous piece.

Your Nitro 4-Tec decals aredie-cut for easy removal. Usea hobby knife to lift thecorner of a decal and lift itfrom the backing.

Carefully position the decalover the desired locationand press one side on thebody. Pull the decal tightand use a finger to graduallysmooth out any air bubblesas you apply the decal.

Look at the photos on the box for typical decal placement.

Installing Body MountsThe body mount parts are located in a separate bag with yourinstructions. The front body mount posts attach to the frontbumper with 3x10mm counter-sunk self-tapping screws. Nowslide the foam bumper over the front mounts, as shown in thedrawing. The excess length of the mounts should be trimmedoff after the body is installed. The rear body mounts attach asshown in the drawing.

10

Installing Nitro 4-Tec Body Mounts

3x10mm CountersunkSelf-tapping screws

FoamBumper

3x14mm WasherheadSelf-tapping screws

Installing RearBody Mounts

Installing FrontBody Mounts

11

The Traxxas TQ Radio System

Your Nitro 4-Tec (model 4810) is equipped with the TQ RadioSystem. The TQ is a 2-channel system that provides high-poweroutput up to a quarter mile and control for two servos. The Nitro4-Tec makes use of two channels for throttle/brake and steering.

Nitro 4-Tec WiringDiagram

AntennaOn/OffSwitch

BlackNegative

RedPositive

Receiver

4-CellBattery Holder

Channel 1Steering Servo

Channel 2Throttle Servo

Channel 2 Channel 1

Battery

CH.2

CH.1

Antenna Throttle Neutral Adjust

Steering Wheel

Throttle Trim

Steering Trim

Power SwitchPower Indicator

Battery Compartment

ServoReversingSwitches

Throttle Trigger

Radio System TerminologyPlease take a moment to familiarize yourself with these radio-system terms. They will be used throughout this manual.

Channel - The 27 MHz frequency band is divided into 6 channelsso that up to six models can be operated simultaneously. Eachchannel is referred to by its flag color and channel number, asshown below.

Clearing your frequency - A routine, verbal check to make surenobody else in your area is operating on the same channel.Always clear your frequency by calling out your channelnumber before operating your model. Wait or move toanother area if your channel is already being used.

Crystal (X-tal) - The plug-in device that determines whichchannel the radio system will operate on. For each channel,there are two crystals, one for the receiver and one for thetransmitter. Of those two crystals, the one marked with thelower number (.455 MHz lower) must be inserted into thereceiver.

Frequency band - The radio frequency used by the transmitterto send signals to your Nitro 4-Tec. All Traxxas RTR modelsoperate on a 27 MHz frequency band.

Neutral position - The standing position that the servos seekwhen the transmitter controls are at the neutral setting.

NiCad - Refers to rechargeable, nickel-cadmium batteries. Themost economical choice, since they may be recharged up to500 times.

Receiver - The radio unit inside your Nitro 4-Tec that receivessignals from the transmitter and relays them to the servos.

Servos - Small motor units in your Nitro 4-Tec that operate thethrottle and steering mechanisms.

Two-channel radio system - The TQ radio system, consisting ofthe receiver, the transmitter, and the servos. The system usestwo channels: one to operate the throttle, one to operate thesteering.

Transmitter - The hand-held radio unit that sends throttle andsteering instructions to your Nitro 4-Tec.

Trim - The fine-tuning adjustment of the neutral position of theservos, made by turning the throttle and steering trim knobson the face of the transmitter.

Channel Frequency Band Flag Color Traxxas Part No.

1 26.995 Brown 2031

2 27.045 Red 2032

3 27.095 Orange 2033

4 27.145 Yellow 2034

5 27.195 Green 2035

6 27.255 Blue 2036

Learn terms relatedto the TRX 2.5racing engine

beginning on page 23.


12

13


Installing Transmitter BatteriesYour TQ transmitter uses 8 AA batteries. The batterycompartment is located at the base of the transmitter.

1. Remove the battery compartment door by pressing thetab and lifting the door up.

2. Install the batteries in the correct orientation as indicatedin the battery compartment.

3. Reinstall the battery door and snap it closed.

4. Turn on the transmitter and check the power indicator fora solid red light.

If the power indicator light flashes, then the transmitterbatteries are weak, discharged or possibly installed incorrectly.Replace with new or freshly charged batteries. The powerindicator light does not indicate the charge level of thereceiver batteries in the model.

Use the Right BatteriesYour transmitter and receiveruse AA batteries. Use newalkaline batteries, orrechargeable batteries such asNiCad or Ni-MH (nickel-metalhydride) batteries in yourtransmitter and receiver. Makesure rechargeable batteries arefully charged according to themanufacturer’s instructions.

If you use rechargeable batteries in your transmitter, beaware that when they begin tolose their charge, they losepower much more quickly thanregular alkaline batteries. Caution: Discontinue runningyour Nitro 4-Tec at the firstsign of weak batteries(flashing red light) to avoidlosing control.

If the power indicatordoesn’t light red, checkthe polarity of the

batteries. Check rechargeablebatteries for a full charge.

CH.2

CH.1

Installing Receiver BatteriesThe radio receiver in your Nitro 4-Tec uses 4 AA batteries. Thereceiver battery holder is located underneath the top plate, justto the right of the fuel tank.

1. Press the tab on the reusable zip tie to release the battery holder.

2. Remove the battery holderand install 4 AA alkalinebatteries. Make careful noteof the battery polarity bycomparing against thediagrams in the batteryholder.

3. Stretch a rubber balloonover the battery holder toprevent fuel contamination.

4. Install the battery holderinto the car and secure it tothe top plate with thereusable zip-tie. Make surethe battery holder is securein the model and will notcome loose. If the tie wrap isloose, it will interfere withthe middle drive belt.

If you userechargeable batteries in your

receiver, be aware thatwhen they begin to losetheir charge, they losepower much more quicklythan regular alkalinebatteries. Signs of weakreceiver batteries includesluggish steering responseand shortened radio range.Caution: Discontinuerunning your Nitro 4-Tec atthe first sign of weakbatteries to avoid losingcontrol.

If the radio systemdoesn’t appear towork when the

transmitter and receiverswitches are turned on,check for correct batteryinstallation.


14

4-cellbatteryholder


15

Spray a little windowcleaner on theantenna wire to

make it easier to pushthrough the antenna tube.

Don’t shorten thelength of theantenna wire. Its

length is tuned to thefrequency band; cutting itcould severely shorten theradio system’s range.

Don’t push thetransmitter antennadown from the top.

Pull it down from thebottom, one segment at atime, to prevent binding andkinking the antenna mast.

Setting Up the AntennaYou must install the antenna mast (tube) before you operateyour Nitro 4-Tec. You’ll find the plastic antenna tube and tip inthe bag with your manuals and documentation.

1. Locate the black antenna wire that exits the receiver. TheNitro 4-Tec receiver is mounted on the side of the upperchassis. The receiver is wrapped in a balloon for protection.The color of the balloon indicates the channel number (seepage 12).

2. Pull the wire straight with your fingers and then insert theend of the wire into one end of the antenna tube. Push thewire all the way through the antenna tube.

3. Pull the remaining wire through the antenna tube, and theninsert the base of the antenna tube into the molded post ontop of the chassis.

4. Fold the remaining antenna wire over the top of the tubeand secure it with the antenna tip.

5. On the transmitter, always fully extend the telescopingantenna when running your Nitro 4-Tec. Make a habit of holding the transmitter so that the antenna points straight up.

Antenna Tip

Antenna Tube


CH.2

CH.1

TQ Radio System Controls

16

Other TQ Radio System AdjustmentsIn addition to the electronic throttle and steering trim controls,your radio system features throttle neutral adjustment andservo reversing switches.

Throttle Neutral AdjustmentThe throttle neutral adjustment is located on the transmitterface and controls the forward/brake travel of the throttletrigger. Change the adjustment by pressing the button andsliding it to the desired position. There are two settingsavailable:

50/50: Allows equal travel for both acceleration and braking.

70/30: Allows more throttle travel (70%) and less

brake travel (30%).

50/50 is the required setting for the Nitro 4-Tec with the TRX 2.5 Racing Engine.

Electronic Throttle TrimThe electronic throttle trim located on the face of thetransmitter adjusts the neutral (center) point of the throttleservo when the servo is at rest. This control has been preset foryou at the factory. If necessary, adjust the control so that thecarburetor is at idle, and the brakes are not applied (the model

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17

will roll freely). Once the engine is running, do not use thethrottle trim to raise or lower the engine idle speed. Make theidle speed adjustment on the carburetor.

Electronic Steering TrimThe electronic steering trim located on the face of thetransmitter adjusts the neutral (center) point of the steeringservo when the servo is at rest. Adjust this control to make themodel drive straight with no steering input at the wheel.

Servo Reversing SwitchesThe servo reversing switches are located on the front of thetransmitter, next to the on/off switch. Moving a switch reversesthe direction of the corresponding servo.

Each switch corresponds to a channel, as shown below. Forexample, if you turn the steering wheel to the right and yourfront wheels turn left, you would move the channel 1 switch tocorrect the servo direction. It may be necessary to adjust thecorresponding trim control after moving a switch.

CH.2

CH.1

Channel Servo1 Steering2 Throttle and braking

TQ Radio System RulesEach time you prepare to run your Nitro4-Tec, you must clear your frequency tobe sure no one else in the area is usingthe same channel as you.

There are six possible channels,numbered 1 through 6. Each isrepresented by a color. Look at thecrystal plugged into the back of yourtransmitter to determine which channelyour car is assigned to.

Always turn your TQ transmitter on first and off last. Thisprocedure will help to prevent your Nitro 4-Tec fromreceiving stray signals from another transmitter, or othersource, and running out of control.

Always have the transmitter and receiver turned on beforeyou start the engine. Never turn the radio system off whilethe engine is running. The on/off switch in the model onlyturns the receiver on and off. It does not turn off the engine.

Always use new or freshly charged batteries for the radiosystem. Weak batteries will limit the range of the radio signalbetween the receiver and the transmitter. Loss of the radiosignal can cause you to lose control of your Nitro 4-Tec.

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▼ Channel 1Brown

Channel 2Red

Channel 3Orange

Channel 4Yellow

Channel 5Green

Channel 6Blue

CH.2

CH.1

1 2 3

Remember, alwaysturn the TQtransmitter on first

and off last to avoid damageto your Nitro 4-Tec.

18



Using the TQ Radio SystemThe TQ Radio System was pre-adjusted at the factory. Theadjustment should be checked, before running the model, incase of movement during shipping. Here’s how:

1. Fully extend the chrome antenna mast on the transmitterand turn the switch on. The red indicator light on thetransmitter should be solid red (not flashing).

2. Turn on the receiver switch in the model. The switch islocated on the rear shock tower.

3. Position the Nitro 4-Tec so that its front wheels are off theground.

4. Turn the steering wheel on the transmitter back and forthand check for rapid operation of the steering servo. Also,check that the steering mechanism is not loose or binding. Ifthe steering operates slowly, check for weak receiverbatteries.

5. When looking down at model, the front wheels should bepointing straight ahead. If the wheels are turned slightly to

the left or right, slowly adjust the steering trim control on thetransmitter until they are pointing straight ahead.

6. Operate the throttle trigger on the transmitter and check forrapid operation of the throttle servo. When the throttletrigger is pulled back, the carburetor should open. When thethrottle trigger is pushed all the way forward, the brakeshould lock.

7. Once adjustments are made, turn off the receiver on yourNitro 4-Tec, followed by the hand-held transmitter.

Brake

Throttle/BrakeServo

Throttle

0°0°

When the engineis running, don’tuse the throttle

trim on the transmitter toadjust the engine idlespeed. Instead, use theidle speed adjustment onthe carburetor.

19

Steering Servo

Nitro 4-Tec ServoOperation


Range-Testing the TQ Radio SystemBefore each running session with your Nitro 4-Tec, you shouldrange-test your radio system to ensure that it operates properly.

1. Turn on the radio system and check its operation as described in the previous section (Using Your Radio System,pages 18- 19).

2. Have friend hold the model with the engine off.

3. Make sure your transmitter antenna is fully extended, andthen walk away from the model with the transmitter until youreach the farthest distance you plan to operate the model.

4. Operate the controls on the transmitter once again to be surethat the model responds correctly.

5. Do not attempt to operate the model if there is any problemwith the radio system or any external interference with yourradio signal at your location.

Don’t attempt tooperate your Nitro4-Tec if there are

any problems with yourradio system or radiointerference at yourlocation.

20

IntroductionThere’s nothing like the TRX 2.5 racing engine in your new Nitro4-Tec. The TRX 2.5 racing engine is vastly superior to typical R/Cengines and belongs in the category of specialty high-performance racing engines. It’s the result of years of focusedengineering development, and thousands of hours of controlled testing and rigorous real-world running. It offersunprecedented power and performance that turns ready-to-runinto Ready-To-Race®.

The TRX 2.5 racing engine takes a total-system approach. Eachpart of the engine, from the air filter to the exhaust tip, iscarefully engineered to work in harmony with other enginecomponents. Each part complements the next, to extractmaximum power. The TRX 2.5 is designed to be tolerant ofvariations in tuning, and to run successfully through a widerange of variable atmospheric conditions, such as changes intemperature, humidity, and altitude.

The TRX 2.5 is manufactured to exacting tolerances and requiresa specially-designed break-in procedure to accomplish the finalprecision fitting of the internal engine components. It is veryimportant that you follow the new break-in procedure as closelyas possible to achieve the best performance and longest lifefrom your TRX 2.5 racing engine. Old style break-in procedures,such as simply running the engine with a very rich fuel mixturefor the first 4 tanks of fuel, will not achieve the best results.Follow the steps in this manual.

A routine maintenance schedule is also required to keep theTRX 2.5 in top running condition. Cleaning the air filter aftereach hour of running is particularly important. Also it isextremely important to perform after-run maintenance on theengine to prevent corrosion of the internal engine components(see page 44).

Traxxas stronglydiscourageschanging or

modifying any part of theTRX 2.5 racing engine. Oldtech tips and tricks thatmay have boosted thepower of other enginescould seriously diminish theperformance of the TRX 2.5.

There’s more advancedthinking, development andtesting in the stock parts ofyour TRX 2.5 than in manyaftermarket manufacturer’sso-called performanceparts. The TRX 2.5 is alreadyone of the most powerfulengines in its class andsimply will not benefit fromaverage, low-tech,aftermarket bolt onperformance items.

The TRX 2.5 Racing Engine

21


TRX 2.5 Illustrated

AirFilter

Head Protector

Head (Cylinder head)

EZ-StartDrive Unit

EZ-StartMotor

Low-SpeedNeedleThrottle

Arm

ClutchBell

Flywheel

Carburetor

Air Intake

Fuel Intake

High-Speed Needle

Idle SpeedScrew

EZ-StartPlug

PositiveWire

NegativeWire

Fuel Line

Fuel TankPipe

ExhaustTip

PressureLine

GroundWire

Glow PlugWire

EZ-StartController

22

Crankshaft

Crankcase

Header

PipeCoupler


Terms to KnowYou’ll find these Nitro R/C engine terms throughout thissection of the manual.

.15 - .15 or “15” refers to the size of the engine. The TRX 2.5 is .15cubic inches or 2.5 cubic centimeters (cc). The name “TRX 2.5”is derived from the cc measurement.

ABC - Abbreviation for aluminum, brass, and chrome. Refers toengine construction that consists of an aluminum piston thatslides in a chrome-plated brass sleeve. The TRX 2.5 uses ABCconstruction.

Air filter - The air filter sits atop the carburetor and preventsharmful dust and dirt from entering the engine. Dirt ingestionis the number one cause of premature engine failure so theengine should never be run without the air filter in place.

Big Block .15 - A .15 (2.5) engine that uses a larger crankcasesize and longer stroke than typical .15 engines. Generally onlyused for specific racing classes.

Break-in - Break-in is the procedure for running a brand newengine according to specific instructions. This correctlyprepares the engine for normal running. The break-inprocedure can be different for different makes of engines.Follow the Traxxas directions for break-in exactly.

Carb - Abbreviation for carburetor.Carburetor - The carburetor atomizes (mixes) the fuel with the

air so that the engine can burn it. There are two types ofcarburetors, slide carbs and barrel carbs. The TRX 2.5 uses thesuperior slide carburetor design.

Clean-out - Cleaning-out is a condition that occurs when theengine is accelerating and the fuel mixture becomessufficiently lean to allow the engine to continue into its upperRPM power band. Usually characterized by a noticeabledecrease in blue exhaust smoke and a dramatic increase inengine speed.

Combustion chamber - The combustion chamber is machinedinto the bottom of the cylinder head. This is where the glow

plug ignites the fuel. The shape of the combustion chamber isdesigned to promote more efficient burning of the fuel.

Connecting rod - The connecting rod transfers the pistonmotion to the crankshaft. The TRX 2.5 racing engine uses a“knife-edged” connecting rod. The aerodynamic, sharpenededges allow it to “slice” through the pressurized air/fuelmixture inside the crankcase.

Cooling fins - The cooling fins are molded into the cylinderhead and crankcase and cause heat to be drawn away fromthe engine. Heat is removed when it dissipates into the airpassing across the cooling fins. It is important to keep the finsclean of dirt and debris for maximum cooling efficiency.

Crankcase - The engine “body” that contains all of the runningmechanical components.

Crankshaft - The main shaft of the engine that contains therotating assembly.

Cylinder head (head) - The finned aluminum part on top of theengine that is responsible for dissipating most of the engine’sheat. The combustion chamber is machined into the bottom ofthe head.

Dyno - Abbreviation for dynamometer. A precise piece oftesting equipment that accurately measures engine powerand torque output over the engine’s entire RPM range.

EZ-Start - Second generation Traxxas on-board electric startingsystem. The system consists of a hand held starter control unitand an on-board gearbox with an electric motor to spin theengine. The new EZ-Start contains many performance andreliability improvements over the first generation EZ-Start.

Filter foam - The oiled foam element inside the air filterhousing. The filter foam in the TRX 2.5 must be thoroughlycleaned and re-oiled after every hour of run time.

Fit - Usually refers to the fit of the piston and sleeve. If the fit istight, then the piston will feel very tight at top of the sleeveand the engine will have good sealing and compression. If thefit is loose, then compression will be low and the piston andsleeve should be replaced.

Learn terms relatedto the TQ RadioSystem on page 12.

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Flame-out - Occurs when the engine stops running at highRPM. Usually the fault of an excessively lean fuel mixture orglow plug failure.

Fuel - (10% 20%) The TRX 2.5 must have model engine fuel torun. Traxxas Top Fuel is recommended. Fuel is sold in quartsand gallons from hobby dealers. The 10 and 20% labelingrefers to the percentage amount of nitromethane contained inthe fuel (see “nitro percentage” definition).

Fuel mixture - The ratio of fuel to air as determined by theneedle settings of the carburetor.

Fuel tubing (fuel line) - The thick silicone tubing that carriesfuel from the fuel tank to the carburetor.

Glow plug - The glow plug is located in the cylinder head at thetop of the combustion chamber. It contains a platinumelement that glows red hot when voltage is applied. When theengine is being started, the heat from the glow plug ignitesthe fuel mixture and starts the combustion process.

Glow plug driver - This tool clips onto the glow plug andsupplies the required voltage to light the glow plug element. Itis also called an igniter. EZ-Start equipped engines do notrequire this separate tool.

Header - The aluminum tube that connects the exhaust systemto the engine exhaust port. The length and diameter of theheader must be carefully selected to extract the most powerfrom the engine.

High-speed needle - Adjusts the carburetors fuel/air mixture athigh RPM.

Idle speed - The speed (RPMs) the engine runs at when thetransmitter’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 gettingenough fuel (for the available air). Symptoms include engineoverheating, 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 canruin your engine.

Leaning the mixture - Turning either the high speed and/orlow-speed needle(s) clockwise to decrease the amount of fuelthe engine receives.

Low-speed needle - Needle valve that controls the low-speedfuel mixture.

Needle valve - Valve consisting of a tapered needle that closesagainst a corresponding seat to regulate fuel flow.

Nitro - Abbreviation for nitro methane, a component of modelengine fuel that improves fuel combustion and power output.Nitro also refers to a class of RC powered by model enginesinstead 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% nitromay be used for racing.

Nitromethane - Nitro methane is a component in the fuel thatincreases power from the combustion process up to a point.Engines are generally optimized to use a range of nitrocontent 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 downin the cylinder sleeve. The precise fit between the piston andthe sleeve creates a seal that allows engine to have therequired compression for combustion.

Port - Ports are openings in the sleeve that allow atomized fuelto enter the combustion chamber and burned exhaust gassesto exit. The shape and location of the ports are a large factor incontrolling the engine timing and power output.

24

Priming - Manually causing fuel to move from the fuel tank upto the carburetor. This is sometimes necessary after the enginehas been sitting for a long period of time and all the fuel hasdrained back to the tank. On a Traxxas model this is done byholding your finger over the exhaust tip for one or twoseconds while the engine is starting.

Punch - A term that refers to how quickly the model respondsto throttle input or how quickly it accelerates.

Rich - A running condition where the engine is getting toomuch fuel for the available air. It is better to run an engineslightly rich to increase engine life. Excessively rich mixturescause the engine to have sluggish performance withexaggerated blue smoke and unburned fuel coming from theexhaust.

RPM - Abbreviation for revolutions per minute (how many timesthe engine crankshaft spins in a minute).

Sleeve - Internal engine part that contains the piston. Theprecise fit between the sleeve and the piston creates a sealthat allows engine to have the required compression forcombustion. The sleeve in a TRX engine is made of brass and isthen hard-chrome plated.

Slide carburetor - The throttle on a slide carburetor closes andopens by sliding a barrel in and out of the carburetor body.This type of carburetor is preferred for performance usebecause it provides a less restrictive “straight-through” air paththan the barrel carburetor design.

Stall - When the engine stops running, usually due to anincorrect fuel mixture setting or running out of fuel.

Tuned pipe - The tuned exhaust pipe usually consists of aspecially-shaped metal or composite chamber with bafflesthat is designed to enhance the power output of the engine.

Wear-in - Fitment process that occurs during engine break-inwhere internal engine parts develop an even more precisematched fit through actual use under controlledcircumstances.

WOT - Abbreviation for wide-open throttle.


25


The FuelUse the Right FuelIt’s imperative that you use the correct fuel inyour TRX 2.5 for maximum performance andengine life. Traxxas Top Fuel should be used to ensure correct engine lubrication,performance, and ease of tuning. Traxxas TopFuel has been proven in thousands of engines,so you can count on it every day for greatperformance.

Top Fuel is the only fuel which is 100% certified for use inTraxxas engines.Traxxas Top Fuel is made with just the right balance of thehighest grade natural and synthetic lubricants to allowexcellent throttle response and the best top-endperformance, without sacrificing long-term durability.All of the components in the fuel are carefully selected fromthe best materials available and then custom blended tomatch the metallurgy and temperature characteristics ofTraxxas engines.

You may use 10% or 20% nitro-content fuel. Use the samepercentage all the time; don’t switch back and forth between10% and 20% fuel. If you break-in your engine on 20% fuel, thenalways use 20% fuel.

What about Other Fuels?Can other brands of fuel be used besides Top Fuel? There areother fuels that can provide satisfactory performance; howeverthere could be long-term costs in the form of decreased engineperformance, loss of tuning ease, and shorter engine life.

Everyone has an opinion or a claim to make about fuel. Theengineering team at Traxxas spent over 2-years developing theTRX 2.5 racing engine. No one knows more about the specificfuel requirements of Traxxas engines than Traxxas engineers. Westrongly urge you not to take chances with your engineinvestment and use the Traxxas fuel made for the TRX 2.5.

Handling the FuelFollow all directions and warnings on the fuel can.Keep the fuel tightly capped at all times. Some componentsin the fuel can evaporate very quickly and upset the balanceof the fuel.Do not store unused fuel in the fuel dispenser. Immediatelyreturn fresh unused fuel back into the fuel can.Do not mix old and new fuel. Never mix different brands offuel together.Store the fuel in a cool dry location, away from any source ofheat, ignition, or combustion.Read and follow the safety precautions on page 5 in this manual.

Filling the Fuel TankUse a fuel dispensing bottle (Traxxas TopFueler, part# 5001) to put fuel into the Nitro4-Tec’s fuel tank. To fill the fuel bottle,squeeze the air out, insert the dispensertip into the fuel can, and release your gripon the bottle. As the bottleexpands, fuel will be drawninto it.

To fill your model flip up thespring-loaded cap on the fueltank, insert the tip of the fuelbottle, and squeeze todispense the fuel. Fill the tankuntil the fuel level reaches the base of the filler neck. Close thefuel tank lid, making sure it closes tightly.

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You may use highernitro percentagesthan 20% in certain

circumstances. Call 1-888-TRAXXAS for moreinformation.

26

The Air FilterThe TRX 2.5 air filter is carefully designed to deliver maximumperformance while protecting your engine from dust and dirt.Use only the supplied filter. You will not improve engineperformance by switching to an aftermarket filter, and youmay risk engine damage due to poor filtration.

The TRX 2.5 air filter assembly consists of 3 pieces:

1. A rubber filter base

2. A plastic housing consisting of a permanently assembledmesh cap and body

3. An oiled foam element

You must clean the filter after every hour of runtime, even if thefilter looks clean. Dust (which is often too fine to see) and dirtconstantly move through the filter anytime the engine isrunning. Even if you can’t see dirt on the filter, it is present insidethe foam after any amount of runtime. If you exceed therecommended cleaning intervals, your engine will be damaged.Engine damage or wear due to dirt ingestion is easy to detect,and one of the top causes of premature engine failure.

Air Filter Cleaning Instructions1. Remove the air filter from the

carburetor bore by pulling the entire filter firmly to theside to release it. Do not pullstraight up.

2. Disassemble the filter. Pull therubber base out of the filterbody.With the base removed, the foam element is visible inthe bottom of the filter body. Pull out the foam element.

3. Clean the filter parts by thoroughly washing all three pieces ofthe filter assembly in hot soapy water (dishwashing detergentworks well). Repeat twice.

4. Thoroughly dry the parts with a clean towel or compressed air.Remember to wear your safety glasses when working withcompressed air.

5. Oil the foam element by saturating it with foam filter oil. Usethe supplied Traxxas filter oil (part# 5263) or a high-quality,special-purpose foam filter oil like what is used for high-performance motorcycle and ATV engines.This type of filter oilis available at motorcycle pro-shops. Never run the enginewithout a properly oiled filter! Apply 30 drops of the Traxxasfilter oil evenly to the top, bottom and sides of the filterelement (30 total drops divided among the 3 surfaces).Squeeze the filter element repeatedly to help spread the oilthroughout. Squeeze the excess oil from the foam.The filterelement should be evenly colored by the oil. Even colorindicates that the oil is evenly distributed. Note: Do not usethe air filter oil for anything other than the air filter. It is notmeant to be a lubricant.

6. Reassemble the filter and install it on the engine, making surethe rubber base fits securely on the carburetor with no gaps orair leaks.


Clean your air filterafter every hour ofruntime to avoid

engine damage, even if thefilter looks clean.

If you usecompressed air todry your air filter

assembly, wear safetyglasses and avoid directingcompressed air towardyour skin.

27


The CarburetorUnderstanding the Carburetor adjustmentsThe carburetor performs several functions. It controls theengine’s speed by restricting the intake of air and fuel into theengine. It atomizes the fuel (suspends the fuel droplets in theair) and also controls the air/fuel ratio of the mixture enteringthe engine (how much air for a given amount of fuel).

To help provide a better understanding of engine tuning andwhy it’s necessary, the following is a brief explanation of theair/fuel combustion process that takes place inside the engine.

In order to create the cylinder pressure that results in power, theengine burns the air/fuel mixture. Both air and fuel, in correctamounts, are needed for proper combustion. It is thecarburetor’s job to mix the air and fuel together (atomize thefuel), in the correct proportion for the best possible combustion.This is the ideal air/fuel ratio. The ideal air/fuel ratio required forthe engine remains roughly constant. Due to variations inatmospheric conditions (temperature, humidity, altitude etc.)fuel flow adjustment valves (called fuel mixture needles) arerequired to meter the fuel and maintain the ideal air/fuel ratio inthese ever-changing conditions. For example, colder air is moredense (more air molecules) for a given volume of air andtherefore requires more fuel (more fuel molecules) to maintain

the correct air/fuel ratio. Warmer air is less dense (fewer airmolecules) and therefore needs less fuel to maintain the correctair/fuel ratio. The tuning needles are there to adjust how muchfuel is made available for the carburetor to mix with theavailable air (atomization).

The Fuel Mixture NeedlesThe amount of fuel metered and atomized by the carburetor iscontrolled by the two mixture needles, the high-speed needleand the low-speed needle. The low-speed needle is used tometer the fuel used by the engine at idle and low RPM (part-throttle) engine speed. The high-speed needle is used to meterthe fuel when the throttle is open from part throttle to wide-open throttle (WOT). Two needles on the TRX 2.5 provide precisecontrol of the air/fuel ratio across the engine’s entire RPM range.

The maximum possible fuel flow is always controlled by thehigh-speed needle. It works like the main water valve on agarden hose. Turn it clockwise to close the valve, counter-clockwise to open it. When the throttle is at idle or partiallyopen, the low-speed needle again meters the fuel flow at theoutlet (needle seat) where the fuel enters the carburetor venturi.This second valve acts like the spray nozzle at the end of thegarden hose in our example. When you accelerate from idle, thethrottle opens and the low-speed needle is pulled away fromthe needle seat. This allows more fuel to flow with the increasedair flow. As the throttle is increased, the low-speed needle is

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See page 35 formore informationon how air density

affects engine tuning.

Air

Fuel

Dense Air Less Dense Air

pulled completely away from the needle seat leaving it fullyopen. At that point, fuel metering is entirely controlled by thehigh-speed needle. Again, using our water hose example, whenthe spray nozzle at the end of our garden hose is fully open,then the main water valve can be used to adjust how fast thewater flows.

The engine’s performance is directly linked to the fuelmixture. Richening the fuel mixture increases the amount offuel in the air/fuel mixture ratio and leaning the fuel mixturedecreases the amount of fuel in the air/fuel mixture ratio.

Slightly lean fuel mixtures deliver stronger, more efficientcombustion and more power, but with less lubrication.

Slightly rich fuel mixtures deliver cooler running and morelubrication but with slightly less power.

Tuning the engine means finding the perfect balance betweenthe two; excellent power to meet your needs while maintaininggood lubrication for long engine life. The optimal fuel mixturesetting is rich to provide a safety margin against having a leancondition if some variable changes (such as the temperaturefrom one day to the next).

General fuel mixture settings are measured by the number ofturns the needles are turned out from fully closed. The fuelmixture settings have been pre-set from the factory to typicalbreak-in settings. Do not readjust your carburetor from thefactory settings until after the engine is started and running,and you have been able to observe the engine running toassess what minor adjustments may be required to compensatefor fuel, temperature, and altitude. Adjustments are usuallymade in 1/8 or 1/16-turn increments.

The Idle Speed AdjustmentThe idle speed screw controls the closed position of the throttleslide. When the throttle servo is in its neutral position, thethrottle slide should be stopped against the idle adjustmentscrew. Always use the idle speed adjusting screw to controlengine idle. Do not use the throttle trim on the transmitter toadjust idle speed. The idle speed should be set as low aspossible and still maintain reliable running.

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Water Valve(Controls Overall Flow)

High Speed Needle

Water Nozzle(Controls Fine Flow)

Low Speed Needle

See Tuning the TRX2.5 for BestPerformance on

page 34 for completeinformation on adjustingthe air/fuel mixture andidle speed.

If your factorypreset carburetoradjustments have

been tampered with, usethe following settings: setthe low-speed needle sothat the screw head is flushwith the end of the slide.Set the high-speed needleto 4 turns out from closed.Always use the factorysettings for initial starting.Only use these settingswhen the factory settingshave been lost.

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Lean Rich


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The Traxxas EZ-Start Electric Starting SystemThe Traxxas EZ-Start brings the convenience of push-buttonelectric engine starting to your Nitro 4-Tec.The EZ-Start consistsof a hand-held control unit and an on-board motorized starter.

Power for the EZ-Start system comes from a 7.2-voltrechargeable NiCad battery pack installed in the hand-heldcontrol unit (battery not included).The engine glow plug is heated automatically by theEZ-Start system, eliminating the need to keep up with aseparate glow plug igniter.The voltage to the glow plug is kept constant, regardless ofthe load placed on the starter by the starter motor.The “Glow Plug” LED (light emitting diode) on the controlunit indicates the condition of the glow plug.The “Motor” LED indicates the status of the EZ-Start electricstarter motor.The cush drive mechanism in the drive unit preventsdamage to the gears caused by engine kickback.Smart Start™ protection circuitry prevents damage to themotor by cutting power if the load on the motor or otherelectronics exceeds safe limits.

Installing the EZ-Start BatteryThe EZ-Start system requires a fully charged 7.2-volt NiCadbattery pack (not included). Use a charger (not included)designed for 7.2-volt battery packs. Charge the batteryaccording to the charger manufacturer’s directions.

1. Press the tab in the end of the battery compartment door to open

2. Plug a fully charged 7.2-volt NiCad battery pack into theconnector inside.

3. Twist the battery 2 or 3 times to twirl the battery plug wires.This helps hold the wire and battery in place when thebattery is installed in the compartment

4. Place the battery into the compartment and press the wiressecurely into place.

5. Slide the battery compartment door back on and lock theend tab.

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Use the Right ChargerThe most convenient

type of charger is an ACpeak-detecting charger thatplugs directly into an ACwall outlet. It containsspecial peak-detectioncircuitry that automaticallyshuts the charger off whenthe battery is fully charged.

If you’re using a 15-minutetimed charger, always fullydischarge the battery packbefore each charge. Somehigh mAh battery packs(1500 mAh or higher)require more than thestandard 15 minutes ofcharge time. If the batterypack is cold after 15 minutesof charging, add another 5minutes of charge time.Closely monitor the batterypack and stop charging itwhen it begins to feel warmto the touch. Never leave abattery chargingunattended. Always followcharger manufacturer’sinstructions.


Using the EZ-StartYour EZ-Start controller plugsinto a 4-prong receptaclemounted on the rear shocktower of your Nitro 4-Tec. Whenthe red button on the controlleris depressed, the EZ-Start motorbegins to spin the engine, andpower from the control unit heats the glow plug. Assuming allsettings and preparations are correct, the engine should startalmost immediately.

Each of the two status indicatorLEDs on the hand-held control unit,the Motor LED and the Glow PlugLED, should light green whilestarting. If either LED fails to lightwhile starting, there is a faultindicated with that function:

If the Glow Plug LED fails tolight, the glow plug may be bad,or the glow plug wire may bedamaged or disconnected.

If the Motor LED fails to lightand the starter fails to operate,then the EZ-Start is inprotection mode.

Protection ModeThe EZ-Start uses Smart Start™ technology to monitor thecondition of the system and detect failures. The controllermonitors the load being placed on the EZ-Start motor. If theload becomes excessive, the system shuts off power to themotor to prevent costly damage to the motor and thecontroller. This may occur, for example, if the engine floods withfuel during starting. The starter spins at first but when excessivefuel in the combustion chamber begins to lock up the engine,the starter motor slows under the heavier load. This causes theprotection circuit to shut off the power to the motor. Allow atleast 3 minutes for the starter motor to cool and the circuit toautomatically reset before continuing. Use the time to find andeliminate the condition that caused the excessive load on thestarter motor.

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When the EZ-Startcontroller is inprotection mode, wait

at least three minutes beforeattempting to start theengine, to give the startermotor time to cool.

It’s normal for yourEZ-Start controller to become warm

after repeated use.

See page 43 for information on clearing a

flooded engine.

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See ImportantPoints to Rememberon page 5 for other

precautions.

Never run yourNitro 4-Tec indoors.Since the TRX 2.5

racing engine exhaustfumes are harmful, alwaysrun your Nitro 4-Tecoutdoors, in a well-ventilated area.

Your TRX 2.5 racingengine doesn’tusually require

priming. If you do need toprime your engine, watchthe fuel line carefully toavoid flooding your engine.See page 43 forinformation on clearing aflooded engine.

Your carburetor ispre-set at thefactory to give the

correct air-to-fuel ratio andidle speed for enginebreak-in. Do not adjust thecarburetor unless youobserve a poor runningcondition that requirescorrection.

Breaking-in Your TRX 2.5 Racing EngineThe TRX 2.5 uses a ringless, aluminum-brass-chrome (ABC)piston/sleeve construction.This type of engine design relies on avery precise running fit between the piston and sleeve for cylindersealing. Engine break-in is necessary to allow the piston andsleeve to develop an extremely precise fit and optimum cylindersealing. Therefore, proper engine break-in is critical to achievingthe fastest, most reliable engine performance.

Allow yourself about 1 to 11/2 hours to complete the break-inprocedure.The engine break-in period will take 5 tanks of fuel in aNitro 4-Tec.The break-in time is not the time to impress yourfriends with your new Nitro 4-Tec. You must wait until the engineis fully broken in before attempting sustained high speedrunning. Patience and careful attention during break-in will rewardyou with the best-performing TRX 2.5 possible.

During break-in, your engine may appear to malfunction withsymptoms like stalling, inconsistent performance, and fouled glowplugs.These are simply the normal “break-in pains” enginessometimes go through.They will disappear once your engine isfully broken in. Many owners report not experiencing any of thesesymptoms with the TRX 2.5. We recommend replacing the glowplug with a new one after the engine break in procedure.

Engine Break-in ProcedureThe focus during break-in is to vary and limit the engine speed.This will be accomplished by accelerating and stopping at differentrates for the first 5 tanks of fuel. As the engine begins to break-in,the duration and intensity of the acceleration will graduallyincrease. Sustained high-speed running is not permitted until the6th tank of fuel. Perform the initial break-in on a large, flat, pavedsurface. Apply all throttle and braking actions gently. Abruptacceleration or braking could cause the engine to stallunnecessarily.

Special break-in fuels are not recommended. Use the same fuelyou plan to use everyday.If possible, avoid breaking-in the engine on extremely hot orcold days.Pay careful attention to the fuel level. Do not allow the fuel tank

to run completely empty. An extremely low fuel level causesthe mixture to run too lean.This could result in a burned glowplug or extremely high engine temperatures.Keep extra glow plugs handy (Traxxas part #3231).The break-inprocess can cause deposits to form on the plug leading to plugfailure.

Follow the instructions exactly for each of the first 6 tanks of fuel.

Starting Your TRX 2.5 Racing Engine for the First TimeBefore you start your TRX 2.5 racing engine for the first time, makesure you have read all instructions and precautions in this manual.Pay close attention to the tank-by-tank break-in instructions inthe next section, and make sure you have read and understoodthem before you run your engine.

Your engine must be at room temperature (70°F or 21° C) orabove the first time you start it. If it’s cooler than roomtemperature outside, keep your Nitro 4-Tec indoors until you’reready to start it, then take it outside.

1. Turn on the radio system according to the instructions on pages 18 and 19.

2. Make sure the throttle is in the idle position.3. Connect the EZ-Start controller according to the instructions on

page 31.4. Press the starter button and watch for fuel moving through the

fuel line up to the carburetor.Watch closely! The fuel moves veryfast. If the fuel doesn’t move through the line within 5 seconds,prime the engine by briefly (one or two seconds) covering theexhaust outlet until the fuel is just visible in the carburetor fuelline. Watch carefully! If the engine is primed too long, it willflood with fuel and stop turning.

5. Once fuel reaches the carburetor, the engine should quickly startand idle.

6. Disconnect the EZ-Start controller from the model.7. Proceed with the engine break-in.

If your engine doesn’t start, see Troubleshooting Your Nitro 4-Tecon page 42.

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33

As you gainexperience in thehobby, you may

discover that many peoplehave differing opinions onwhat is the properprocedure to break-in amodel engine. Only use theTraxxas break-in procedure.Other break-in procedurescould result in a weak,damaged, or otherwise poorperforming engine. Theprocedure outlined herewas extensively tested andproven to yield betterperforming engines thanother “common” break-inmethods. Even if you haveyears of experience usingmodel engines, please donot ignore this caution!

Tank 11. Drive the model with the body off.2. Driving procedure: Gently pull the throttle trigger to 1/4

throttle over a 2-second count. Then gently apply the brake tostop. Count the two seconds out while accelerating: onethousand one, one thousand two, and then stop. Operate thethrottle trigger as smoothly as you can. Repeat this starting andstopping procedure until the first tank of fuel is nearly empty.

3. Look for thick blue smoke exiting the exhaust outlet. If there isno smoke, richen the high-speed needle 1/4 turn, by turning theneedle counterclockwise.

4. When the fuel tank is nearly empty, shut off the engine bypinching the fuel line connected to the carburetor.

5. Let the engine cool for 15 minutes.Note: If at any point the engine cuts out or stalls during gentleacceleration, richen the high-speed needle 1/4 turn by turning theneedle counterclockwise.

Tank 21. From tank 2 forward, the Nitro 4-Tec should be driven with the

body on.2. Driving procedure: Gently pull the throttle trigger to 1/2

throttle over a 2-second count. Then gently apply the brake tostop. Count the two seconds out while accelerating: onethousand one, one thousand two, and then stop. Repeat thisstarting and stopping procedure until the second tank of fuelis nearly empty.

3. When the fuel tank is nearly empty, shut off the engine and let itcool for 15 minutes.

Tank 31. Driving procedure: Gently pull the throttle trigger to 1/2

throttle over a 3-second count. Then gentlyapply the brake to stop. Count the threeseconds out while accelerating: one thousandone, one thousand two, one thousand three,and then stop. Repeat this starting andstopping procedure until the third tank offuel is nearly empty.

2. As the engine loosens, the idle speed may increase and causethe model to try to creep forward when stopped. Reduce theidle speed by turning the idle adjustment (see page 22) on thecarburetor counterclockwise.

3. When the fuel tank is nearly empty, shut off the engine andrefuel. From here on, you do not need to let the engine coolbetween tanks.

Tank 41. Driving procedure: Gently pull the throttle trigger to full

throttle over a 3-second count. Then gently apply the brake tostop. Count the three seconds out while accelerating: onethousand one, one thousand two, one thousand three, and thenstop. Repeat this starting and stopping procedure until thefourth tank of fuel is nearly empty.

2. Apply the throttle gradually! Your finger should not reach fullthrottle until the end of the three-second count.

3. Keep your driving smooth and consistent.4. When the fuel tank is nearly empty, shut off the engine and

refuel.

Tank 51. Driving procedure: Gently pull the throttle trigger to full

throttle over a 3-second count, hold for 2 more seconds, andthen gently apply the brake to stop. Count the five seconds outwhile accelerating. Repeat this starting and stoppingprocedure until the fifth tank of fuel is nearly empty.

2. When the fuel tank is nearly empty, shut off the engine andrefuel.

Tank 6During the sixth tank of fuel, the engine can be tuned for generalperformance use. Proceed to the next section in this manual.

Tank12345

Throttle1/41/21/2FullFull

Time2 Seconds2 Seconds3 Seconds3 Seconds5 Seconds

Cool15 Minutes15 Minutes

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BodyOffOnOnOnOn

NotesApply throttle gradually.Apply throttle gradually.Reduce idle speed if necessary.Keep your driving consistent.Accelerate over 3 second count,hold for 2 seconds.

34


When adjusting thelow-speed fuelmixture, it is very

important to make severalhigh-speed runs with theNitro 4-Tec betweenadjustments to clear out anyexcess fuel. Perform thepinch test immediately after.If the engine is allowed toidle for a long period of time,it could “load up” with fueland give you an inaccuratemeasurement from yourpinch test.

For yourconvenience, thelow-speed needle

has a positive stop thatprevents it from being overtightened and damaging theneedle and seat. This alsoprovides an easy way togauge how many turns outfrom closed the low-speedneedle adjustment is set to.

When tuning forperformance, watchclosely to notice

when there is no longer anyincrease in speed or powerwhen the high-speedmixture is lean. If you leanthe high-speed mixture tothe point that the enginecuts-out, hesitates, or stalls,you are well into the dangerzone and engine damage islikely. Richen the high-speedneedle 1/4 turn and retune.

Tuning the TRX 2.5 for Best PerformanceThe engine’s performance depends on the fuel mixture. Turn themixture needles clockwise to lean the fuel mixture andcounterclockwise to richen it. Leaning the fuel mixture willincrease engine power up to the engine’s mechanical limits.Never run the engine too lean (not enough fuel flow). Neverlean the engine until it begins to cut-out or stall. Leaning theengine beyond the safe allowable limits will result in poorperformance and almost certain engine damage. Indicationsof an overly lean mixture include:

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.

If any of these conditions are present, stop immediately andrichen the high speed mixture 1/4 turn. The engine willprobably be slightly rich at that setting and you can then retunefor performance. Always tune for performance by starting richand moving leaner toward the ideal setting. Never try to tunefrom the lean side. There should always be a light stream of bluesmoke coming from the exhaust.

Before you begin tuning, the engine should be warmed up to itsnormal operating temperature and running slightly rich. All finaltuning adjustments must be made to the engine at its normaloperating temperature. You can tell the engine is running richby noting any of the following:

Sluggish acceleration with blue smoke coming from the exhaust.There is unburned fuel spraying from the exhaust tipLeaning the high-speed fuel mixture increases performance

High-Speed Fuel Mixture AdjustmentWith the engine warm and running at a rich setting, graduallylean the high-speed fuel mixture in 1/16 turn increments. Makeseveral high-speed passes with the Nitro 4-Tec after eachadjustment to clear out the engine and note any change inperformance. The TRX-2.5 is extremely powerful. Remember toapply the throttle gradually to prevent loss of control. Continue

this procedure until there is no longer any performanceimprovement. If any one of the following conditions occurs, thefuel mixture is already past the maximum safe lean setting:

1. The engine begins to cut out at high speed (Danger!)2. There is a sudden loss of power during acceleration (Danger!)3. The engine begins to overheat. Symptoms of

overheating include:

Steam or smoke coming from the engine (not exhaust)Hesitation or stalling during accelerationPopping or clattering sound when decelerating(detonation)Fluctuating idle speedTemperature measurement above 270° F at the glow plug

Richen the high-speed needle at least 1/4 turn counterclockwiseand retune for performance.

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Low-Speed Fuel Mixture AdjustmentThe low-speed mixture is always set after the high-speed needleis correctly adjusted. The low-speed mixture will be set using thepinch test.

1. Once the engine is warm, do several high-speed runs toconfirm that the high-speed needle is set correctly.

2. Bring the vehicle in and pinch closed the fuel line going intothe carburetor. The engine should run for 2-3 seconds, speedup, and then die.

3. If the engine runs longer than 3 seconds, then lean thelow-speed needle 1/16 turn, make several more high-speed runs, and retest.

4. If the engine dies immediately without speeding up, thenrichen the low-speed needle 1/8 turn, make several morehigh-speed runs, and retest.

When the low-speed needle is set correctly, the engine’s throttleresponse should be very quick.

Idle Speed AdjustmentOnce the high and low-speed mixtures have been set, reducethe idle speed to the minimum reliable idle speed. Remember,this adjustment should be made while the engine is running atnormal operating temperature.

1. Turn the throttle trim on the transmitter so that the brakesare applied. This ensures that the throttle slide is restingagainst the idle adjustment screw.

2. If necessary, remove the air filter to gain access to the idleadjustment screw.

3. Turn the screw counterclockwise to reduce the idlespeed, or clockwise to increase it. The idle speed shouldbe set as low as possible while still maintaining reliablerunning characteristics.

4. Reset the throttle trim on the transmitter

Fine-Tuning the CarburetorAfter fine-tuning your TRX 2.5 racing engine at the end of thebreak-in procedure, no major adjustments to the fuel mixtureare usually necessary. Make note of the temperature, humidity,and barometric pressure at the time you finished fine tuningyour carburetor. Current weather conditions can be foundonline from national websites, local TV news websites, andTelevision. This information will be considered your baselinesetting. You may need to adjust your carburetor needles tocompensate for changes in temperature and barometricpressure (air density) from day to day. Generally, you’ll need torichen the fuel mixture when the weather is colder than yourbaseline temperature and the air density is higher. Lean the fuelmixture when weather is warmer than your baselinetemperature and the air density is lower. The chart belowprovides general guidelines on how weather conditions affectair density when they move higher or lower than your baselinesetting (see page 28 for detailed info on how air density affectsmixture settings).

If the...Humidity

Pressure (barometer)

Temperature

Altitude

Nitro %

is..LowerHigherLowerHigherLowerHigherLowerHigherLowerHigher

then the air density is...Slightly more denseSlightly less denseLess denseMore denseMore denseLess denseMore denseLess dense

adjust (correct) the fuel mixture to be...Slightly richerSlightly leanerLeanerRicherRicherLeanerRicherLeanerLeanerRicher

Check the Traxxaswebsite for additionalinformation on base

line settings for your area.

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Tuning the Engine by TemperatureThe following procedures require anoptional infrared temperature probeor on-board temperature gauge(Traxxas on-board digitaltemperature gauge, part#4090).Engine temperature can be used asan effective tuning aid when you understand the relationshipbetween engine temperature and ambient temperature.

The engine operating temperature, when tuned for maximumperformance, will vary according to atmospheric conditions. Theatmospheric condition that has the most influence on enginetemperature is air temperature. Expect the engine temperatureto vary almost in direct proportion to atmospheric temperature.Assuming you tuned the engine for the same maximumperformance each day, the engine will run about twentydegrees hotter when it’s ninety degrees outside than it would inseventy-degree weather. For this reason, we cannot give you adefinitive temperature range that indicates the best possibleengine tuning.

The temperature gauge can aid you in tuning by giving you arelative indication of how your adjustments are affecting theengine and by preventing you from exceeding maximumengine temperature. For example, as you lean the fuel mixture,the engine performance will increase along with thetemperature. If you continue to lean the fuel mixture and thetemperature increases but the engine performance does notchange, then you have exceeded the maximum safe leansetting.

Even if it’s 100°F outside, you should be able to tune formaximum performance. Try to keep your engine from exceeding270°F when measured at the glow plug. If tuning for maximumperformance results inengine temperatureexceeding 270°F, try toincrease airflow to theengine by cutting outthe windshield. If theengine temperature stillcannot be kept below270°F, richen the high-speed needle slightly.


37

Driving the Nitro 4-Tec

IntroductionYour TRX 2.5 racing engine isbroken in, the fuel mixtureis balanced, and the idle isset…now it’s time to havesome fun! This sectioncontains instructions ondriving and makingadjustments to your Nitro4-Tec. Before you go on, hereare some important precautions tokeep in mind.

Don’t run your Nitro 4-Tec through water, mud, snow, orwet grass. Water and mud are easily drawn through the airfilter and will severely damage the engine. Small amounts ofmoisture can cause electronics to fail and loss of control overyour Nitro 4-Tec.

The TRX 2.5 is extremely powerful. Remember to apply thethrottle gradually to prevent wheelies or loss of control.

Don’t hold the Nitro 4-Tec off the ground and rev the engineexcessively with no load on the engine. This practice couldresult in internal engine damage.

Avoid excessive high-speed running for extended periods oftime or over long distances. This could cause the engine tobuild up enough speed to exceed maximum safe RPM limits.

Don’t drive your Nitro 4-Tec with drive train damage of anykind. The engine could be damaged due to overloads on theengine caused by drivetrain friction, or over-revving causedby loose or missing parts.

Don’t tow anything with your Nitro 4-Tec. The engine iscooled by airflow created by speed. Towing creates a highload on the engine, and at the same time limits cooling ofthe engine due to low vehicle speed.

If your Nitro 4-Tec gets stuck, stop driving immediately. Movethe vehicle and then continue driving.

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Once you become familiar with driving your Nitro 4-Tec, you maywish to make adjustments for better driving performance.

Adjusting the Shift PointThe Nitro 4-Tec comes equipped with a two-speed transmission.When the shift point on this transmission is adjusted correctly, itwill maximize acceleration, improve drivability, and minimize laptimes. Use a 2.0mm allen wrench to adjust the shift point.

1. Stop engine.2. Rotate the drum until the access hole is visible from the top.3. Hold the spur gear set, and roll the car forward while looking

through the access hole. Notethat you will see two setscrews through the accesshole as you roll the carforward. The first one holdsthe two-speed mechanism tothe shaft. Do not loosen thisscrew unless you want toremove the two-speedmechanism. The second is theadjustment set screw. Refer to the drawing to identify thescrews.

4. Insert a 2.0 allen wrench through the clutch drum and into the adjustment set screw. (See diagram)

5. Turn the adjustment screw clockwise to raise the shift point(later shifts). Be careful not toovertighten the adjustmentscrew or you may damage thetension spring.

6. Turn the adjustment screwcounter-clockwise to lower shiftpoint (earlier shifts). Be careful notto loosen the adjustment screwtoo much or you may cause thescrew and spring to fall out.

7. Use 1/8 turn increments to find the approximate, desired shiftpoint.

8. Check performance by running a test lap after eachadjustment.

9. Use 1/8-1/16 turn increments to fine tune the shift point.

Alignment SpecsThe Nitro 4-Tec is supplied with soft-compound, race-qualitytires. Due to the high power output of the TRX 2.5 RacingEngine and the high performance nature of the tires, suspensionalignment is critical to achieving maximum tire life. Properalignment promotes even and consistent tire wear as well aspredictable and balanced handling.

CamberThe camber angle of both the front and rear wheels can beadjusted with the camber rods (upper turnbuckles). Use asquare or right-angle triangle to setthe camber accurately. Adjust the frontwheels to 0 degrees of camber (wheelis perpendicular to the ground). In therear, adjust the wheels to 1 to 2degrees of negative camber. Theseadjustments should be set with the carpositioned at its normal ride height.The following information givesrecommended stock alignmentsettings for the Nitro 4-Tec with stocktires and inserts.

• Front Camber Degrees ......-1.0• Rear Camber Degrees ........-1.0• Front Caster Degrees* ........12.0• Front Toe-In Degrees ............0.0

* This setting is achieved by having the 1mmcaster spacer in the front and the 2mm casterspacer in the rear (where the upper suspensionarm attaches to the upper suspension armmount).

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Adjusting Your Nitro 4-Tec

It is important thatyour engine isproperly tuned and

has reached full operatingtemperature before makingshift point adjustments. Stopthe engine before makingadjustments.

The transmissionmay not shift if theadjustment screw is

turned too far in (locked infirst gear), or too far out(locked in second gear). Ifthe car has quickacceleration and does notappear to shift, thetransmission is neverreaching the shift point. Theshift point needs to belowered by turning theadjustment screw counter-clockwise. If the car has pooracceleration but very hightop speed, the transmissionis shifting into second gearalmost instantly. The shiftpoint needs to be raised byturning the adjustmentscrew clockwise.

AccessHole

Drum

-1°-2°

TO

0°FrontCamber

RearCamber

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Toe InSet the steering trim on your transmitter to neutral. Now, adjustyour tie rods so that both wheels are pointing straight aheadand are parallel to each other (0 degrees toe in). This will ensurethe same amount of steering in both directions. If you run out ofadjustment, then the steering servo will have to be re-centered(see centering your servos on page 41).

Fine Tuning the ShocksThe four shocks on your Nitro 4-Tec havethe most influence on its handling.Whenever you rebuild your shocks, ormake any changes to the pistons, springsor oil, always do it carefully and in pairs(front or rear). Piston head selectiondepends on the range of oil viscositiesthat you have available. For example,using a one-hole piston with alightweight oil will give you the samedampening as a two-hole piston withheavier oil. We recommend using theone-hole pistons with a range of oilviscosities from 10W to 50W (availablefrom your hobby shop). The thinnerviscosity oils (30W or less) flow more smoothly and are moreconsistent, while thicker oils provide more dampening. Use only100% pure silicone shock oil to prolong seal life.

The ride height for Nitro 4-Tec can be adjusted by adding orremoving the clip-on spring pre-load spacers. Instead of addingspacers to increase stiffness, use stiffer springs. Adjust the rideheight so that the suspension arms are slightly above beingparallel to the ground. Note that changes in ride height willoccur when the changes in damper angle or spring rates aremade. You can compensate for ride height changes by changingthe pre-load spacers on the dampers. Generally speaking, rideheight should be set as low as possible without causing

significant bottoming of the chassis. Also, in order not to disturbcornering balance, front and rear tire height diameters shouldbe equal. Replace excessively worn tires.

Belt Tension AdjustmentsThe Nitro 4-Tec’s front and middledrive belts are designed to have ahigh initial tension. During the break-in period, the drive belts and pulleyswill “wear in” and the belt tension willgradually decrease. The front andmiddle belt tensions can be tightenedby inserting shims under the frontbearing block. Do not tighten thefront belt tension unless there is morethan 0.25 inch (6mm) deflection at thecenter of the belt (see drawing). Totighten the belt, add the 0.1mm shim first and retest. If the beltis still loose, remove the 0.1mm shim and add the 0.2mm shimand retest. The rear belt tension is adjustable via belt tension

cams in the right andleft rear side plates. Therear belt in the Nitro4-Tec transmits most ofthe engine’s power.Because of the highloading of the rear belt,the tension should bechecked every 3-4hours (20-25 tanks of

fuel) of running. If the rear belt can be deflected more than 0.25¨(6mm) (see illustration), the belt tension cams should be rotatedrearward to the next eccentric slot.

At no time shouldthe body of the carstrike the ground or

interfere with the suspensionor tires. Either situation willcause extremelyunpredictable handling.

Left side plate(Bulkhead)

Right side plate(Bulkhead)

Rear of car Rear of car

.25¨ (6mm)

Using BeltAdjustment Shims


Gear RatiosAnother Nitro 4-Tec feature is the ability to change thegear ratios. Currently, there are three optional gear ratiosfor the Nitro 4-Tec. The stock gear ratio will provide veryhigh (60+ MPH) top speeds. Because of the extreme topspeed, the stock gear ratio is primarily intended for flat-outrunning on large, unobstructed, paved areas. Organized, 1/10scale, nitro touring car racing is typically done on smaller, closedcourses. For this type of racing change to a lower (highernumerical) gear ratio. The following chart gives the four possiblegear ratios sets. The ratios are arranged from highest (lowestnumerical) to lowest (highest numerical). A brief applicationrecommendation follows each gear ratio set.

Nitro 4-Tec gear ratios must be changed as 1st and 2nd gear sets inorder to maintain compatible gear center distances. The gear ratiochart gives the only four compatible ratio choices.

Changing the Clutch Bell Gears1. Remove the right, rear wheel. Remove the E-clip from the

two-speed shaft. Slide the pulley and belt off of the shaft,being careful not to lose the pin that sits under the pulley.Remove the pin. Slide the spur gears off of the shaft (If you

are using optional gears, you may have to loosen the rightchassis stiffener to remove the spur gears).

2. Lock the flywheel with a flatheadscrewdriver to immobilize it. Use a 2.5mmallen wrench to unscrew the caphead

screw that holds the clutch bellto the pilot shaft. Remove theclutch bell.

3. To separate the gears from theclutch bell, gently grip the clutch bell with channel-lock,adjustable pliers. Cover the gears with a cloth to protect theteeth. Using the pliers, unscrew the gears counter-clockwise.

4. New clutch gears simply screw ontothe clutch bell. Reinstall the clutchbell and caphead screw onto thepilot shaft. Reinstall the spur gears,pin, pulley and belt. Secure them onthe two-speed shaft with the E-clip.

5. To adjust the gear mesh, first loosen the four 3x10countersunk hex screws in the slotted holes in the bottom ofthe chassis. Next, remove the two countersunk Phillips headscrews in the bottom of the chassis which hold the slottedengine mount. The engine should now slide back and forth.Slide a strip of thin note paper between the spur gears andthe clutch bell gears. Push the clutch bell gears against thespur gears and tighten the screws on the bottom of thechassis. Remove the paper and the gear mesh is now correctlyadjusted.

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Gear Clutch Spur Primary Overall (MPH) atTeeth Teeth Reduction Reduction 36,000 RPM

Nitro 4-Tec Stock 1st 16 41 2.56 5.81 46.54Equipment 2nd 20 37 1.85 4.19 64.47Ratio Characteristics: Moderate acceleration, highest top speedRecommended Application: Sport/recreational running in very large areas

Optional Clutch Gears 1st 15 41 2.73 6.20 43.6w/Stock Spur Gears 2nd 19 37 1.95 4.41 61.2Ratio Characteristics: Good acceleration, very high top speedRecommended Application: Sport/recreation running in very large areas

Stock Clutch Gears 1st 16 45 2.81 6.38 42.4w/Optional Spur Gears 2nd 20 41 2.05 4.65 58.2Ratio Characteristics: Very good acceleration, high top speedRecommended Application: Sport/recreation, racing on large 1/8 scale size tracks

Optional Clutch Gears 1st 15 45 3.00 6.80 39.8w/Optional Spur Gears 2nd 19 41 2.16 4.89 55.3Ratio Characteristics: Explosive acceleration, moderate top speedRecommended Application: Racing on small tracks. Recreational running in small areas.


Theoretical Speed

Centering the ServosWhenever your radio system has been removed for service or

cleaning, the servos must be re-centered prior to installing theradio system in the model. If the radio system is installed in thecar, disconnect the servo horns from the servos.

Connect the steering servo to channel 1 on your receiver andthe throttle servo to channel 2. The white wire on each servocable is positioned towards the crystal. Connect the red andblack cable from the battery holder to the “batt” terminal on thereceiver. The red wire is positive and the black wire is negative.

Place fresh “AA” batteries in the transmitter and turn thepower switch on. Slide the throttle and steering trimadjustments to to the center position. Now install fresh “AA”batteries into the battery holder and turn the power switch tothe on position. The servos will automatically jump to theircenter positions.

Turn off the battery holder switch followed by the transmitter.The servos are now ready to be installed. Be careful not to movethe servo shaft when reinstalling the servo horns.

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The following section addresses some very basic engine andradio questions you may have about your Nitro 4-Tec. Mostquestions arise from simple user errors or minor adjustments thatare easy to correct. If you can’t find a solution for your Nitro 4-Techere, then visit our Web site at www.Traxxas.com and click on theCustomer Support menu.There you will find a much moreextensive and detailed online troubleshooting area. In addition,you may call Traxxas Customer Service at 1-888-TRAXXAS (outsidethe US call 972-265-8000).

Radio system does not work properly:If the power light on the transmitter does not come on, checkfor proper battery installation and that the batteries are newand/or fully charged. If the power light is blinking, then thetransmitter batteries are weak and should be replaced. Seepage 13 for more details.If the transmitter light is on but the radio is still notresponding, check for proper installation of the receiverbatteries and that the batteries are new and/or fully charged.Check to make sure the on/off switch on the model is in theon position. Finally, if there is still no response check the redand black wires that connect the battery pack to the “batt”terminal on the receiver (you will have to remove the receivercover). Make sure the wires are not pinched or damaged andthat the plug is secure in the receiver. See page 14 for moredetails.

Short radio range:If the radio range appears short, then first check to make surethe transmitter antenna is fully extended and that theantenna in the Nitro 4-Tec is in place and has not been cut ordamaged. Next, make sure the batteries are all fully charged.Finally, if you are still experiencing short range, try a differentlocation. Sometimes there can be interference from varioussources that can cause your radio to malfunction.

Engine will not spin (EZ-Start will not turn the engine):If neither LED on the controller lights, the EZ-Start batterycould be discharged or improperly connected. Inspect andrecharge if necessary.

If the glow plug LED lights and the motor LED does not, thenthe EZ-Start controller is in protection mode. Allow thecontroller to cool for at least three minutes.The circuitryshould automatically reset.Check to make sure the wires are connected to the EZ-Startmotor in the Nitro 4-Tec.The red wire should connect to thepositive motor terminal, indicated by a red dot next to theterminal.The engine could be flooded. If too much fuel accumulates inthe combustion chamber at start up, the engine willhydraulically lock. Follow the procedure on page 40 forclearing a flooded engine.Check for binding at the engine flywheel. If you are not able toturn the engine by hand, the engine could be flooded, therecould be binding in the clutch system, or there could beinternal engine damage. See page 43 for info on clearing aflooded engine and releasing a stuck piston. (Note: It is normalfor the engine to be extremely tight and hard to turn whenthe piston reaches the top of the compression stroke.)

Engine extremely sluggish, hard to start, and will not idleduring tank 1 of the break in:

It is possible that the factory adjusted break-in settings onyour carburetor are too rich for your geographic location,atmospheric conditions, or fuel brand. Extremes intemperature, humidity, barometric pressure, and altitude can’talways be accounted for with a single high-speed needlesetting.The symptoms described above can occur when theair density is very low such as in high mountainous elevations,and extremely cold temperatures. Under these conditions,lean the fuel mixture slightly, 1/8 turn, to see if there is anyimprovement in starting and idling. Only lean the fuel mixturejust until the engine will run and idle reliably and thenproceed with the break in.

The contents of different brands of fuel (other than TraxxasTop Fuel) in combination with extreme atmosphericconditions can also make the factory preset break-in settingstoo rich and cause the symptoms described above. Again, tryleaning the fuel mixture slightly, 1/8 turn, to see if there is anyimprovement in starting and idling.

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Troubleshooting Your Nitro 4-Tec

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Engine spins but will not start:If the engine is spinning but will not start, first check to makesure that both the motor and glow plug LEDs on the EZ-Startcontroller light when the button is depressed. If the glow plugLED does not light, make sure the blue glow plug wire istightly connected and is not damaged in any way. If the wire isgood, then replace the glow plug. It is normal for glow plugs torequire periodic replacement. Only use Traxxas heavy-dutylong glow plugs (part #3231).Check to make sure the fuel is getting to the carburetor.Remove the fuel line where it connects to the carburetor tosee if there is fuel in it. If not, you may need to prime theengine. Reconnect the fuel line and then refer to page 32 forinstructions on priming the engine.Check your fuel mixture settings. It may be necessary to adjustthe fuel mixture if the outside temperature or barometricpressure has changed significantly since the last time the engine was run (see Fine Tuning the Carburetoron page 36).Turn the high-speed needle out(rich/counterclockwise) 1/4 turn, hold the throttle trigger atabout 1/2 throttle and try again to start the engine. Oncestarted, retune the engine for performance (see page 35).The engine could be worn. If the fit between the piston andsleeve is loose, compression is reduced and the engine will bedifficult to start when it is warm, and may tend to stall whenrunning and when the throttle is closed suddenly to idle.Engine life depends on many factors including fuel type, airfilter maintenance, needle settings, and how the engine wasused. For example, if the engine was allowed to ingest dirtfrom lack of air filter maintenance or running through water,then the internal engine components could wear outextremely fast.

Engine performance sluggish:Engine performance depends mostly on the fuel mixturesettings and how they compensate for the currentatmospheric conditions. Before you suspect other failures withthe engine, richen the high-speed needle at least 1/4 turn andthen retune the engine for performance (see page 35).Try a new Traxxas 3231 glow plug. Sometimes a glow plug willwork well enough to start the engine but not be able todeliver the engine’s full performance potential.

If the fuel mixture seems to be set correctly, make sure the fuelis fresh. If the fuel is old, or was left uncapped for a long period,then some of the important fuel components could haveevaporated.Try new, fresh, Traxxas Top FuelCheck to make sure there is no binding in the driveline thatwould cause excessive loads on the engine.

Clearing a Flooded Engine:If the engine is primed for too long during startup, then it canbecome flooded with fuel.When the engine is flooded it will nolonger turn due to excess fuel in the combustion chamberpreventing upward movement of the piston. Use the followingprocedure to clear a flooded engine.

1. Remove the blue glow plug wire.2. Remove the glow plug and gasket with the glow plug wrench

supplied with your model. A 5/16 nut driver will also work.3. Turn the model upside down and plug in the EZ-Start controller.4. Push the EZ-Start button for several seconds to clear the engine

of excess fuel5. Turn the model over and reinstall the glow plug and gasket.6. Reconnect the blue glow plug wire to the glow plug.7. Reconnect the EZ-Start controller8. Do not prime the engine. Pull the throttle to 1/2 throttle and

push the EZ-Start button.The engine should start immediately.

Piston Stuck at Top Dead Center (TDC):A new engine will typically have a tight fit between the piston andthe top of the sleeve.This is a tapered fit.The fit should not be tootight to start the engine, however a weak starter battery or onethat has not been charged fully may not deliver enough power tocrank the engine over at the appropriate RPM to keep the pistonfrom sticking. Make sure that you are using a good quality batterypack that is fully charged.This is especially important with a newengine that needs to be broken-in. If the engine is stuck at TDC,then use a pair of needle nose pliers to grasp the flywheel fromthe bottom of the engine. Rotate the flywheel counter-clockwisewhen viewed from the front of the engine.You should see theflywheel turn and you should feel the piston become unstuckfrom the sleeve. Before trying to restart the engine replace thestarter battery with a freshly charged pack or a freshly chargedbattery pack of better quality.

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Troubleshooting Your Nitro 4-Tec

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Your Nitro 4-Tec requires timely maintenance in order to stay intop running condition. Neglecting the maintenance could allowdirt, deposits, and moisture to build up inside the engineleading to internal engine failure. The following proceduresshould be taken very seriously.

After each hour of running:Clean and re-oil the air filter.The instructions for thisprocedure are on page 27. We cannot stress enough thevalue of cleaning your air filter at the scheduled intervals.Do not neglect your air filter maintenance!

Clean the outside of the engine of accumulated dirt, oil, andgrime. Accumulated grime will decrease the engine’s ability tocool itself.

After each running session:Perform after-run maintenance on the engine.This clears theengine of destructive moisture and other corrosive deposits.This is extremely important for the life of the engine. Seepage 42 for after-run maintenance procedures.

Inspect the vehicle for obvious damage or wear. Look for:1. Loose or missing screws2. Cracked, bent, or damaged parts 3. Cut or loose wiring 4. Cut or kinked fuel lines5. Signs of fuel leakage

Inspect the gears for wear, broken teeth, or debris lodgedbetween the teeth.

Other periodic maintenance:Piston/sleeve: The life of the piston andsleeve will vary greatly with how theengine was used and maintained.Thepiston and sleeve should be replacedwhen they no longer seal effectively(loss of compression). Symptoms includethe engine being difficult to start whenwarm, stalling when warm, and stallingwhen throttle is suddenly closed to idle.Replace the wrist pin and G-clipwhenever the piston and sleeve arereplaced.

Connecting rod: The connecting rodshould be replaced when the piston andsleeve are replaced or after three gallonsof fuel, whichever comes first. Alsoreplace the piston wrist pin and G-clip whenever theconnecting rod is replaced. As with other internal enginecomponents, connecting rod life depends engine’s usageand the quality and frequency of the engine maintenance.

EZ-Start: The cush drive elements in the EZ-Start driveunit should be inspected after 3-gallons of fuel. If the cushdrive elements appear deformed or hardened they shouldbe replaced. Inspect the EZ-Start gears for any signs ofwear. Damaged gears should be replaced. Coat the gearswith a thin layer of white lithium grease.

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Maintaining and Storing Your Nitro 4-Tec

If the engine isworn or damagedenough to require

replacing the piston,sleeve, or connecting rod,consider exchanging yourold engine for a brand newengine under the terms ofthe Traxxas Lifetime EngineReplacement Plan (ERP). Itcould save you time andeffort. Details are in yourmodel’s documentationpackage or on our website.

The TRX 2.5 isdesigned to be easyto rebuild. Critical

engine components suchas the crankcase,crankshaft, and enginebearings are made toextremely high qualitystandards and shouldunder normalcircumstances outlastmultiple sets of pistons,sleeves, connecting rods,and wrist pins(reciprocating assemblies).It could be moreeconomical for you tocontinue to use your goodbearings and crankshafts,and simply replace thereciprocating assembly asneeded. Engine assembly isnot difficult and replacingthe reciprocating assemblydoes not require anyspecial tools or skills.

45

Maintaining and Storing Your Nitro 4-Tec

After-run ProcedureYou must perform after-run maintenance on your Traxxasengine whenever the model will be stored for longer than a fewhours. Taking the time to prepare your engine for storage willreward you with longer engine life, easier starting, and betterperformance.

When a nitro engine is shut off, some excess unburned fuelremains in the engine. The methanol in model engine fuel ishygroscopic, which means it easily attracts and absorbsmoisture. This moisture can cause rust and corrosion on thesteel engine parts (crankshaft, bearings, wrist pin and startershaft) if the fuel is not removed from the engine. There are afterrun oil products available from your hobby dealer or you canuse WD-40™, a common household lubricant. To ensure your TRX2.5 racing engine is protected from internal corrosion, use thefollowing procedure:

1. Whenever possible, shut off the engine by pinching the fuelline closed. This allows most of the excess fuel to beconsumed by the engine. Be sure the throttle is in the idleposition. You may have to pinch the fuel line closed forseveral seconds before the engine stops.

2. Completely empty the fuel tank. Use your fuel-dispensingbottle to suck out the old fuel. Do not mix the old fuel withyour fresh fuel supply. If you leave fuel in the tank,transporting or handling your Nitro 4-Tec may cause fuel torun into the engine.

3. With the fuel tank empty and the throttle at the idleposition, try to start the engine. The engine will most likelystart and run for a few seconds as it uses up any fuelremaining in the engine and fuel lines.

4. Once the engine stops, clean the outside of the engine withcompressed air or spray motor cleaner. Once the engine isclean and dry, remove the glow plug power wire, glow plug,and air filter.

5. Open the throttle fully and spray a one-second burst ofWD-40 into the carburetor and into the glow plug hole(Caution! Wear safety glasses to prevent spray from gettinginto your eyes).

6. Place a rag or paper towel over the engine to catch anyWD-40 that may come out the carburetor or glow plug hole.

7. Connect the EZ-Start controller to the model and spin theengine for 10 seconds.

8. Remove the rag or paper towel and repeat steps 5–7 twomore times.

9. Clean and re-oil the air filter so it will be ready for use nexttime. See page 27 for air filter maintenance instructions.

10. Replace the glow plug, reconnect the glow plug power wire,and reinstall the air filter.

Denatured alcohol(available fromhome centers and

paint supply stores) in aspray bottle is an extremelyeffective cleaner. Be sure towear safety glasses andgloves when working withdenatured alcohol.

Fun fact: WD-40™

stands for “waterdisplacement

attempt #40.” The WD-40™

product used today was thesuccessful 40th attempt atcreating a water-displacinglubricant. WD-40™ was thelab test label.

Be sure to followproper maintenanceand storage

procedures to avoiddamage to your engine andother components of yourNitro 4-Tec.

Don’t put the fuelfrom your tank backinto your fuel jug.

Dispose of it properly,following city or countyregulations.

Always wear eyeprotection whenusing compressed

air or spray cleaners andlubricants.

46

Index

ABC 23After-run maintenance 21, 44, 45After-run procedure 45Air density 28, 35Air Filter 7, 22, 23, 27, 35, 44, 45

Cleaning 21, 27foam 23maintenance 43oil 6

Air Intake 22Air temperature 36, 43Air/fuel mixture 28Air/fuel ratio 28, 29, 32Airflow 36Alignment 38Ambient temperature 36Antenna (receiver) 11, 15, 42

tip 15tube 15wire 15

Antenna (transmitter) 11, 15, 42Antenna Mount 7Atmospheric conditions 28, 36, 43Axle pins 9Barometric pressure 35, 43Baseline setting 35Batteries 6, 12, 13, 14, 42-43

charging 30installing 14receiver 13, 14rechargeable 13, 14transmitter 13

Batteries, Ni-MH (nickel-metal hydride) 13Batteries, NiCad (nickel-cadmium) 6, 12, 13, 30Battery box 7Battery compartment (Transmitter) 11, 13Battery holder 11Bearing Block 7Bearings 45Big Block .15 23Binding 43Body mount 7, 10Brake 19Bumper (Foam) 10Camber 38Carb, see also Carburetor 23Carburetor 22, 23, 28, 43

adjustments 28barrel 23fine-tuning 35slide 25venturi 28

Channel 11, 12, 17, 18Channel number 12Charger 6, 30

peak-detecting 30timed 30

Chassis 7Clean-out 23Cleaning 44Clearing your frequency 12Clutch bell 22, 40

gears 40Combustion 28Combustion chamber 23Compression 24, 43, 44Connecting rod 23, 44Cooling fins 23Crankcase 22, 23Crankshaft 22, 23, 45Crystal 12, 18Customer service 4, 42-43Cylinder sealing 32Decals 9Drive Belt 7, 39

tension 39Drivetrain friction 37Dyno 23E-mail 4Engine, TRX 2.5 7, 22, 26

"cutting out" 34break-in 21, 23, 32

driving procedure 33cooling 36, 44damage 27detonation 34failure 27, 44flooding 31, 42-43hesitation 34life 43, 44maintenance 44overheating 34performance 29priming 25, 32, 43

revving 37shut off 45sluggish acceleration 34stalling 25, 32, 34, 43, 44temperature 34, 36terms 23tuning 28, 34

by temperature 36Exhaust 5, 22Exhaust fumes 32EZ-Start 6, 23, 24, 30, 42

“glow plug” LED 30, 31, 42, 43“motor” LED 30, 31, 42, 43battery 30, 42controller 22, 31, 42, 43, 45cush drive 30drive unit 22motor 7, 22, 31, 42plug 7, 22Protection Mode 31, 42-43Smart Start™ 30, 31

Fit 23Flag color 12Flame-out 24Flooding, see Engine; floodingFlywheel 22, 42-43Frequency band 12, 15Fuel 5, 6, 24, 26, 43, 45

break-in fuel 32fuel dispensing bottle 6, 26

Traxxas Top Fueler 26Traxxas Top Fuel 24, 26, 43unburned 45

Fuel flow 28Fuel intake 22Fuel line (fuel tubing) 7, 22, 24, 43Fuel mixture adjustment 35

high-speed fuel mixture 34low-speed mixture 35

Fuel mixture, see also air/fuel mixture 24, 34,35, 43Fuel tank 7, 22, 26, 45

emptying 45filling 26fuel level 32tank lid 7

Gear Ratios 40

47

Glow plug 24, 30, 31, 32, 34, 43driver 24fouled 32igniter 30power wire 22, 43, 45

Ground wire 22Head (cylinder head) 22, 23Head Protector 22Header 7, 24Hex hubs 9Humidity 35Idle adjustment screw 35Idle speed 17, 24, 29, 32, 33, 34, 35Idle Speed Adjustment 29, 33, 35Idle Speed Screw 22, 24, 29Jumping 37Lean 24, 29

leaning the mixture 24maximum safe lean setting 34-35, 36

Lubrication 29Maintenance 44Maintenance schedule 21Methanol 45Mixture needles 34

high-speed needle 22, 24, 28, 35, 43low-speed needle 22, 24, 28, 35

Moisture 44, 45Needle seat 28Needle settings 43Needle valve 24Negative wire 22Neutral (center) point 16-17Neutral position 12Nitro 24

content 24, 26percentage 26

compensating for 35Nitromethane, see also Nitro 24O-ring 24Oil 6

after-run 6, 45filter 6WD-40™ 6, 45

On/Off switch 7, 11, 18, 42-43Over revving 37Peak detection, see ChargerPinch test 35

Pipe (tuned) 7, 22, 24, 25Pipe hanger 7Piston 24, 32

wrist pin 44, 45stuck 43

Piston and Sleeve 43, 44Port 24Positive Wire 22Power Switch 11Pressure Line 7, 22Priming, see Engine; primingProGraphix 9Pulley 7Punch 25Quick Start 8, 9, 10, 13, 14, 15, 18, 19, 20, 26, 30, 31, 32, 34, 37Radio interference 5, 20Radio System 11, 12, 19, 42-43

adjustments 16controls 16range-testing 20rules 18terminology 12terms 12

Range 14, 15, 18, 20, 42-43short 42-43

Receiver 11, 12, 42cover (box) 7, 42-43

Required equipment 6Rich 25, 29RPM 25

limits 37Safety 5Servo reversing switches 11, 16Servos 7, 11, 12, 41

centering 41reversing 11, 17steering 7, 11, 17, 19throttle/brake 7, 11, 16-17, 19

Shift point 38Shipping 4Shock Tower 7Shocks 7, 39

fine tuning 39Sleeve 25, 32Smoke 34Stalling, see Engine; stalling

Starter shaft 45Starting, see Engine; startingSteering mechanism 19Steering Trim, Electronic 11, 12, 17, 19Steering Wheel 11, 19Storage 45Supplies 6Support 4, 42-43Suspension Arms 7Tank 1 33Tank 2 33Tank 3 33Tank 4 33Tank 5 33Tank 6 33Temperature, see Engine; temperatureTemperature gauge 36

digital temperature gauge 36infrared temperature probe 36

Throttle Arm 22Throttle Neutral Adjustment 11, 16Throttle response 35Throttle slide 35Throttle Trigger 11, 16, 19Throttle Trim, Electronic 11, 12, 16, 19, 35Toe In 39Tools 6TQ, see Radio SystemTransmission 7Transmitter 12, 18, 42

indicator light 19power indicator 11, 13

Traxxas Lifetime Engine Replacement Plan 44Trim, see also Throttle Trim and Steering Trim12Troubleshooting 42-43Turnbuckle 7Water 43Wear-in 25Weather conditions 35Wheels 9Wiring diagram 11WOT 25, 28X-tal see also Crystal 12

Index

Nitro 4-TecOwner’s Manual

Model4810

Traxxas Corporation, 1100 Klein Road, Plano, Texas 75074, Phone: 972.265.8000, Toll-free 1-888-TRAXXASTraxxas U.K., P.O. Box 1128, Winterbourne, Bristol BS17-2SH, England, Phone: 44.117.956.1002

Internet: www.Traxxas.com, www.ReadyToRun.org

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