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  1. #1
    Registered User OneBigMan647's Avatar
    Join Date
    May 2002
    Calabasas, CA

    The Nitro 4-tec Made Simple

    Now, i've noticed there are more newcomers than ever on this board, and i'd like to answer ALL your questions once and for all so you will never ask the same question again. You might say, dang, this is way too long, im not readin it, but i will gaurentee you will learn alot more if you read this. Admins, if you find this article good enough to be a sticky, please make it one.

    So let's start with the basic specs of the 4-tec.

    -The nitro 4-tec is a 1/10th scale, gas-powered touring car.
    -It takes 200mm size bodies. 190mm size bodies will also fit, but the tires WILL stick out a little bit, and there will be a good chance that the
    body's wheel wells will rub against the tires.
    -The 4-tec can take any 1/10th scale wheel. All from the standard size rims to super-size rims, any brand also.
    -The tire width the 4-tec takes is 24mm-26mm for rubber
    tires on 26mm rims. For foams, you can fit from 26mm-32mm.
    -The 4-tec can accept any engine ranging from .12-.18 size without modifications.
    -The 4-tec can take any electronic setup made for cars. Every
    combination ranging from 3-channel fm to 2-channel am. You can use any servo for any reciever, just make sure that you've got the rightconnector for the reciever.
    -The 4-tec takes a centrifugal clutch, and all clutches will not fit. If youare looking to put buy a new clutch, make sure it is made for the 4-tec and not any other car. The only other car that might take the same clutch are other traxxas cars such as the nitro rustler or maybethe T-Maxx.
    -The nitro 4-tec's fuel tank is 75cc's large. It is possible to put a largerfuel tank, i've seen someone put in a 100cc tank. But it is not worth it, it will probably mess up the car's center of gravity and won't be a big improvement.
    -The 4-tec can take any fuel made for CAR engines. As long as the fuel has at least 18% oil content and 10% nitro, the fuel will work fine.Remember, this is only for trx racing engines.
    -The intake is a basic part and IMPORTANT part of the 4-tec. Any
    intake will fit the trx racing engine, just make sure it's made for yourengine's size.(ie .12, .15)
    -The nitro 4-tec has a 2-speed clutch type transmission. Look in yourowner's manual to figure out how to adjust this.
    -The drivetrain of the nitro 4-tec rtr is 4WD belt drive. It has 2 gear diffs front and back.
    -You can adjust camber,toe-in,shock positions, change swaybar
    positions, and differentiate between shock oils and springs.

    Now that we have covered the basics of the 4-tec, it's time to learn how to maintain this beast..

    -After your done running your car for the day, you must put after run oil in your engine so it does not rust from the leftover fuel, which will
    attract moisture and create water, which will rust the innards of the
    engine. You should put 3-8 drops of after run oil into the carb.'s
    opening or take out the glow plug and drop it oil right into the engine.
    After you have put the after run oil, rotate the engine a couple of timesto spread the after run oil all throughout the engine.
    -Diffs, if you have a rtr 4-tec, you have gear diffs, which need
    absolubtely NO maintenance at all. If you have a nitro 4-tec PRO, youhave pro ball differentials(basically limited slip differentials), you mustclean take these apart and regrease them as soon as they start
    becoming gritty when turning. Use the grease that came with your pro kit.
    -Cleaning, it's good to clean your car after anyday you run it. It will keep everything shiny () and keep the car rolling smoothly. It will help the car's rotating parts work better and more freely. You can use many different types of cleaners on your car. Just make sure they won't harm the car. Most people use air compressors, denatured alcohol, and specially made r/c car cleaners.

    That's pretty much the basic maintenance this car needs.Now, let's talk about how to tune the engine and all the rights and wrong for this car.

    -The basics of tuning: There are 3 tuning needles on your carb. Thehigh-speed needle(hsn), the low-speed needle(lsn), and
    the idle speed needle(isn).To tune the engine for performance, you only adjust the hsn, and lsn. Once you have adjusted the isn to idleyour car perfectly, you never touch that again. To richen the engine, you turn the needle counter-clockwise, the lean it, turn it clockwise.These is how you tune for both hsn and lsn needles.
    -To check temperature, you can use a temperature gun, but if you donot have one, you can do the "spit test." You basically spit on the cooling head, if the spit boils away in less than 3 seconds, than yourrunning too hot.
    -Some symptoms of a lean engine are: Engine cutting off at high
    speeds, smoke coming from the cooling head, engine makes a
    "detonation" sound when de-accelerating, and no smoke coming from the exhaust at highspeeds.
    -Some symptoms of a rich engine are: Stalling when accelerating off the line, excess fuel and smoke coming from the exhaust,engine shutting off when shifting into second gear, and engine constantly getting flooded when trying to start.
    -When you start to tune your engine, turn in very small amounts.
    These needles are sensitive. You should turn in 1/16th turns. Very slowly until the engine is running good.
    -There is a way to tell if your engine is running to rich or too lean
    besides the way i stated above. You can "read" the glow plug.
    Basically, you take out the glow plug, and look at the bottom of it. If itis wet and a dark color, then it's too rich. If it's brown and dry, it's toolean, and if it's tuned good, it will be the natural color of the glow plug. You can only read silver or any other light-colored glow plugs. Some
    glow plugs are black and you cannot tell how your engine is running.

    Those are the basics of engine tuning. Now, were going to figure out how this beast of a car works, inside to out.

    -The car is powered by the engine, so let's figure out how that works. Theengine has many parts. The crankshaft,piston,sleeve,connecting rod,
    carburator, backplate, bearings, cooling head, crankcase, and the glowplug. Those are the parts of a two-stroke engine, this is how it works.
    -Fuel comes into the carb and the carb adjusts the fuel/air mixture going into the engine. After the fuel has gone into the carb, it heads downinto the crankshaft, directly from the crankshaft, it goes into the
    crankcase. Then, the crankcase has fuel in it, so as the piston goes down,
    the fuel goes into the top of the crankcase, the explosion chamber,so when the piston goes up, the glow plug will ignite the fuel and pushthe piston back down, causing the crankshaft to turn, this rotation happens many times per second. After the piston goes down after theexplosion, the exhaust will go into the header then the pipe, if any un-burned fuel goes into the pipe, the pipe's backpressure will take thatfuel and put it back into the engine. This is why 2-stroke engines aren't
    very fuel efficient. 4-stroke engines have more of a complicated process,4-stroke will be alot more efficient, but im not going to get into 4-stroke.

    That's how an engine works, so let's figure out how the drivetrain and transmission works...

    -Let's start at what engages the car to move. The clutch. The nitro 4-tecuses a centrifugal type clutch. The clutch is held together by extremelystiff springs, so as the engine rotates, the spring will expand and let the clutch hit the inside clutch bell, causing the car to move. It's a very simple design.(NOTE: Clutch's should be replaced once a year or so)
    -So after the clutch engages the clutch bell, it will turn the transmission.
    The 2-speed mechanism works just like the clutch. As the spring expands,it'll hit the 2nd gear, then engage the 2nd gear and leave the 1st gear alone. (NOTE: When you adjust the shifting point, you are basicallyadjusting the stiffness of the spring, so anytime you forget which way you turn to make it shift later, remember this, if i turn it clockwise, i am screwing the spring IN, so i am making the spring stiffer, thus makingthe 2-speed shift later)
    -We got through the 2-speed, now, the power evenly spreads to the frontand rear of the car thanks to the 4wd belt drive. After the belts spin, it hits the differentials, this is an important part on the handling of the car.
    -There are two types of differentials, gear differentials and limited slip differentials. I will explain the gear differentials first.
    -When you get power to the gear diffs, it will adjust the power to the leftor right wheel. Say you are making a left turn and pushing the gas, the gear diff will give more power to the wheel that's spinning more, which will be the inside of the wheel. So the inside wheel(the left side when making a left turn) will be spinning more than the outside.
    -A pro ball differential(or limited slip differential(lsd)) will make the car handle MUCH better. Let's say were making a left turn again, once again, the inside will tires will be spinning more than the outside, so what the lsd does is give all the power that's being lost by tire spin on the inside tire, to the outside tire. Causing the car to have much greater traction and be more direct.(NOTE: Look in the manual of your nitro 4-tec PRO to see to adjust a lsd)
    -After it goes to the diff it hit's the driveshaft, which will directly go to thewheels and make the car move.

    Now you get how the nitro 4-tec works MECHANICALLY. Now, we will learn
    about what the parts of the 4-tec are made up of.

    -There are 3 types of parts available for the 4-tec. Aluminum, plastic, and graphite.

    -PLASTIC: This is what the car comes with. Plastic is heavier than graphitebut lighter than aluminum. Plastic has pretty good strength, strength levelis in the middle, aluminum being stronger, graphite weaker. Plus, plasticcan bend to a certain point without breaking, and of course will bend back to it's original shape. Plus plastic is very cheap, there usually won't be a part over 5 bucks that's made out of plastic.

    -ALUMINUM: The shiny stuff. Aluminum has it's pro's and con's.
    Aluminum is the strongest of the three but also the most weight and money. ALuminum parts usually range around $22. Once aluminum bends, you cannot bend it back, unless the part is flat(ie rear shock tower) and you have a vice. People usually buy aluminum for strength and show.

    -Graphite: These are what the racers use for chassis flex and saving weight. Graphite is the most brittle but has very little flex. It is the lightestof the three and the cost range is between plastic and aluminum. Graphite parts usually won't break because they're used for parts that usually do not hit curbs or anything. They are used for flat parts such as the rear shocktower, upper chassis, front tie-bar, brake disc, and rear brace. This will
    take almost all chassis flex out, a stock 4-tec barely has chassis flex, graphite nearly eliminates ALL chassis flex. Chassis flex is how the car will bend left and right or up and down but bend back to shape. You want tohave the least possible amount of chassis flex to have a more controlled car.

    In my opinion: Graphite and plastic. Aluminum is way too expensive, and once you bend a part, you lose 11 bucks. Plastic is the way to go for me.
    It's cheap, strong enough(for me at least) and it's light. I use all the graphite parts since i have a nitro 4-tec PRO. So basically, my advice, stick with plastic parts and get all the graphite parts.

    There are titanium parts and some "graphite" parts(losi's graphite editions), but those are not available for the 4-tec.

    Weve almost covered the entire car, now for the good stuff, what YOUneed to know for racing.;D(my favorite part :chuckle

    -CAMBER: Camber is the angle positioned on the wheels. You want negative camber all around on road, if you run oval, then it's a different story. You want 2 degrees negative in the rear, and 1 degree in the front.The whole point of camber is to get all the tire on the ground during a turn. So when your turning in the sweeper after going 40mph on the straight, when you turn, the tire will shift, so all the outside tires will be on the track getting the maximum traction.
    -TOE-IN: Toe-in is the angle on the front of the tires turning in. The rear is not adjustble(by turnbuckle) you can change the stub axle carriers foreither 1.5 degree's toe-in, or 0 toe. You can have toe-in or toe-out. For the front, it matters on your driving style.(I like to have no toe at all in the front, 1.5 in the rear)
    -Chassis Height: If your racing, and your track is fairly smooth, you want to be riding around 3-5mm high max. If your track is bumpy, it's ok to ride at 8mm or so. Basically, you want to go as low as you can without hitting the ground. To adjust chassis height, you put spacers in the shocks to lift the car. You can also adjust shocks positions for height.

    There are more adjustments, such as length, width,ackerman, and such but those are not adjustable on the 4-tec. RPM sells tools for adjusting allthe things i stated above^^.
    -SHOCKS: Shocks are the main part of your car. Without them the car can't stand. Shocks need lot's of maintenance if you want them to run smooth and perform at their max. You should clean your shocks and re-oil them anytime they sound like they have air in them.(if they have air in them, they should make a "squishy" sound when compressing them) When you re-do your shocks, you want to make sure there is no air in them, and they all rebound at the same rate. There are 3 things you can adjust on
    your shocks, the shock oil weight, spring stiffness, and shock piston. Most people use around 50wt oil all around, 3-hole in the back, and 2-hole in the front. You can buy spring sets for your shocks. (My setup is 50wt in the rear, 60wt. in front,3-hole in the rear, 2-hole in the front, 25lb springs in the rear, and 30lb springs in the front)


  2. #2
    Registered User OneBigMan647's Avatar
    Join Date
    May 2002
    Calabasas, CA

    -SWAYBARS: Swaybars aren't too big of a deal. I wouldn't even
    recommend using them if you have gear differentials. You can adjust them by putting them in different positions on the a-arm. If you have gear diffs, only put the swaybar in the front,because if you use them in the rear, you will only lose traction because a gear diff can't control the car as well as an lsd. If you have a lsd's, you can use it for front and rear. (I personally don't use them and i find it better without
    -Tires: There are 2 types of tires, rubber and foam. For rubber, you can have threaded tires or slick tires. For bashing, i would recommend threaded tires, for racing slick tires. I use slick tires for practice at the track, threaded for bashing, and foams for raceday. Then there are inserts for rubber tires. I would highly recommend you to use hpi pro molded inserts, i wouldn't use the inserts that tires come with, those are just strips of foam. Hpi pro molded inserts are a mixture of foam and rubber and make your tires perform to they're best.
    Foams do not require inserts and most are pre-mounted on wheels. Use foams only on CLEAN surfaces, if you use them in dirty or rocky streets, they won't grip or just chunk pieces. Foams last pretty long that is, it matters what softness your foams are. So only use foams if your racing on a track.

    Weve talked about the basics you need to know if you want to start racing. So let's talk about the parts that make these things MOVE!!!

    -PIPE/HEADER: Pipes can be made for top-end power, low-end power,backpressure, or just plain speed thoughout the power range. Pipes are a crucial part and they consider how your engine acts and how your car sounds. The header is also an important part. You want to a have a header in a large diameter and the port fitting the crankcase port perfectly, so itisn't restricting any fuel or smoke to go throught the header. (i use a paris
    turbo ring pipe and traxxas blue header, the pipe is awesome and the header has a BIG diameter)
    -Engine, many people say,"man, i want the FASTEST engine." But, once you get more into the hobby, your not going to be as concerned about speed, you'll just think about handling, because pretty much any nitro car with a 2-speed has plenty of power. You can use .12-.18 engines for the 4-tec. I would recommend you to just stick with your current engine, only buy a new engine if your current engine is gone or there is a REALLY good
    deal on a good engine. The 2.5 has LOTS of power and that's pretty much the fastest .15 there is. So don't get too concerned with engines.(i run a .12 picco, it is very reliable,holds it's tune, and has plenty of power)
    -GEARING: I would recommend you to use the optional gears. They are awesome for tight tracks, and they have a good top end for large tracks.I would not recommend using stock gearing for racing.At ALL, it's just too tall. If your bashing, and you want some FAST acceleration off the line, then getting the optional gearing will improve speed like no other hop-up,
    plus it's cheap, a little bit of a pain to put on but all worth it.

    Alrighty!!! I hope this article has improved your knowledge. THis article is all about the nitro 4-tec. If you have any questions about this article,feel free to pm me or talk to me on aim( my name is mr 3bub1es )or if you have a question that isn't in the article feel free to ask. I will be making an articles all about different brands, parts, my opinions on them, and i will be making another article that tells you how to install/assemble any hop-up
    you buy, all these articles are made to help you, and i spend lot's of time on these so please put them to use. GO TRAXXAS!!!

  3. #3
    Marshal BobR's Avatar
    Join Date
    Apr 2001
    Asheville, NC

    Thumbs up

    Stickified, at least for a while! I guess this has become an unofficial FAQ thread. So, if you've got any tips pertaining to the N4-Tec, post 'em here...
    Last edited by BobR; 11-10-2003 at 11:36 PM.
    Six in a row makes it go.

  4. #4
    Registered User
    Join Date
    Oct 2002
    cheyenne wy
    good info..........lots of info.....but one thing.......on the old rtrs with the pro 15 u do have to do some minor mods to get the slide carb in.......mainly cutting the plastic lip around the back of the fuel the slide carb can open........for the 2.5 i don't know if u have to do that but other slide carbs u do.........just thought i would add that

  5. #5
    RC Turnbuckle Jr. NitroRCracer's Avatar
    Join Date
    Nov 2002
    Adelaide, South Australia
    a bit more info on tyres:

    tyres make one of the biggest handling differences to ANY vehicle.
    a bad tyre choice will give u a bad handling car, and you will be forever trying to "dial in" the rest of your suspension to get them to work..

    if you made a bad tyre choice theres one simple fix .. take your tyres in your right hand, throw them over your left shoulder, and go buy some decent ones, It will save you a lot of time, and probably a few crashes aswell.

    for rough or dirty roads, or for those who want to just bash + expect good tyre life then most ppl recomend HPI X-Pattern **BELTED** tyres with
    HPI Moulded GREEN Inserts fitted to any standard 26mm touring car rims, for examplethese cool lookin' black stock car rims.

    "shore" is the compound of the tyre, higher "shore" rating is a harder tyre with a longer life, and a little bit less grip, while lower number is a softer tyre which will wear fast, but give good grip.
    ALSO -->> front foam tyres ARE NOT the same are rear foam tyres, they have a different mix of foam + rubber.
    Usually you would run a lower shore (softer) tyre on the rear, to help prevent the rear sliding out easily.

    i would recomend anyone wanting foams, to start off with something like these jaco nitro shoes on the front, with EITHER these jaco 2 degree rear offset foams or these jaco 0 degree offset foams
    Last edited by NitroRCracer; 11-20-2003 at 12:29 AM.
    Im no expert. i just play one on the TRX forums

  6. #6
    RC Turnbuckle Jr. NitroRCracer's Avatar
    Join Date
    Nov 2002
    Adelaide, South Australia

    offset wheels give your car a wider stance, while no offset will give your car a shorter stance (wheels closer to the chassis)

    wider offset wheels (like 2mm offset) give the car a wider stance. this makes the car less likely to traction roll, but will allow the rear end to slide a little more..

    narrow offset (or 0mm offset) wheels will give less stance, making the car more likely to traction roll, but the rear end will not slide out as easily..

    Also, a higher offset wheel is more likely to stick out past the body.
    Im no expert. i just play one on the TRX forums

  7. #7
    RC poster
    Join Date
    Apr 2006

    Need step by step instructions

    Are there any posted step by step instructions on the 4-Tec? The owners manual is a little sparce on details like replacing the front drive belt.