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  1. #1
    Traxxas Employee captainharlock's Avatar
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    Tuning your TRX Engine

    Want to get the best performance from your engine? Read these articles:

    How To Start and Tune the TRX 2.5/3.3 Racing Engine
    How To Tune the TRX 2.5, 2.5R and 3.3 for Best Performance
    Tuning your Pro .15 or TRX .12 engine



    Edited to add Pro .15 tuning. The TRX 2.5, TRX 2.5R and TRX 3.3 all tune the same way. The Pro .15 and TRX .12 both tune the same way. NC
    Last edited by Double G; 07-26-2012 at 12:05 PM. Reason: Updated links
    Terminal is not the end, only the beginning...

  2. #2
    nightflyer885
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    HP of 2.5

    How many HP does the trx 2.5 have? and is it bigger than a .18 engine?

  3. #3
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    Talking

    im pretty sure the 2.5 cranks out 1 hp
    Edited

  4. #4
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    the trx 2.5 is a .15ci or 2.5cc engine....making it smaller than a .18ci ... but the way these things twist i wouldnt be suprised if it was a powerful as a .18!!! i love mine
    Nitro Ruster: TRX 2.5 engine, RPM wheels, Proline Tires , Graphite Front shock tower , McCoy Plugs , Alum. Shock caps

  5. #5
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    There is an article on the new 2.5 engine( they dyno'd it) in the April 2003 edition of Radio Controled Nitro magazine that says the 2.5cc engine puts out 1.33 BHP @ 30,200rpm and 44.1 oz-in. @ 28,800rpm. They also interview Brent Byers who is one of the designers of the new 2.5 TRX engine.
    BTW They used 20% nitro with 12% lubricant.

    information source was Radio Control Nitro magazine.

  6. #6
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Quote Originally Posted by Kingfish89
    There is an article on the new 2.5 engine( they dyno'd it) in the April 2003 edition of Radio Controled Nitro magazine that says the 2.5cc engine puts out 1.33 BHP @ 30,200rpm and 44.1 oz-in. @ 28,800rpm. They also interview Brent Byers who is one of the designers of the new 2.5 TRX engine.
    BTW They used 20% nitro with 12% lubricant.

    information source was Radio Control Nitro magazine.
    Dyno's are just a reference point. Put the exact same motor on a different dyno and the hp and torque readings will be different. Even if it is made by the same mfr!!! Been there done that with 1:1 engines. That's why Traxxas does not publish hp #s.
    Founder of H.U.A.
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  7. #7
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    would these tuning tips work on other engines as well?? if not where can i get the info on tuning other engines lol

  8. #8
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    This is great help to us newby's out here. Anyone having problems with their smaxx, tmaxx or anything else with a 2.5 should read this article.

    Just what I was looking for!

  9. #9
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    Angry stalling

    I printed and read this article seven or eight times, I have alot of punch for about the first five minutes of running and then my engine stalls. I performed all the recomended tests on the low and high speed settings, I am running at about 250 farenheight but I can only get five minutes or less before it stalls. I also added 15 inches to my pressure line because it seems to be loading up. This did reduce the pressure in the tank and it doesnt bog anymore but I cant seem to fix the stall. Does any one have any suggestions or treatments that I could try? , I traded a thunder quake 1/8 scale for my t-maxx and I dont regret any part of ot, PLEASE HELP to get my 2.5 to stay running, I'm starting to get frustrated

    niro passion to the end.

  10. #10
    ScottShack
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    I have read the article as well as the manual and watched the video several times and still have the same problem. The engine stalls within 5 minutes of starting, always after braking at the end of a high speed pass. I had a similar problem with one of my airplane engines and solved that problem by turning it into a paper weight!

    Give us something new and exciting to fix this problem!

  11. #11
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    I just couldnt take it anymore! I replaced the piston and sleeve and rebuilt and sealed everything between the trany and the fuel tank. I followed the break in to a "T" and on tank #6 i put an o.s. glow plug in. I set the needles back to factory and I almost overhaeted, now im running at 4 1/4 to 4 1/2 hsn and 3/4 out from flush and I havent been hotter than 250 F, I have alot of smoke and plenty of power. I hope I get more than two gallons through it. It stalls once in a while but I ride hard and play wet!
    Last edited by nitro passion; 05-01-2003 at 08:46 PM.

  12. #12
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    Maybe you should email Traxxas itself. I know them to be nice and sympathetic on trouble like this. Good luck and better rides!

  13. #13
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    Wink tuning TRX2.5

    I had problems with my Smaxx, stalling, would not idle, runs good then shut down. Temps in the 240's I set HSN to 4 turns out from bottom, set LSN flush , ran the truck a couple of hard runs after warm up. Started to RICHIN HSN a quarter of a turn at a atime and running hard for several passes, when I got to 4 3/4 turns I had a hard time keeping the front wheels on the ground on grass! I had to lean out the LSN a tad at a time until I had 2-3 seconds of running then idle high then shut down. I also adjusted my throttle return spring more tightly so not to have sticking carb. problem. I can actually run my Smaxx out of fuel( by accident) because it runs so well now. Top end suffersd but I would rather have a starting line grab take off than nothing. I am running Blue Thunder 20%. Ran 5 tanks today and no running problems, hope this helps, cjk

  14. #14
    RC Turnbuckle Jr. arceeguy's Avatar
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    FWIW, I usually tune my engines (any engine, not just the 2.5) with a half tank of fuel. When the tank is full, the engine will run slightly rich - and will progressively lean out a little as the fuel level drops. I find that with this method, the mixture will not get overly lean as the fuel level drops to near empty. I am able to run tank after tank without any stalling or overheating. I'm guessing that most "stalling after 5 minutes" problems can be cured with this method. I also tune my airplane engines with a half tank of fuel for the same reasons. There is nothing worse than having your airplane engine stall when you're lining up for a landing!
    Speed costs money, how fast do you want to go?

  15. #15
    ScottShack
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    Thumbs up It's WORKING!

    Well it took a while but I finally solved my problem with stalling after it's warmed up.

    What I ended up doing was to lean out the low end almost two full turns from flush on the LSN. Idle temp is about 180, it starts like a dream and keeps running for long periods of time. I have plenty of punch off the line and have to watch it to keep the front end on the ground from a dead stop. I have to continually play with the HSN each time I go out. Ambient Air Temp changes really play with the mixture, and going from the low 60's to mid 80's can play havock on your HSN settings.

    I just got back after running the thing for almost two hours straight. I'd still be out there but I lost one of the steering posts playing in the dirt!

    All I have to say, is to stay cool and have lots of patience when your trying to tune it in. Once you get it right, it's AWESOME!!!

    Shack

  16. #16
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    WAIT A MINUtE its a .15!!!!!!!1

    i thoguht the 2.5 was a .21 whut the **** do u mean its not even a .18!!!!!!!!!!!!!!!!
    Give me some info on this one please

  17. #17
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    Re: WAIT A MINUtE its a .15!!!!!!!1

    Originally posted by Maxx2.5 211
    i thoguht the 2.5 was a .21 whut the **** do u mean its not even a .18!!!!!!!!!!!!!!!!
    Give me some info on this one please

    NO NO NO Big difference in piston size between the .15 or 2.5cc and the .21 or 3.5cc engines.

    My theory is that Traxxas made a bunch of chages to the .15 and was almost able to get the performance of a mild big block .21. Now that they had developed such a great small block they wanted to be able give it a class of it's own. Or maybe they're reasoning was they knew that the big block maxx was coming on strong and no one would want a big heavy truck with a little .15 in it. Traxxas made the new engine and instead of scaring you off by calling it a .15, they called it a 2.5 to fool folks into thinking it's a .25. Who knows!!!!

    Don;t get me wrong now....The 2.5 is a GREAT engine, but it's no 8 port hyper, OS RZ .21 or Picco .26 by any means.

    I compare the new 2.5 engine to the power of a Duratrax Torq .21 or a Force P4.

    REMEMBER THAT'S ONLY MY OPINION!!!

  18. #18
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    2.5 is .15

    When traxxas was thinking of a way to ID the new engine,

    Lets think... TRX .15 II
    .......... TRX .15 Two...

    It just makes sense to call it a TRX 2.5 because thats what it is..


    In Europe(Not UK), all engines are called by there metric volume, and not there cubic Inch.

    So whats the difference ...

    2.5 cubic centimeter (metric) is .15 cubic inch (imperial).

    a 2.1cc is a .12
    a 3.5cc is a .21
    a 4.3~5cc is a .26 or .27

    honda civic: a 1500cc (also called a 1.5litre) is a 90ci.

    Chevy 350ci is a 5.7 litre.

    Heres a link to look at,

    http://www.rbproducts.com/rbww/index.htm

    They make the most winning-est 3.5 buggy engines in Europe (I think)
    Last edited by Spellspt; 08-03-2003 at 07:44 AM.

  19. #19
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    I have read that article prolly 10 times now it still wont work what the hecks my problem i have tryed tuning each needle and am now back to factory break in 4 turns out and flush on lsn it runs for a sec then dies.
    go fast live faster bugs wash off . rock chips can be fixed.

  20. #20
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    I have the same problem. I've been trying for maby a month now and I still cant get my 2.5 to work. It always does the same thing. Run good, stall,then die. And then I cant get it to start for 5 minutes. The same thing happens even on factory settings.
    dont fix it until its broke.

  21. #21
    Traxxas Employee Nitro Chicken's Avatar
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    You might need to call us at 1(888)TRAXXAS and see if we can figure it out over the phone!
    Last edited by Nitro Chicken; 04-06-2006 at 10:45 AM.
    "Fortunately son, I says fortunately I keep my feathers numbered for just such an emergency!"
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  22. #22
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    tryedthat

    i called once.Tryed some of the tips, but i think the piston/sleeve needs replacing.
    dont fix it until its broke.

  23. #23
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    Thx for responding guys i have had no luck getting it to run spent the my day off today trying to get it to run... same run fast for 5 minutes stall and takes me a few minutes to get it started again..... i dont have the patience to send it to traxxas so ill prolly spend more money to buy the rebuild kit and start all over again.....they never said it was easy did they? also thx Nitro mabey ill try that b4 i go spend more money
    Last edited by traxxaseye; 08-07-2003 at 01:29 AM.
    go fast live faster bugs wash off . rock chips can be fixed.

  24. #24
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    RE-TRIED all of the factory setting and traxxas directions AGAIN today and it still dies after only a minute or two of running!!! Will restart if you keep the glowplug going after it starts...but dies almost as soon as you remove the igniter!!! Doesn't matter even if ya rev it up and blast off right away, usually dies again the first time I let off the gas!!

    When it runs, it hauls, but usually it runs for very short time and then dies! Spoke with customer service the other day and learned a few more things about glow engines, but none of it helped! Going to take it back to lhs where I bought it and tell them to, "MAKE IT RUN!!!!!!!" Just about had it with this engine.

    BTW my carb sticks sometimes too...tried lube, repeated throttle cycling (full ope, full close, repeat, repeat, etc.) My friend's .15 Pro with many gallons through it runs way more reliably than my new motor even on hot days with old fuel, however not as much power. Gotta run first before worrying about lots of power.

  25. #25
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    2.5 TRX = Paperweight

    I've been thru everything everyone has mentioned in all of the above posts. I am just about to finish my 5th qt of Top Fuel (as Traxxas recommends. I have been able to run a full tank of fuel in my Maxx...start to finish...ONE TIME. Withiut stalling etc. Next tank of fuel (no adjustments in between) ran like poop. Now I notice that when I do my afterrun procedures (after run oil) if I check in 1 hour after doing so, I have a puddle of oild below my flywheel which now means my rear main crank bearing is leaking. I'm calling Traxxas tomorrow for some customer service type action.
    She's Classy...She's Sassy...She's put together like an Austin Healy Chassis with a Tan...Talkin bout Louanne....George Thorogood

  26. #26
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    this has to be the tightest engine I've ever had!!! thank god for this article, I almost took the engine apart to see if something went inside it!!!

    might I also suggest you guys stalling when you're braking, check the idle screw that it's tight so the opening doesn't get smaller (or closes) when you hit the brakes...sometimes the screw is just loose enough for play that can cause this.

    also how old are your trucks, maybe it's that the older engines weren't as good as the one made now????
    Last edited by Evilpete; 10-29-2003 at 12:02 AM.

  27. #27
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    I just got my Sportmaxx for christmass and i broke it in yesterday and at first the engine was kinda touchie and would stall a bit on the first tank but by the third tank it was very difficult to keep the front wheels on the ground so i had to run it in a field to be able to control it. Also i cant wait for my FREE 2-SPEED that comes with my sport-maxx. Otherwise the only thing that i have done to it since X/mass is put an aluminum blue pipe on it!


    READY TO RUN.................READY TO REPAIR IS MORE LIKE IT!!!

  28. #28
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    i agree ! i love the truck,but something has got 2 give with these 2.5 's a recall maybe? tuning it is a pain ,i try an tune mine and think it's all good put the body on and it cuts off ! gotta remove the 4 clips take the body off ! tune again etc. i noticed with the body on plays a role too ,at least in my situation ! my .15 rustler is so reliable i love it 2 death ! My plan now is to put the sirio engine and hopefully it won't be such a pain to tune ! i heard it wasn't! RTR (Repair) LOL! True dat!

  29. #29
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    Smile Finished the 5 tank break in

    But on the sixth tank, i had cutting out on WOT. I have the new TRX 2.5. I tried leaning it out but just the same. Still plenty smoky like so it can't be too lean .. can it?

    The glow plug seemed to be bubbling... i guess that is up the swanny then?
    Then i smashed it into a wall on one of the high speed passes
    It's only plastic i suppose.... the left front wheel went bouncing off like a wheel off a crashed Indy car
    I would think anything would have broken under the circumstances (brick wall)
    upper/lower A arms left bulkhead A arm pins steering plate and servo saver, 2 shock caps. Not bad for a first accident
    Would be nice to get the motor running proper tho. I am gonna read the guide again and have another go at the weekend, after all the new parts have arrived and been in stalled!

  30. #30
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    Your too lean if the engine is cutting out at wide open throttle.
    Almost stock E-Maxx & far from stock 2.5 T-Maxx :)

  31. #31
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    It was on standard break in settings

  32. #32
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    I would richen the HSN up some till it stops sputtering at WOT. Also, the temps your running the truck in is going to make a difference too. Remember Traxxas is in Texas so they set it for that type of climate. If your in the Northern part of the country and trying to run the truck in sub freezing temps then your deffinitly going to need to richen it up. Also what kind of temps is the engine putting out when it starts to cut out at WOT?

    good luck
    Almost stock E-Maxx & far from stock 2.5 T-Maxx :)

  33. #33
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    Air temp must have been about 46 F. The engine was running around 230 - 250 F

  34. #34
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    Been out tuning again today, richened HSN up from 4 turns to 5.5 and seems to run lots better on WOT and top end runs. Although the idle speed and take off were not very responsive. Leaned off the LSN cos it seemed to be bogging and splutteringa bit seemed better just had problems getting the idle speed right. Doing the pinch test it speeded up loads and tried to take off.... seemed to rich low down from what i read on the tuning section. Then the starter battery went flat and i called it a day.

  35. #35
    cooldude3552000
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    Originally posted by =MATT16=
    im pretty sure the 2.5 cranks out 1 hp
    The 2.5 is 2.5 cc, and if it puts out 1hp why does a 25cc leafblower engine barly put out 1hp, and a 43cc scooter engine put out 2.2HP???????

  36. #36
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    Quote Originally Posted by cooldude3552000
    The 2.5 is 2.5 cc, and if it puts out 1hp why does a 25cc leafblower engine barly put out 1hp, and a 43cc scooter engine put out 2.2HP???????
    Lol.

    Because (unless you're a mad man), you're leaf blower does not run on METHANOL with a 10%-30% mixture of NITRO METHANE

    Try your scooter on a alcohol fuel with nitro methane and oil And hang on! Lol
    [Traxxas REVO 3.3]: Tekno wing mount. GH aluminium bits'n'pieces. FOC. Spektrum. 40s Velocity & Bow-Tie

  37. #37
    RC Turnbuckle Jr. tmaxxfreak's Avatar
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    Originally posted by cooldude3552000


    The 2.5 is 2.5 cc, and if it puts out 1hp why does a 25cc leafblower engine barly put out 1hp, and a 43cc scooter engine put out 2.2HP???????
    The 2.5 puts out 1.33hp this from a article in one of the nitro mags..A leaf blower does'nt run at 33,000 rpm. Thats why.
    If you can't fix it. Smash it with a hammer...If that don't work hit it again...
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  38. #38
    cooldude3552000
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    so the leaf blower motor has alot more torque.

  39. #39
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    My Novarossi SBK01 putts out 3 HP, does that mean I can replace my lawnmower engine with it?

    lol


    The leafblower engine has gobbs more torque than a little nitro eninge does. Just because it's rated at 3 hp doesn't mean it has the same torque rating
    Almost stock E-Maxx & far from stock 2.5 T-Maxx :)

  40. #40
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    THATS FUNNY .....ALTHOUGH IT WOULD BE MUCH LIGHTER AND EASIER FOR THE KIDS TO PUSH

    Please do not type in all capital letters. Thank you.
    Last edited by smg323; 08-02-2004 at 08:32 PM.
    Laying the Smack down

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