Traxxas Carbs...

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Morpheus

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Ok, So I've had my T Maxx almost a month now, and it's been fun for the most part, but I do have a complaint. It seems to NEVER keep the same tune. Seems like once or twice a week, it's going back into the shop to be re-tuned. The temps (outdoor temps that is) have been pretty consistent the past few weeks, in the mid 60's during the day, however, I can't say the same with my carb settings. Is it just Traxxas carbs that are finicky as hell, or just me? I'll have it running great one day, popping wheelies, spinning tires, etc, and put it up, do my maintenance, and a day or two later, running like crap again!! The shop person kinda hinted around today that Traxxas carbs aren't exactly the best, this true? Are Picco, and OS carbs inter-changable with 2.5?? I just want something that stays consistent, this is just getting old quick. Do I just need to swap motors all together, or can I just change carbs?? Thanks

T,
 
Traxxas engines can be finicky. I'd seal it up and see if that helps. A quick search on here will yield you a ton of info on sealing your engine. It's a breeze to do, even if it's your first time. Just take your time and ask questions.
 
As for an OS carb you can get an 11k carb for it....it's only 80 bucks!! I would seal it up and run it some more then find a decent os/picco/sirio/rb engine of some sort. Os 18tm's are still available on ebay for a decent price, it'll smoke your 3.3. Careful if you decide on something too big it'll tear up your stock driveline.
 
It takes very little ambient weather change to throw off tune. You may just want to work on adjusting the tune yourself.

Regardless of engine or vehicle, I've always had to tweak the tune a bit each day I run and occasionally throughout the day as weather changes or places I bash change. LIke if I run at the skate park, I tune for a rich bottom end because I rarely hit 3/4 throttle. But if I'm tooling around a park, I spend a lot of time at WOT, so I run a richer top end. Or, if one park was mowed recently and the other wasn't, the taller grass causes more drag, so I run richer in general to compensate.
 
It takes very little ambient weather change to throw off tune. You may just want to work on adjusting the tune yourself.

Regardless of engine or vehicle, I've always had to tweak the tune a bit each day I run and occasionally throughout the day as weather changes or places I bash change. LIke if I run at the skate park, I tune for a rich bottom end because I rarely hit 3/4 throttle. But if I'm tooling around a park, I spend a lot of time at WOT, so I run a richer top end. Or, if one park was mowed recently and the other wasn't, the taller grass causes more drag, so I run richer in general to compensate.

well now i see why you got Nitro Guru of the year. . .lol. . .good info man
 
So when you tune it for various parks, grass, weather ect, are you tuning the LSN or low speed needle, or both?

T.
 
So when you tune it for various parks, grass, weather ect, are you tuning the LSN or low speed needle, or both?

T.

Both.
Tall grass, a bit rich on both.
Lots of WOT running, rich on both, but more so the HSN.
Mostly short runs with typical max of 1/2-3/4 throttle, rich on LSN.

Usually, adjustments made to the HSN affect the LSN anyway in the same direction. Adjusting the HSN changes the overall fuel flow to the engine. The LSN is there to fine tune what it does from idle to about 1/4 throttle. From 1/4 on up, it's the carb venturi/slide bar doing the metering creating extra suction pulling fuel into the engine and the HSN limits how much or how little fuel is allowed in.

The pipe you run plays a part as well in both tank pressure and engine pressure. If you run a very free flowing pipe, you don't get as much pressure into the tank shoving fuel into your engine. So you generally have to tune more rich to compensate, but get good low end power as a result. A more restrictive pipe usually causes more tank pressure which lets you lean it out mechanically via the needles to compensate.

The exhaust pressure wave is another thing the pipe controls. It's similar to how valves work in a normal engine, except it's air pressure caused by the shape/design of the pipe. Some pipes are designed to create a pressure wave that promotes higher RPM running, others low end and others in the middle. Typically referred to as "tuned" pipes.

Here's a couple articles on tuned pipes if you care to read a bit:
Tuned Pipe
Tuned Pipe

There's a lot of info out there and I'm by no means an expert. Just trial and error that some times end with days where I can't get a single thing to run "just right". I hate those days!
 
ok, cool! So when the truck is sluggish on take off, then I need to adjust the LSN to make it a little more rich then?? And if I'm making more high speed runs, and its a little sluggish, then I need to make it a tad more rich on the HSN?? So when you make adjustments on the HSN, then you need to make an adjustment on the LSN as well?? Thanks

T.
 
Sluggish on takeoff is probably too rich to begin with, you'll want to turn it clockwise (to the right) to lean it some. Try 1/8 to 1/4 turns until it takes off strong, and then let it be. :)

Same with the HSN: if it seems to have really good power but gets too hot or cuts out at the very top of the RPM range, it's probably running a bit too lean. If it is sluggish, and the back tire is getting wet because of unburnt fuel coming out the pipe, THEN it's running too rich, and will like to be leaned a tad. :)
 
Ok, So I've had my T Maxx almost a month now, and it's been fun for the most part, but I do have a complaint. It seems to NEVER keep the same tune. Seems like once or twice a week, it's going back into the shop to be re-tuned. The temps (outdoor temps that is) have been pretty consistent the past few weeks, in the mid 60's during the day, however, I can't say the same with my carb settings. Is it just Traxxas carbs that are finicky as hell, or just me? I'll have it running great one day, popping wheelies, spinning tires, etc, and put it up, do my maintenance, and a day or two later, running like crap again!! The shop person kinda hinted around today that Traxxas carbs aren't exactly the best, this true? Are Picco, and OS carbs inter-changable with 2.5?? I just want something that stays consistent, this is just getting old quick. Do I just need to swap motors all together, or can I just change carbs?? Thanks

T,


Seal it and get a carb from an OS 18TM, I believe it's an 11K. It's not cheap.
 
i put one on my t-maxx, it was like putting a good engine in, bolt on NO mods needed. you need some numbers 21982000 carb 11k 18tz/21tm i bought 3 for $88 each from tower hobbies. those numbers are straight off the invoice.
 
Look, OS makes great products, but 80 bucks for a carb?! Thats more than my entire picco cost....

Although my buddys os18 would probably sit there and idle for 2 hours if you let it, so I guess you get what you pay for....
 
2 best cures for a picky Traxxas mill, well 3 things. A Motorsaver air filter, THS pipe and a M2C medium 2 shoe clutch kit with 1.0 springs. Night and day difference. You still have to tweak it all day long but it responds so much better, runs cooler and the clutch hits like a 1/8th scale clutch, perfect. No wheels turning at idle either. Takes all the guess work out of the equation.
Next best thing, O.S. 21 TM. The most user friendly engine I have ever owned.
 
yep 88 is a lot for a carb. i have to say i dont have a lot of time on it, but it acts so much better than a traxxas carb. diff people talk about metal carbs vs plastic carbs. of course the os carb is metal. i like it so much that when my jato starts acting up the first thing ill do is put the 11k on.
 
With the os carb in 3.3 what would be best setting for it?
Just use the settings from whatever OS engine it comes off of and start there. I think the OS 11K carb has HSN flush with the top of the brass collar, LSN flush with the throttle arm and the mid-speed (low speed needle seat) is .5 turns from flush, then left alone. Then adjust the HSN/LSN in 1/4 turn increments once warmed up until it's running how you want.
 

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