Needle tuning, need somebody advice.

[StevenMax]

Hey everyone what’s up!
Been out driving alllll day had a blast. Anyways, I’m having a little bit of trouble with tuning. I have a Traxxas T-MAXX 3.3 with a LOSI 3.4 carburetor on it. The new carburetor makes the truck run unbelievably good so much better and it’s a direct drop in I’m glad I did it. With that being said, no matter what I do the engine seems to run hot. If I richen it up it starts bogging down and running pretty crappy with lower RPM and loss of power it will be around 250°. If I lean it out and get good performance like wheelies, 48 mph top speed passes etc, it runs hot, 300-330. Granted today it was 88 out and Hot, but, Even with the body off it shouldn’t run that hot. It idles great and doesn’t really stall out unless I land hard off of a jump or go from full throttle to break and then it occasionally shuts off so I’m pretty sure the low end is pretty good but I could be wrong.

Looking for advice because some places I see say the Traxxas 3.3 just runs that hot and I cannot get it to run at anything under 300 without it running bad. Some people say the temperature is way too high other say that those temps are normal for that engine, but seems too hot. Thank you in advance for any advice!

 

[olds97_lss]

Well... like you said, there are schools of thought on that... but with fuels having synthetic and castor blends in them these days, the oil in it can handle higher temps safely.

I tend to try and tune so it performs well, runs ok, idles, starts, etc. I check the temp so I know where it is when it seems to be running best. Typically it's in between 240F and 275F. After a few wot long passes, it could edge up to 280F, but usually not.

300F+ does sound high, but if it's running well, putting out good smoke and not blowing glow plugs constantly, see how it goes. Running in high temp/high humidity doesn't help things either. Check your driveline, make sure everything is spinning nice and free.

What fuel are you running?
What glow plug?
Running on grass, dirt or pavement?

For a LSN check, try the following:
Get it warmed up, do a WOT pass, bring it back and have it idle for 5 -10 seconds, then pinch the fuel line until it shuts off.
If it runs a bit, then dies without the RPM's ramping up, it's probably spot on for LSN.
If it dies immediately, it's likely lean.
If it takes a while and slowly ramps up RPM's until it dies, it's likely rich.

Give this a read. Whenever I'm about to run nitro after not doing so for a while, I skim through this as a reminder:

Ron Paris Tuning Tips

I forget half of it, then fight with the engine, or things go well and I don't... lol!

 

[StevenMax]

Well... like you said, there are schools of thought on that... but with fuels having synthetic and castor blends in them these days, the oil in it can handle higher temps safely.

I tend to try and tune so it performs well, runs ok, idles, starts, etc. I check the temp so I know where it is when it seems to be running best. Typically it's in between 240F and 275F. After a few wot long passes, it could edge up to 280F, but usually not.

300F+ does sound high, but if it's running well, putting out good smoke and not blowing glow plugs constantly, see how it goes. Running in high temp/high humidity doesn't help things either. Check your driveline, make sure everything is spinning nice and free.

What fuel are you running?
What glow plug?
Running on grass, dirt or pavement?

For a LSN check, try the following:
Get it warmed up, do a WOT pass, bring it back and have it idle for 5 -10 seconds, then pinch the fuel line until it shuts off.
If it runs a bit, then dies without the RPM's ramping up, it's probably spot on for LSN.
If it dies immediately, it's likely lean.
If it takes a while and slowly ramps up RPM's until it dies, it's likely rich.

Give this a read. Whenever I'm about to run nitro after not doing so for a while, I skim through this as a reminder:

Ron Paris Tuning Tips

I forget half of it, then fight with the engine, or things go well and I don't... lol!

I am running traxxas 20% nitro, which is known to have a higher oil content.
Traxxas medium plug
I do see smoke coming out and that lovely burnt nitro smell
I’m running on hard dusty dirt, a little track with some jumps. You know the kind where you floor it hit the jump land then turn around and do it again lol.
I pinch the fuel line and count, it lasts about 3 seconds revs up slightly then cuts off.
When I rich enough the HSN any more it loses power, bogs, shits off etc and I’ll see unburbt fuel dripping out of the exhaust after a minute if running. Lean it out a little, then it gets better and better until it’s doing wheelies and shifting in to second etc.

All seems great until I look at traxxas link and see 326!

 

[olds97_lss]

Got a temp gun to double check it?

 

[StevenMax]

Got a temp gun to double check it?

Unfortunately no but I will get one. The sensor isn’t accurate with pretty much matching ambient temps and all but I’m gonna go over the motorband make sure everything’s tight, thinking of it i pulled my exhaust off and pushed it back on, there are zip ties on the coupler but it still slides on and off the manifold, it’s possible that’s born putting 100% pressure on the fuel line and causing it to run lean.

It basically gets hotter as the fuel runs out it seems, but I just attributed that to the fact it had been been hitting plenty of WOT during the time it took to run through the tank.

 

[olds97_lss]

What truck is it? You mentioned the engine, but not the truck.

 

[StevenMax]

What truck is it? You mentioned the engine, but not the truck.

T maxx 3.3.
I just got in from running, I cut the windshield out and drilled some holes in the grill. I got the low speed set good it idles pretty nice. I found out this Losi carb responds a lot to super small adjustments, like a 32nd if a turn. I dialed it in low speed and high speed, it’s running right about 250-270 depending on conditions. It leans out after half a tank and seems to gain slight performance but I think that’s normal for a nitro.

It seems a little inconsistent though. One pass it will shift in to second and scream then another it revs almost to shift then falls flat. I assume it’s just a but but rich and can’t wind out high enough. However temps suggest any leaner and I’ll be heating up over 270. Can the low speed being slightly out have an effect on WOT high speed?

It’s so close to being perfectly tuned!

 

[cbaker65]

T maxx 3.3.
I just got in from running, I cut the windshield out and drilled some holes in the grill. I got the low speed set good it idles pretty nice. I found out this Losi carb responds a lot to super small adjustments, like a 32nd if a turn. I dialed it in low speed and high speed, it’s running right about 250-270 depending on conditions. It leans out after half a tank and seems to gain slight performance but I think that’s normal for a nitro.

It seems a little inconsistent though. One pass it will shift in to second and scream then another it revs almost to shift then falls flat. I assume it’s just a but but rich and can’t wind out high enough. However temps suggest any leaner and I’ll be heating up over 270. Can the low speed being slightly out have an effect on WOT high speed?

It’s so close to being perfectly tuned!

Just because it is not quite there on the shifting ,or it is hit & miss shifting ,I would not go any further on the carb settings with
out having any room for error on a lean incident!
You should consider adjusting the shift point from the tranny!...

 

[StevenMax]

Just because it is not quite there on the shifting ,or it is hit & miss shifting ,I would not go any further on the carb settings with
out having any room for error on a lean incident!
You should consider adjusting the shift point from the tranny!...

That’s a good thought, I never messed with the shifting because it works great on the road. I should mention I’m driving on slipper hard packed dirt conditions, mostly flat.
It seems it I made it shift earlier it would be shifting and bogging it down but might help me.

 

[alfredwong2003]

If you rich it out a bit, you will have to close the slow speed needle a bit, may be 1/8 to 1/4, so you will have less unburned fuel, so, it will not be loaded.

 

[olds97_lss]

The way the t-maxx tank is shaped tends to cause the last 1/4-1/5th of a tank to lean out a bit. So that power surge at the end is pretty normal, but not really anything to worry about.

I used to break t-maxx tanks constantly and ended up fitting an OFNA rectangular tank that was uniform in shape from top to bottom. They didn't have that leaning issue as they emptied. They are hard to find now with OFNA no longer existing.

 

[StevenMax]

If you rich it out a bit, you will have to close the slow speed needle a bit, may be 1/8 to 1/4, so you will have less unburned fuel, so, it will not be loaded.

If I richenit any more, the temps def go down, but performance falls off to the point where it’s been held floored and won’t go over 24000rpm or so and won’t shift. That is why the last bit of the tank leaving out causes better performance. But these things steve so good at being out of tune and allowing you to compensate lol.

So you’re saying richen the high speed needle a bit and be lean the low speed? I don’t think it’s loading up it will sit there and idle steady until I shut it off.

 

[Tunedfrog]

Just a suggestion, you could poke a few holes front and back and get a little bit of air flow through the body.

 

[StevenMax]

Just a suggestion, you could poke a few holes front and back and get a little bit of air flow through the body.

The entire passenger side of my windshield is cut out, the driver side is full of holes drilled and I drilled out the grill in the lower portion of the body so it has pretty good flow

 

[alfredwong2003]

The way the t-maxx tank is shaped tends to cause the last 1/4-1/5th of a tank to lean out a bit. So that power surge at the end is pretty normal, but not really anything to worry about.

I used to break t-maxx tanks constantly and ended up fitting an OFNA rectangular tank that was uniform in shape from top to bottom. They didn't have that leaning issue as they emptied. They are hard to find now with OFNA no longer existing.

Hobao own OFNA, so you can still get OFNA parts.

 

[alfredwong2003]

If I richenit any more, the temps def go down, but performance falls off to the point where it’s been held floored and won’t go over 24000rpm or so and won’t shift. That is why the last bit of the tank leaving out causes better performance. But these things steve so good at being out of tune and allowing you to compensate lol.

So you’re saying richen the high speed needle a bit and be lean the low speed? I don’t think it’s loading up it will sit there and idle steady until I shut it off.

Lean out the low speed, will give less fuel to the engine, in a low speed environment/idle, the engine does not need too much fuel, if there are too much fuel, it will become loaded.

 

[StevenMax]

OK tell me how it sounds, still doesn’t sound right to me but it idles fine and never stalls, even if it sits there’s for a few mins. It does grab second sometimes, it does do a wheelie, sometimes, but I’m also in slippery dusty dirt. Temps started out good, about 250, but still go high like 275 then went to 313 by end of tank.

I thought this clip may help for more trained ears.

 

[StevenMax]

 

[alfredwong2003]

As D3MON was saying in this thread 'Can i use VP 25 in a traxxas jato', you may want to try a different fuel with less oil content. Your video did not show it is loaded.

 

[olds97_lss]

Hobao own OFNA, so you can still get OFNA parts.

Yeah, some, but none of the old rectangular tanks I used to buy.