High Temps...not sure why

[DougJorgie]

I have a Traxxas TMaxx 3.3 and I am having a hard time getting my temps down and also getting a nice smoke trail no matter what I do. I found that my fuel cap was not sealing properly...fixed that and it helped a little. I had my truck out yesterday and couldn't get the temps down to 220-240. I kept making the HSN richer until it was bogging down and wouldnt get the rpms high enough to shift to second. I leaned it out a little from there and it seemed OK other than the smoke trail. The smoke trail is good at lower rpms but it disappears as the rpms go up until it is barely there at high rpms. There was nothing I could do to get more smoke so I moved to tuning the LSN. I have that to 3 seconds on the pinch test. I didnt have to mess with the idle because it was nice and low and it would idle steady without any stalling. So, in theory it sounds like I have this tuned good(other than the smoke trail), right? Here's the problem...when I am running it, it does not come down to a nice idle when I let off the throttle. I have to feather/play with the throttle to get it to come down. At this point when I check the temp it is usually around 270-290. Could the temp be high because the rpms dont come down to an idle when I let off the throttle. So I am thinkin when I am running the engine never slows down to an idle causing the temp to constantly go up. I was also wondering if it could be the Tower Hobbies 20% Nitro fuel I am using. What do you guys think? Keep in mind that when I broke in the engine I could not get it to run consistently, the fuel cap was not sealing and I was and still am using the Tower Hobbies 20% fuel.

 

[Jacks9930]

How new is the motor? One of my older motors with a new piston and sleave had a leaky carb and was running hot at WOT. The carb was lean out at WOT and at an idle everything was fine. I submerged the carb under water covering both ends with my fingers. I blew in the fuel hose and watch the bubbles apper around the slinding shaft. Unfortunetly it was too late for that motor, the block was cracked.

 

[olds97_lss]

Running too tall of gearing for the tires/terrain will also cause it to run hot. Any binding in the drivetrain will also add to the problem.

I usually gear for torque more so than speed with all my rigs. I run in grass 80% of the time, the other 20% is running in a skate park and jumping out of it into the grass. Running lower gearing lets your engine not work as hard, but you have to be mindful of how easy it is to get the rpm's too high with lower gearing or you blow the engine anyway.

 

[DougJorgie]

How new is the motor? One of my older motors with a new piston and sleave had a leaky carb and was running hot at WOT. The carb was lean out at WOT and at an idle everything was fine. I submerged the carb under water covering both ends with my fingers. I blew in the fuel hose and watch the bubbles apper around the slinding shaft. Unfortunetly it was too late for that motor, the block was cracked.

I am 3/4 of a gallon through a brand new Traxxas 3.3 motor. I just got the truck recently.

 

[Mn Monster]

keep in mind that the temp range 220-240 is just that, a range, my 2.5r runs in that range, but the 3.3 on my maxx runs at about 260-280. some motors run hotter than others. tune for performance not by temp. now obviously if it's running over 290-300+ plus on a regular basis than you have some other problems. could be your Lsn is set to lean, or you may have air leaks. can you see air bubbles in the fuel line ?

 

[Rolex]

The fuel cap was not sealing, the idle won't come down right away, you run mostly in the grass and make jumps at skate parks.
A. You have an air leak
B. You have an air leak
C. It's working its hardest
D. It's working its hardest

Deal with the obvious first. Take care of the air leaks.

 

[DougJorgie]

can you see air bubbles in the fuel line ?

Yes, I have seen air bubbles in the fuel line. What does this mean? Is it that there is a leak in the fuel line at the tank sucking air?

 

[Mn Monster]

Yes, I have seen air bubbles in the fuel line. What does this mean? Is it that there is a leak in the fuel line at the tank sucking air?

could be any number of things have you sealed the engine ?

these might help you
how to find air leaks
[ame="http://www.youtube.com/watch?v=tZ3WcPoa1DY&feature=relmfu"]Nitro Engine Air Leak Detection -- Vid 12 How to Tune Series - YouTube[/ame]



how to seal an engine
[ame="http://www.youtube.com/watch?v=rncdYL-PBL4"]How to Seal A Nitro Engine -- Vid 13 How to Tune Series - YouTube[/ame]

 

[3_Stroke_Motor]

270 to 290 is just above what traxxas recommends you stay within. and the disappearing smoke trail at high speeds and RPM is most likely due to the fact that your moving faster and more air volume is blowing the smoke away from the pipe, thus making it dissipate quicker. Your not far from being in a good tune. Where are you taking the temp from? Traxxas says to take it from the top of the glow plug. also, are you taking the temp right after a high speed run? Keep doing that but keep taking the temp after a high speed run to see if your engine gradually cools down after a high rpm run. Replace your fuel as well, I have found when the ethanol evaps from the fuel, you tend to get higher running temps. DONT ALWAYS TUNE BY TEMPS!

 

[Rolex]

DONT ALWAYS TUNE BY TEMPS!

NEVER tune by temps. That's not what gives you the best low and high end performance. It's just a safety measure to make sure you don't burn it out by running too lean.

 

[olds97_lss]

Or wear it out by running too cold.

That said, I still try to keep my temps below between 200 at the lowest and 270 at the highest. Typically I'm in the range of 220-250 almost all the time. I have yet to run an engine that sounded and performed well at more than 270. Usually if it doesn't sound right and isn't putting out the power I expect, the temps reflect that. On occasion though, I've had high temps with an engine that seemed really rich (lots of smoke, loading up really fast, not clearing it's through when opening it up). Usually the culpurit is an air leak somewhere, a bad bearing causing drag, a slippy clutch or a dragging clutch.

Also, a worn out engine with rich settings will tend to run hotter and have tuning issues or flameouts for no reason.

 

[Rolex]

Here it is...

https://www.rcnitrotalk.com/forum/showpost.php?p=726317&postcount=5

 

[mrbones]

1) Seal up your engine.
2) If you run in high grass, you will overheat.
3) Take that temp gun and put it in a drawer somewhere and leave it there.
4) Keep putting fuel in until it starts to bog and then back it off a little and leave it there.
5) Take a look at the tuning chart in the beginning of this forum and follow what it says.