Richened from factory tune but temps still soaring...

Welcome to RCTalk

Come join other RC enthusiasts! You'll be able to discuss, share and private message with other members of our community.

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.

Supra1988T

RC Newbie
Messages
14
Reaction score
0
RC Driving Style
I bought a Traxxas Revo 3.3 and as I completed the break in I smashed into a tree at full throttle. New RPM control arms, steel cv shafts, a slipper clutch, Motorsaver air filter and a failsafe later and its back up and running. I bought a venom failsafe with the temperature monitoring for added protection. I installed the temp probe on the base of the head, 180 degrees from the exhaust port just as described in the manual. Now as the engine heats up the venom shows a much higher temperature than the IR heat gun does at the top of the head, which is to be expected but the peak temp is unnerving.

I had set the failsafe to reduce throttle to 20% if temps reached 302F. Well it hit 302 pretty fast and when I hit the head with the IR gun it only read 265F. The engine was still on the factory tune, blowing smoke and sounded good so I raised the max temp on the failsafe to 340F. Started bashing again and within a few minutes it was cutting throttle again. I drove the truck back over and checked with the gun and got a reading of 310F. The truck seems to be running great and feel like it could be leaned out more, its still blowing smoke. But I'm scared of those temps so I richen up the HSN. Temps are still high and now it feels like its too low on power. Its so rich that its dripping fuel from the exhaust. I've never heard detonation except maybe once on deceleration. Everyone is going to say check for air leaks but its not running lean IMO. It still hasn't burned up the factory glow plug yet either. Ambient air was 55-65F today.

Should I just try and keep the temps around 300F with the heat gun? Tune by feel/ear? I'm kind of at a loss here guys because I feel like there is more power to be made but I don't want to toast my engine. Any help would be great. Thanks.
 
I really think there might be an air leak. Check that area first before going on.


I recommend going not to tune by temperature yet, but by sound and performance. You want a fine line of smoke coming out of the exhaust and full throttle. Then you can tune by temperature.
 
Make sure your temp gun is accurate first. I hear that the 3.3 does like to run hot, but the manual states to use 290 as the upper limit...which means you probably have a little bit of room with that. So if it feels like it's running OK...300 is probably fine. Every engine is a tad different....so what works for me...won't work for you. My revo runs an upper limit of @ 270 at the moment.
 
The LSN could be causing high temps too. Try richening that and leaning out the HSN a bit.
 
I agree. It's usually the LSN that's responsible for overheats that you can't bring down. Richen it by 1/8 of a turn, then let us know where the temp is.
 
Thanks guys, didn't think the LSN would affect temps that much but I will give it a try today and let you know how it works.
 
I agree. It's usually the LSN that's responsible for overheats that you can't bring down. Richen it by 1/8 of a turn, then let us know where the temp is.

Well reading this bit of information has saved me alot of headache. I reduced my LSN and temps dropped loads.
Thanks!

Ruhel™
 
Well, richening the lsn (which I assume to be the same as the HSN, counter-clockwise to richen) resulted in bogging and crappy throttle response so I kept it as rich as I possible while retaining good power. I drove the truck in circles and figure eights in the grass in my back yard, pretty much on and off the throttle constantly without shifting into second so speeds were not too high. I figured this is going to be the hardest load the truck will see. Temps were still well over 300F using the IR sensor above the glow plug but the truck had tons of power and response, pulling wheelies in the grass. :D

Another interesting note: when I pinch off the fuel the truck runs a very breif two seconds then stutters off. I do not get the increase in rpm/power of leaning out right before it dies out. Backing out the lsn does not really seem to affect this as much as it affects power and response.

If I never bought a temp sensor I would just be beating the piss out of this thing because it runs great and still blows a nice faint trail of smoke. :\
 
You'll still need to get your LSN set correctly. Don't make any adjustments till the engine is warmed up, then do it a little at a time with a couple of good runs in between. When you get sluggish pickup off the line, it's too rich.
 
You'll still need to get your LSN set correctly. Don't make any adjustments till the engine is warmed up, then do it a little at a time with a couple of good runs in between. When you get sluggish pickup off the line, it's too rich.

Thats the thing though, going by feel and sound I feel like it is tuned correctly aside from the temperatures. Any richer and I really start to loose power. Arg.
 
Well, considering the impact you had, I'd pull the engine and clean it really well then inspect for cracks in the crank case and/or carb body. The carb may have made contact with your spur in the accident. An air leak will drive up temps regardless how rich you run it due to always sucking too much air into places it's not supposed to be.

I have a feeling if you run it at a consistent 300F, it won't last long.

I busted my OS18TM in my jato, snapped one of the mounting flanges right off. I didn't know it right away, but all of the sudden, I couldn't get it to hold a tune. Ran hot, even though it was excessively rich via the needles. That's when I noticed a build up of goo under the engine, then took it out and the flange fell off. Which left a big gaping hole in the side of the crank case.
 
Back
Top