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Tuning question......

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chrisexv6

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If an engine is running hot on "factory" settings (factory in quotes because no one can ever really be sure the LSN is flush with the carb slide...........the threads are so fine that I dont think it could ever be exact except from the factory), and it is very rich on the HSN, is it possible that richening the LSN and leaning the HSN would be the way to fix it?

I ask because once I FINALLY (it took a while) got my replacement engine running, it runs great never stalls, etc, but its running hot no matter how much I richen the HSN. Pinch test is a little short (2 seconds), so I was hoping that I could richen the LSN and possibly lean the HSN to combat the high temps.

That sound about right?

-Chris
 
when u say running hot....how hot? what temp? which engine is this? .15 or 2.5?
 
Should have remember to include that info, too early for me :)

TRX 2.5, after some running around on flat ground with the body off I was hitting 308. Granted, I wasn't being very nice to it :) but I figured it should be a lot lower. It was also very humid when I was running it which I have heard will make it run hot no matter what.

But it never stalled, had blue smoke the whole time, still has a ton of compression, and started easily after doing the pinch test with the engine hot.

-Chris
 
the 2.5 is always gonna run a lil hot, even traxxas admits that. humidity shouldnt have an effect, i live in Florida, the humidest place in the US, and i dont have problems with my mills.

308 is a bit much though, i wouldnt feel comfortable with anything above about 280. How hard are u running the maxx? is this all full throttle flat street running?

Try this: Leave your needle settings where they are now, and do a lil dirt running, half throttle, with blips up to full speed for only a second or two.....do this for about 2-3 minutes, then check the temp ans ee what its at, and lemmi know,.
 
Thanks for the advice.

Yes, I was running it pretty hard (basically re-creating tank 5 of break-in.........3 seconds to WOT, hold there for 2. With a little playing mixed in ;) ).

And yes, the temp was taken with a low level of fuel (not totally empty, but not even up to the plastic seam in the tank itself).

I just want to get the temps down as low as I can, then Ill probably get a better cooling head. No, I wont lean the engine out even more with the cooler temps because I know whats really going on, I just want to cool it down so I can make the engine last.

I checked for an airleak by popping off the filter and placing my finger on the carb. Engine stops almost instantly (I think its *almost* instantly because I didnt get my thumb to cover the WHOLE carb inlet at once.........call me a klutz I guess). Maybe Ill tear it down and seal everything with Ultra Copper. but if I really did have an airleak, would it be running as well as it does? I didnt think so, but I guess stranger things have happened.

I'm also going to try a different fuel (my brother in law bought a Maxx the week after I did, and his runs great on Monster HP.........I was "smart" and went with Wildcat Eliminator because of the extra oil content), and I'm going to replace my fuel tank just in case (I've pressure tested it under water and didnt see any bubbles, but maybe its a "hot leak"?)

At this point I'm actually happy: I had this thing up for sale over the weekend I was so frustrated with it. But then I couldnt get it started!!! So I can't sell something that I know doesn't work. Now that its working, I kinda just wanna deal with it.........or just buy a new engine!!!

-Chris
 
I would back off the LSN just a tad and check it out. 2 seconds on the pinch test is a bit on the short side.

-Ed
 
I was also wondering: is idle temp a decent indication of the LSN setting? If its too lean, I figured that if you bring it in from playing and let it idle, the temp would stay the same or even go up. If its just right I would expect the temp to go down gradually, and if its too rich it would drop like a rock.

Is that theory a good one? If so, my temp was actually RISING at idle the last I checked it, so another thing pointing at too lean of an LSN.

I had hoped that Traxxas would set everything back to factory before sending my engine back, but it doesn't look like they did. The invoice said "HSN in: 4 turns, HSN out: 4 turns" (kinda like a mileage in and mileage out when you bring your car for service), but they left the LSN section blank.

-Chris
 
I recently had this problem with my TRX 2.5. It turns out that the engine was set incorrectly at the factory. The HSN was set to 2 turns out instead of 4. I hope my new engine didn't suffer any damage because of this. I have also learned from my LHS that a few others with this engine have had the same problem. So, CHECK THE FACTORY SETTINGS PRIOR TO STARTING ANY NEW ENGINE.
 
Originally posted by Nitroaddict
the 2.5 is always gonna run a lil hot, even traxxas admits that. humidity shouldnt have an effect, i live in Florida, the humidest place in the US, and i dont have problems with my mills.

...
Click to expand...

True enough about TRAXXAS mills always running hot. The TRX Pro .15 did, and now the legacy has been passed on to the 2.5.

I will call you on the humidity not affecting engine performance. If your humidity is relatively the same, then you will more than likely not notice any significant change in performance or any need to tune for the changes in humidity.

BUT...if you live in an area where humidity changes dramatically from day-to-day or week-to-week, you may find that the engine needs a little tweaking with the change to humidity.

Any time you change a characteristic of the air that the engine is breathing, you change the way the engine operates and will need to adjust accordingly (and humidity definitely changes the air).
 

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