Tuning/temp issue.......

[chrisexv6]

OK, put my maxx back to factory settings as best I could (HSN 4 turns out, LSN at a point where pinching the line gives me 2 seconds before it cuts off).

Took it for a couple high speed runs, then measure the temp.......300!!!??? I leaned the HSN out a little, and then the temp dropped down to a max of 270 after a couple more runs.

My issue is that with the engine so rich, I can feel the lack of top-end power. There is blue smoke coming out the whole time during the run, so I know its already too rich. You can even smell the nitro. It also shifts very late into second (later than during break-in).

Its about the same outside temp as break-in was, but its definitely more humid. After I richened it up, I was at 4.25 turns out on the HSN, which doesn't sound like much more than stock, but will that be the minimum I can leave it at? If so, my high speed is definitely suffering.

The truck is only a week old..........could I have toasted the motor already? Thatd be a major bummer (its only on its 8th tank). If it stalls, its never hard to restart, and it didnt cut out under high speed acceleration like overheated engines seem to do. Thats pretty much why I didnt know the temps were this high (I dont know how long its been this high, I just got my temp guage).

Any ideas? Any easy way to tell if I roasted the engine already? (aside from tearing it down). Is it possible I'm taking the temp incorrectly? (I have the Radio Shack infrared temp guage, and to get a reading I was putting it directly above the glow plug and resting the case against the black plastic ring around the top of the cylinder head..........perhaps I was getting a false high reading?)

Thanks!!!
-Chris

 

[LarryA]

Sounds like the LSN may be a bit too lean and the HSN too rich. Most engines I've set up end up around @ 1/2 to 3 turns on the HSN and about 2 to 2 1/2 on the LSN. Your position for the temp should be fine but I don't think you actually need to go against the head ring. I would think that 300 degrees is not unreasonable if it was immediately after hard running of the engine at full throttle. Anyway, I'd still gyess your bottom end is lean and the top end rich.

 

[chrisexv6]

Hmmm, k. So maybe Ill try richening the LSN until I get a 4 second pinch test (I've heard rumors that 3-5 seconds is better to shoot for than 1-3).

I didnt think the low-end was lean because I'm not really pulling wheelies (I had the low end set lean at one time just to get used to the adjustments..........I couldnt get the front end to stay on the ground.......granted, I only left it that way for a little bit, and it wasn't much leaner than stock), but I could be wrong.

And Ill try taking the temp from just above the head ring, and maybe a couple seconds after the WOT pass (I was literally braking it so it stopped about 6" from my feet right after a couple WOT passes and my hand ready to take the temp..........NO time for it to false cool-down........maybe I'm taking it too quick).

Thanks for the info!!!
-Chris

 

[LarryA]

Try taking a temp reading just after stopping when running at a normal pace. Figure, you hardly ever run WOT for any length of time, so why do it just to take a temp reading when it is not how a car is generally driven. The LSN should be set after the HSN. Set the HSN for best top end performanc then go to the LSN and set it for a good clean takeoff with maybe a minor hesitation. This should be very close to the ideal setting.
The way I now do it is not the way of general choice but I started a long time ago tuning more for performance than temperature, but never run without what I feel is adiquate lubrication. As long as I have decent smoke at full throttle and/or excess fuel at the pipe, then I'm satisfied with the tunning. I have never had much luck tunning by temperature. It seems every time I check it, it is for the most part, higher than 250 degrees (depending on how hard it was run). With checking after a WOT run, I almost always get readings over 300, but at low and varying speeds the temp has read in the 250-275 range. I have a Craftsman gauge and it is not the best but I was curious as to what he temps were. The problem is that the error factor for the gauge is quite high when you are looking at a 25-30 degree range. Ihope this made some sense and I'm not encouraging tunning for performance, just stating what I do. If I burn up a engine (which I have not done in over 5 to 6 years and in 5 different Nitro R/C's), I'll just buy a new one or install one of my spares.

 

[chrisexv6]

Yeah, I'm starting to realize that I might be putting too much faith in the temperature reading. Regardless of how *off* it might be, I can SENSE the loss in performance I had. Now, I ran the break-in with stock settings, but I didnt check them (someone mentioned their HSN was only at 3.5 turns when they took it out of the box). Assuming the stock settings were correct, I am WAY too rich on the high end at this point, so I will go back to 4 turns out and start again from there. Even at 4 turns out, the only complaint I had was the low-end, so just to be on the safe side I may stick with 4 on the HSN and then just concentrate on the LSN, and leave it at that.

And like you said, how often will I go all out WOT? I havent started bashing it yet..........I think I'm getting too used to running it up and down my flat street at WOT. Thats not really what its all about........I have a whole yard with obstacles waiting for my Tmaxx

-Chris

 

[LarryA]

I'm one to like more of the slower driving. Shure, I like flying once in awhile but for the most part I don't do stuff that tends to break things. I don't generally abuse my stuff to much of an extent. I still have my Super Athlete buggy after about 6 years and it still has the original engine I put on it and it runs great (no parked because I borrowed the radio gear from it for the Savage I have). That along with a Losi GTX which is just as old and still very good.
Pictures of my stuff minusthe Athlete in my gallery.