You're too cool (engine temperature)

[Dad-to-a-Marine]

Here is one for all you engine tuners out there. I bought my MT about a week ago and started to do all the maintenance that the pervious owner had not. Part of this was to try and tune the engine for best performance. As far as I can tell it was still on its break in tune, it has 15 tanks through it now, with the idle set a little high and the needle out 3.5 turns (it is a one needle carb with idle screw adjustment). I ran it kind of hard through a tank and the engine never went above 140* so I thought I would lean it out. I start on my bench with the exhaust gassed to outside the house and let it run for 5 minutes with med run blurps for about 15 seconds ever minute. When I took a temp reading and it was a steady 140* in a 70* room (I used a standard thermometer and not a digital one). I then started to lean it out.

I brought in to 3.0 turns and let her run for 5 minutes and the temp went up to 170* and the idle was pretty quick. I brought the idle back down to a slow/no tire spin and checked the temperature again, still 170*. I then turned in the mixture screw to 2.75 turns and idled her back down. Now the temperature was up to 180* and holding steady. I have a good idle and still good smoke but 180* seems a little low on the temp scale to me. During the tuning time I ran a half tank through it and the 180* was a steady 5 minute reading. So now what do I do? Do I leave it alone and accept the fact that she won’ run any hotter then 180* or try to bring in the mixture and aim for 200*? The outside temp here is around 40* during the day time and during the summer it can hit 95* plus. Right now I do run it a lot so is 180* in this kind of weather good for it or am I looking for trouble? (BTW the heat sink temp never went above the 180* mark so I know I am getting a good reading.).

[mad-quick]

no no my 24.7 runs at 140-170 and lhs say great i have checked on the motors inside and it looks very good if not broke leave it alone

[jhunz]

i understand that you're concern is on engine temp. but i would consider tuning it to performance, not temp. run it normally outside for warm-up. then run a WOT pass. lean needle slowly, just make sure it doesn't bog down when you do WOT pass. as long as you can see trail of blue smoke in your exhaust, i think you're OK.

[quicklimegirl]

i understand that you're concern is on engine temp. but i would consider tuning it to performance, not temp. run it normally outside for warm-up. then run a WOT pass. lean needle slowly, just make sure it doesn't bog down when you do WOT pass. as long as you can see trail of blue smoke in your exhaust, i think you're OK.
wise-.. new member.Max perfomance @ max smoke = perfect tune and no heat issues

[zakerid]

i would also say that running an engine with no load (out of vehicle) is not good. if anything when running outside of a vehicle use a prop or something.

[Dad-to-a-Marine]

i understand that you're concern is on engine temp. but i would consider tuning it to performance, not temp. run it normally outside for warm-up. then run a WOT pass. lean needle slowly, just make sure it doesn't bog down when you do WOT pass. as long as you can see trail of blue smoke in your exhaust, i think you're OK.

I took it outside today and ran it through our mush and snow alley way. After warming her up for about 5 minutes I took you suggestion and leaned her out by watching the performance and smoke output. I found it surprising as to how sensitive it was to small turns on the mixture screw. Leaning it by 1/8 turns I was able to get it to go into second gear, something it had alone done at hit and miss before, in about 20’ under no load and 50’ while going up a small hill. I tested the temp using the “spit” test and found that there was only a ¼ turn on the needle between sizzling the spit right off and no sizzle at all. I left it where it didn’t sizzle, had good smoke and could hit second gear in about 30’ under no load. After running I brought it in and found the needle to be right at 3 turns out for a soft seat.

From my racing days, I still have my IHRA SS class license, I could tell the tune by the plug. But, on these small engines I have noticed that the fuel doesn’t leave a deposit on the glow plug like a gas engine will on the spark plug. Seeing this I figured that there must be some kind of deposit burn on the cylinder head. When I pulled mine after today’s run I saw a light brown coloring where the flame travel occurs. What would be a good or correct color? Is it normal for there to be no deposit on the glow plug?

As you can tell I am kind of detailed orientated and love to tinker to get the best possible setup. One other thing that has occurred to me is, does this kind of engine need to be adjusted for the temperature of the day/week? If so what kind of temperature range are we talking about before you would retune it?

[Dad-to-a-Marine]

i would also say that running an engine with no load (out of vehicle) is not good. if anything when running outside of a vehicle use a prop or something.


I guess you missed the part where I talked about the tires spinning. I tunded it fully installed in the truck (I built a stand for the truck that has a tie down strap so I am assured that it wont get knocked off and run into a cat... or something that really matters.).

[zakerid]

guess i did... l'm a little slow

[jhunz]

Is it normal for there to be no deposit on the glow plug?

RC plugs normally don't leave deposits unlike car spark plugs. as to the piston head color, not very sure bout the appropriate color. mine is also brownish. i don't know if the fuel color has an effect on the deposit's color. i use odonell fuel which are clear...

If so what kind of temperature range are we talking about before you would retune it?
usually, engine manufacturers have their own temp range for their engine. but they i still suggest tuning it to performance as conditions for each users are different (i.e. altitude, ambient temp, track condition you're running etc.) i have a fantom engine that manual says it needs to run hot.. i think like 270-320...got it tuned to performance and i was in their recommended range....

[Madmann135]

Well... I had a Cool problem with one of my engines after I modded the exhaust port some.

At first I had the engine at a nice 220-240 with respectable power. After modding the exhaust port (after modding the intake ports) I noticed a more noticable preformance increase and drastically decreased head temps (about 150-170). I freaked because normal running temps of the engine are 220 and that was a drastic head temp decrease to me.

I leaned out the top end some but that lead to a lean mixture setting (glad I add extra oil to my fuel). Then I remembered that the low speed helps control the temps of an engine so I leaned it out some which helped bring up the head temps to normal temps (220-240), not to mention a more stable temp range (near constant 225), bring out a little more power and tame the Idle more.

NOTE: I use a low cost but effective IR temp measureing device and aim it at the glow plug.

Moral of the story. The high speed and the low speed needles control engine head temp.
Work with the high speed needle before you work with the low sped

[JoeMAXX]

I was running my TMaxx this weekend in Colorado at about 8500 feet above sea level. Brought it up to the Girl friends house to play. 30% Nitro 45 deg outside with a medium heat plug.

Truck was tuned last summer at 5200 feet and ran in the low 230 deg temps at 90+ degs outside temps. Could not get it run cool no matter how much I richened the the HSN. Darn thing after about 5 attempts still would still top 300 Deg. My thought is I need to drop back down to 20% nitro if want to continue to run at that Altitude or drop in a cold plug. I will have to see when winter is over and the air is a bit thicker and the outdoor temps are higher.