lordcontrary

Okay, I want to make sure my engine temp isn't too high... got a gauge but eh... under what conditions do I test it.

If I run it around at high speed I'll heat it up but it's also cooling off at the same time... isn't it? Do I stop it suddenly at my feet and check then?

OR

Do I prop it up on the bench with the wheels off the ground and gun the throttle? ( on the same note... will running it like this ( basicly with no load ) damage the engine?

Raddick

My Feedback: (1)

Drive it around like you normally do and after a good amount of driving just stop it near you and take the temp. Point the guage directly on top of the cooling head of the engine about 1" away from it. You may want to point it at a couple different places on the engine to get an accurate reading.

I'm not 100% sure but I believe "gunning it" with no load on the engine can be bad for it and it won't give you an accurate reading for normal use temperatures.

jkulhanek

1). You shouldn't be running at full throttle all the time, so just check it whenever you feel like! Remember, if you are checking temps between changing needle settings, give the engine 30 seconds to 1 minute to change temp and test again. Just check the temp peridically to make sure it's not too hot. Just drive the car up to yourself and take the temp, remember you should be trying to get the temp of the glowplug or the bottom of the head closest to the combustion chamber, both are similar in temperature. Make sure you are not taking the temperature of the exhaust header as it will be much hotter than the rest of the engine.

2). NONONONONONONONONONONONONONONONONONONONONONONONONO NONONONONONONO!!!!!!!!!!!!!!!!!!!
DO NOT RUN YOUR ENGINE AT WOT UNDER NO LOAD, you will possibly over-rev it, making it fly to pieces, or overheat it.

lordcontrary

Okay then...

So the basic point is, I am testing the cooling features of the engine ( heat sink... engine heat sink mounts ) for there effectiveness as well.

If my engine at full throttle could potentially ( I would never attempt -duh ) reach 300 degrees... but but the cooling features never let it reach >240 then all is well.

Since that is the case... I'm reaching max temps of 190. several top speed runs followed by a sudden stop at my feet and temp check ( on the cooling fins ). I will try getting the glow plug and combustion chamber as well now.

So I should attempt to lean it further? ( this isn't a huge issue, but adjusting my shift point is next stop, so I need to concider tweaking high speed more )

Also, should I expect the car to be able to reach high speeds when starting off cold? i do maybe 30 seconds of crusing, and high speed is not attainable. I usaully end up running thru a half tank before it really seems take off.

smokingcrater

a brief warmup (30 seconds) should be all you need. it sounds like you might be too rich, it leans out a little as your fuel level drops.

jkulhanek

If you are running a .12-.15 engine, 190F is just far too cold, DO NOT be afraid to run up to 300F, I have done for years with no problems.

Just aim the temp gun at the glow plug and take a reading.

You are getting too paranoid man, just check it every now and then. These little engines are very hard to seize as they run much colder than gasoline motors.

Polar_Bus

Then I am surprised you engines still run. 300F is too hot. All engine mfg's suggest an operating range between 240-280F. whenever I see temps creeping up around 290F I immediately shut them down, there is no reason to let them get up around 300F

Fuelman

My Feedback: (6)

Do not be afraid of high temps, heat makes horsepower. If high temps caused by a lean needle setting are your fear, then let your ears replace the the temp gun. Tune the engine where a high speed blast at full throttle on a half tank of fuel does not sag. If it sags, it is too lean and probably too hot. If it does not sag, you are probably OK.

I have never seen 300 deg fry an engine unless the heat was caused by over lean conditions. What I have seen is more car engines destroyed by folks with temp guns trying to achieve some magical number, such as 190. Too cold will ruin an engine, real fast.
Several airplane engines I have operate at least in the high 290's, many well over 300 and a few will only run exceptionally well when over 350 degrees. I have several car engines that put out the best power when they are over 325, namely my Fantom 15's and 18's. I have an OPS 12 that runs the absolute best in the 300 neighborhood. To demonstrate hot verses too lean relationship, I have on several occasions used a high oil fuel (18%, which makes them run hotter) in my Fantom 18 and got great power and fantastic throttability and great idle at 405 to 415 degrees sustained. No, they were not too lean.

One of my 350 degree airplane engines, the Fox 74 has never been rebuilt and I stopped counting 4 years ago at 100 gallons through the engine. My Fantom 15's and 18's and OPS 12 all are at least two years old and every one of them has a minimum of 10 gallons each through them.

lordcontrary

okay what is magical about the half a tank mark... and yes I have noticed that if your engine isn't tuned right... half a tank is usually where you'll notice... so...

What is it about that tank level?

The engine is fully heated?
the exaust pressure, at this level, does something?

Eh?
Heh?

Fuelman

My Feedback: (6)

The fuel tank level has influence on how rich or lean the engine runs since the engine has to suck fuel from the tank (which is usually lower than the carb spray bar), the lower the fuel level is, the harder it is for the engine to suck the fuel from it causing it to lean out slightly. Having tank pressure from the muffler or pipe helps minimize this, but does not eliminate this cause and effect relationship. The only way to eliminate the problem is to use a pump, which is costly and really not necessary.

To minimize the over rich and over lean effects caused by a full tank (rich) or by a nearly empty tank (lean): Do your needle setting at aprox a half tank of fuel, that way it will not be too lean when it approaches the end of the tank and will be less likely to stall due to overheating by being too lean. If you tune it (high speed and low speed needles) at a half tank for good crisp acceleration and no sagging at wide open throttle, you generally will not be too rich when the tank is full, or too lean when the tank is about dry.

jkulhanek

Uhhh 300F is not too hot!

I find certain engines will run at 320-350 with no problems!

qazx98948

im starting to think the force .26 is one of them. it will simply not run right below 260-270 degrees. i get the best performance out of it 270-280. and after 2 gallons, the compression is extremely tight, its almost impossible to turn over the flywheel with one finger. the common belief is that you will roast an engine if it goes a degree over 270, but i just cannot agree with that. a buddy of mine had a hyper 4 port that ran 280ish every day, all day, and it lasted him 9 gallons!

nitro stephen

The RB WS72, Can anyone give me needle settings and temps?

Mech747

dude 350 is like way too lean unless you live in the desserts or some thing and run it during noon my picco .26 would achieve maxx power out put around 210 i could put my hand on the heat sink for like 2-3seconds . but on the other hand these engines parts will stand under 350 conditions if it has proper lube anyways how could an engine go up to 340-350 range with proper lube[X(]

Fuelman

My Feedback: (6)

350 is not too hot when the tune is correct.
Look at an airplane engine, the head has much less cooling fin surface area, and generally they run a lot hotter, even in the prop blast. Most of your average ABC /ABN airplane engines last years of heavy use. Your average car engine has an oversized cooling heat sink head, in most cases it is way too much and makes them run way too cool, even when they are not run too rich. Your average car engine piston and sleeve lasts a season or less.
In an ABC engine (car, plane, does not matter) the piston is in a tapered sleeve. The top of the sleeve is actually smaller than the piston at room tempreture (thats where the pinch comes from). At operating tempreture (around 230 degrees F or greater ) the brass sleeve begins to expand to design fit and becomes about the same diameter as the piston. Any time an ABC type engine is run too cool for extended periods of time, the top of the aluminum piston is actually wearing away and becoming tapered so it fits in the cold sleeve. The engine may run great for a couple minutes until it gets warm then sags off and dies. When you have too much cooling fin surface area and the engine can not sustain design temps when correctly tuned, accelerated wear of the engine is the result.
An ABC engine will not be harmed by tempretures of 350 or 400 degrees F when the mixture is not lean. Some engines , where the stock cooling heads that are not oversized, like the Fantom 18, a correctly tuned engine is gong to run over 300 on a cool day and a lot warmer on a hot day, and it will run that way for gallon after gallon after gallon. On other engines, in order to get them to run better, I must block off a couple cooling fins by wraping tin foil around them, so they do not disipate the heat too fast.

Proper lube and tempreture do not have the relationship you think it does. Methanol in the fuel does the majority of the cooling, followed by the nitromethane. The oil provides little if any cooling factor and is there strictly to maintain a protective barier between moving parts. Methanol will suck the heat out of an engine just due to the latent heat of vaporization of methanol (which is very high), as the fuel vaporizes in the crankcase. Oil on the other hand does not vaporize and never becomes a gas, it atomizes into tiny droplets, some of which coat the internal parts of the engine but most of it flows with the vaporized methanol and nitromethane into the combustion chamber. In the combustion chamber, gasses (methanol and nitro) can be compressed, liquids (oil) can not be compressed. the more oil you put into a fuel, the greater the increased compression factor exists in the combustion chamber, causing operation tempretures to rise due to an increase in relative compression.
For instance, I was test running a Fantom 18 on a very warm and humid day (about 90 F and 70% RH), using standard 20% car fuel. The consistent temps were about 325 to 350 when correctly tuned for the day. To prove the point to a fellow racer who argued that 350 was way too hot and said that I need to run more oil (I tried to explain the relationship, but he did'nt get it), I got out some of my 20% airplane fuel which had 20% oil in it. After retuning to the new fuel and making a tank worth of fast laps, I pulled in and let him measure the temp. His jaw droped when he saw it was running between 405 and 415. I continued to run the engine on that fuel for several more tanks. That Fantom 18 still has awsome compression, even after well over 10 gallons through it (probably close to 20 by now), it has never been apart.

Again; higher temps when the engine is not lean will not hurt a darn thing. Elevated temps due to it being too lean will hurt the engine. Running an engine too cool will destroy the piston and sleeve fit faster than anything.

mase_00_7

Interesting thread[8D]

lordcontrary

Hey I'm back ( the original poster )... I agree -interesting thread!

I just got finished rebuilding from a wreck ( 75 bucks )... strangely I only damaged engine parts... fuel tank, engine carb & pipe... anywho. I'll be on the road again sat morning...

Reading this thread makes me wonder why I now own a temp gauge at all?

Since this thread keeps on trucking I'll ask another question related to heat...

What about vapor lock? I run it hot... it stalls... now it's down and out for 5 minutes. Cure? Too hot?

??? how about it?

inkfreak74x9

300 degreese, HA! I accedently leaned out too much and hit 475. It caused the blue anodising to acctually clear. It is now a light blue/brown. Why take your temp? when the car seems to be kicking ass record that temp then readjust. If you loose performance go back, if you gain remember that tempand so on.

Fuelman

My Feedback: (6)

[quote300 degreese, HA! I accedently leaned out too much and hit 475][/quote]

You broke the first rule of heat management! An engine running hot that is correctly tuned will not cause harm, an engine running hot because of a lean condition, not good, period.

When you run them lean, not only are you enriching the amount of oxygen per given volume of fuel, you are also starving the engine of oil. The additional oxygen to fuel ratio will spike up the temps just like the santa anna winds blowing on a small brushfire.


??? Yes, why take the temp??? There is no need to temp an engine, tune it with your ears and forget what temp it is running. What is the facination with the temp?

Example: Same engine different days, different cars, different plug, different fuel. If I have a .21XX engine in a car running gear XX, plug YY and Fuel ZZ and its 85 degrees out, I'm getting awsome performance, correctly tuned at 328 degrees. OK, different day, tossed the engine in a different car with a slightly different gear ratio, swaped to a new super duper cure the world plug and my buddies different fuel brand but the same nitro percentage, Since I got such wonderfull times at 328 degrees wtih the same engine the other day, I try tuning to 328 today, oops its a little cooler today, about 70 at the track. I can get it to 328 by cranking in the needle a touch, but wow is this thing fading out at full throttle and getting real lean near the end of the tank. What happened???????

What happened was you tuned to some magical number that had relavance only to that engine, that day, fuel, etc....., instead of using your ears and tuning it to the conditions at hand.

Fuelman

My Feedback: (6)

Let it cool down a bit, tune it so it does not quit and ensure the throttle stops and transmitter adjustments are so it does not stall. You could be running a bit lean, ensure you tune it with a half tank of fuel and it does not sag or fade on the long full throttle runs, then back it off (richen it) just a hair, not enough to lose any performance, just enough for a bit of insurance.

It is not vapor lock. What is happening is that the piston and the sleeve are at about the same size at operating tempreture. When it is turned off, the piston and sleeve are still at about the same size which will not create a great enough vacuum to draw fuel and then compress it for ignition at pull start or starter box speeds. If you let it cool a bit so the sleeve shrinks down to the size of the piston, compression and vacuum are regained.

Try not to shock cool it by squirting alcohol on the head fins, I have seen more than one invisible fire caused by that. What happens is that alcohol is squirted on a hot cylinder and then somebody tries to engage the glow plug drive and a very minor spark occurs and pooooofffff, lots of invisible flame and melting plastic. Way too dangerous, do not do that.

inkfreak74x9

My trx engine runs best at 318. Does not matter weather it is 72 or 92. My hpi gets its best at 277. I use the same plugs all the time so there goes that variable. I have my favorite fuel. One thats not to dry, but doesent fill my pipe with oil. Do I take my temperature Every time I run? No. It just seems to be that when I am running good these temps show up.

46u

My Feedback: (3)

I agree 110%

xRuddyx

my assoc. .18x runs 320 on high speed runs with 5 gallons through it. Tuning is a feel rather than a temp gun.

Fuelman

My Feedback: (6)

xRuddyx,
Glad to see you joined the topic, yes this is a ten year old thread but welcome.
I am glad to see that some of my basic teachings has followed through, tune to the conditions at hand by ear and forget the temp gun is something I know all about!

xRuddyx

Lol is it that old? How time flies? But nitro engines are still the same it's us that change as we get older huh? Just got back into it Mr. Fuel man. Nice to chat w ya