There are alot of comments about temperatures of engines but unless I have missed it, I don't see any acturl tempratures being given. What are normal and desired temps for two cycle engines? What is too Hot with WOT and what is too Cold with WOT? What should idle temp range be?

Gary

I've been wondering the same thing. This weekend, Im going to take some temp readings before and after my flights just to help me with my tuning. Im going to compare temp / RPM / sound, to try and get a better "feel" for getting a more contestant set up. Only because Im still a green noobie :-)

Scoot

IMHO don't get too wrapped up in temp readings......unlike a car/truggy/buggy/truck, we as aviators aren't at wide open throttle for very long, our engine heads are more open to airflow..and we move faster giving us more airflow than our distant cousins on the ground.....that's one of the reasons our glow plugs last several times longer......

I have never owned a temp gun.....didn't have a tach until I started doing gas...then it was given to me.....now if you have some issues with an engine a tach or a temp gun can be a good troubleshooting tool......get a base number so you have some deata to refer to

Good flyin

No one seems to have temperature data but it probably is important. Likely it will be easier to generate your own data. Please share your findings.

Bill

Actually KNOWING the engine head temp at WOT ( after a 45 second WOT run ) is a good idea.

I had all sorts of problems on a pusher prop plane that at first I could not figure out the cause of.



A friend walked up and used a laser temp proble to read the temperature at the base of the glow plug.

It pegged 480 degrees which given postings by "DOWNUNDER" ( a very knowledgeable forum member here on all things glow engine related... ) I knew this was far too hot.

I then richened the engine out until I was getting WOT temperature readings of around 280-300 degrees.

Though this sounded too rich to me on the ground, it was perfect in the air. All the problems disappeared!


I've often seen people sieze their engines because of too much heat, so now I walk up and perform the same test and fix which typically fixes their problems.

Hi!
Why do you want to know???
It's just one of those unnecessary things to know! Just like knowing how many amps a glow plug draws...

I been a pylon racer for 30 years and I can assure you in the racing world we don't take any temperature readings at all! We just set our engines by ear! Simple as that!
Our airplane glow engines just run at full power for how long as you want to , and you don't have to take any temp reading to know if they are running too lean or not...they are made that way! The temperature spektrum is very broad and as such our engines run just fine at very different setting.

These aren't liquid cooled engines. On glow powered boats that I run, temp is somewhat important. If there's too much water getting through, the motor won't produce the power. Obviously if there isn't enough, it will overheat. The ID of the nipple can be changed, or partially restricted.

On an airplane, air cooled, with constant prop wash cooling it....temp doesn't matter. It won't sound right if it's too rich, and it won't stay running very long if it's too lean. The same goes for the glow cars and buggies I run. There should be a noticeable smoke trail running at WOT. Transitions should be smooth, with a good belch of smoke.

When you shut down...if you spit or gleak on the head, it shouldn't sizzle. If it sizzles..it's too hot. The exhaust smell is another clue....I can tell when my truck is running too lean by the smell of the exhaust.

This is all that is important in regards to glow engine temps.

EDIT: A pusher setup is completely different. It then becomes like a car engine...and would require to be run sloppy rich, or have a large heat sink

Head temp even on tractor prop planes, is affected by prop size, and other factors.

Knowing the head temp helps to make sure you are not prematurely degrading the engine.

The "spit test" is not quite enough, nor are the engines designed to run hot.

I've seen all too many people tune up glow engines for best performance, back off a bit as they are supposed, only to have them seize in flight resulting in a deadstick or a crash.

While using the wrong prop was ultimately the culprit, monitoring the head temp would have pointed to the problem.

OK...all things considered, if you followed the suggested prop size and ran the motor sufficiently rich...you wouldn't need to worry about head temps.

Again, these are air cooled engines. Unlike liquid, closed circuit cooled engines....air cooled engine temperatures vary dramatically on the ground, in flight, 1/2 way through the flight, etc.

I highly doubt you'd be able to run your motor for 45 seconds, take the temp, then fly it at the same throttle setting and maintain that temp throughout the duration of the flight.

Is all you need is thermocouple and something to record.

I just have to question this. I fly on average three days a week, I was involved in pylon racing also for a long time and to this day I have never seen anyone, myself included ever seize a model aircraft engine. I have seen cranks break but never seen a model plane engine seize. I have yet to see any aircraft pilot use a temp gauge. Just how many engines do you see seizing up in any given year??

I am almost sorry I asked this question. There are definately alot of very strong opinions on the subject.

Being fairly new to tuning RC two cycle engines, i am looking for any tool that will help me tune. Having raced two cycle go carts [many years ago] temp was a key element in tuning. From what i read above, if i keep the WOT temp around 280 degrees F and 300F [on the bench] I should be safe.

Thanks Gary

There isn't a bad question...that is what the forum is all about......but at times people ask questions like the amp draw of a glow plug...that really has very little to do with operating an airplane....not saying your question had no merit......

You were basing your question off of past experience......most of us, including me, has never taken a temp reading...can a temp reading be useful? I suppose so if you have a problem and know the correct temp as a base data.....

In all my years of flying...I've only seen one engine fail due to over temp...on a helicopter.....where the cooling airflow is limited....There was no smoke and he was using 30% nitro......

Like I said IMHO I wouldn't get too wraped up in temps....more power to those that do...I just find that info is not that useful to me

A good tune by ear on the ground...and a good smoke trail while airborne has worked for me

GOOD FLYIN

To answer your question last year I saw five seize, including ironically one on a small pylon racer.

I had one of mine sieze the year before too.

jetmech05

Your comment regarding a good smoke trail is very timely. I am rebuilding an SSE that I crashed several months ago and am replacing the OS 46 with an EVO 46. Was having problems tuning the EVO, first had air leak which turned out to be caused by the carb not seaqting aginst the o-ring properly. Once air leak was fixed started tuning when I got it where I thought it was close, I went to WOT for 30-40 seconds and checked temp at the base of the glow plug, it read 310 degreed F. I opened the needle valve until temp was at 289 and guess what, a nice trail of smoke appeared. Looks like our two techniques both produce the same results, it's nice when divergent opinions come up with the same end.

Gary

I can tell if an engine is in a healthy temperature range by feel, but I don't know any numbers.

Yeah Downunder went into head temps on another long thread. Under 310 degress seems to be a magic number as I also learned.

The advice he gave has helped me help others with problematic engines.

A temp monitor has become a staple in my field box.

Much like using a tachometer, you can approach a correct setting, speed, etc. using the old mark 5 eyeball, but instruments help you greatly, to get more accurate readings and results.

In some cases, a tach and temp probe is the only way to assure a good engine tune... while at other times a recommended prop and a bit of fiddling suffices.

We've used a temp gauge once or twice just to see what we had. We've never used one for tuning an engine. We tune by sound and performance. A tach can help you find peak RPM, though you don't need one.

One time, we were running an O.S. Max .40 FP engine with an APC 10 x 6 propeller. The engine was tuned to peak RPM by sound and backed off a bit to insure it was running rich of that peak. We then put a contact temp probe against the cylinder head at the rear of the engine, where airflow was at the lowest velocity. We measured 375 degrees F. The engine was running on 10% Omega fuel. It would run "all day" at that needle setting.

As far as temps go, if you rely on them to find the "correct" needle setting, you are setting yourself up to destroy your engine. They are not quite reliable because everyone's engine will have a slightly-different installation and setup. Different fuels and propellers will also make quite a difference. One person't "good" temp will destroy another person's engine....unless the temp suggested is "stupidly low".

When it's running normally, a model airplane engine will become hot enough to cause a severe burn if you touch the cylinder head...that's a normal thing. You just don't touch the engine until it's had a chance to cool off after it's been run for a while.

Because they've become available, too many people think that using a temp sensor of some kind will make setting the engine easy...like using a formula: "Do this, then that and you'll be OK". Not going to happen.

Basically, at full throttle, if you give the fuel line a quick pinch and the RPM goes up, you can lean a bit. Repeat the process. If the RPM stays the same or goes down, you richen the needle until you get a small RPM increase with the pinch. You're ready to fly. Listen to the engine in the air to see if it leans more once airborne...usually it does, and you may have to richen the needle a bit more. Eventually, you'll get the hang of getting the engine set correctly.

Don't get too hung up on smoke, or lack of smoke. Some fuels and engines smoke a lot and others do not. Using the pinch test, or a tachometer, to be sure you are running a slightly rich needle setting is (in my opinion) a better tuning indicator than smoke volume.

Carr, great point. Today I was flying planes running YS engines, one the old 120NC and one the 1.10FZ. The 1.20 is pretty old and may be in need of some R&R but I always wait until they are on there last legs before I go into them. The smoke trail on the 1.20 is so thick it looks like something out of a WWII movie just before the plane hits the water. The 1.10 has a very light oil trail, sometimes hard to see. No seizures yet but I'm keeping an eye on that 1.10. My OS .91 FS engines have very little smoke trail too, they are a bit on the newer side compared to my older YS engines though. Just a good tach and the pinch test if I can get to the fuel line is all I have ever done.

How long do you hold it before you say its perfect ?

It looks like people are looking for that magic number again. Just Google magic number and you will get nearly half a billion results. The problem is that every engine is as different as each operator. I can't condense 50 years of operating glow engines into a few sentences, and am willing to bet nobody else can either. But I do have a few general observations. Most problems are with the set-up of the fuel system. Most operators tend to run their engines too lean. Most fail to monitor the health of the engine over time. Here are a few things that you should be aware of if you are running two cycle glow engines.

Fuel system
Fuel must be very clean, as very small particles of anything will plug up the needles changing the mixture.
Lines to the tank must be as short as possible, make sure there are no leaks.
Tank height should have the center line of the tank no lower than 1/2" below the center of the carb where the spray bar goes through.
The clunk inside the tank should be able to touch both the top and bottom of the tank without touching the back. Fuel line grows in length over time once exposed to fuel, so start with the clunk about 3/8" from contact with the back. Use a two line system if possible.

Running too lean
Pretty much self explaining, but if everybody is doing it then nobody seems to recognizing the problem. When on the ground, an engine is under a much different load than when in the air. Most sport models with fairly clean (low drag) airframes will have the engine unload 1500 to 3000 rpm over the ground rpm. This also requires more fuel. Running light loaded props helps, especially with engine with low time on it. But for a broader needle range which is much easier to tune, run a lower pitch prop for a given diameter. While you might thing that you will be flying slower as a result, often the air speed is nearly the same due to increased rpm.

Condition of the engine
I have often sat on the sideline and just listened to engines in the air. Usually in a few seconds you can tell the condition of the engine, from being too lean, to even the condition of the bearings. A bad bearing has a very distinct sound that most seem unaware of. Complete bearing failure will do enough damage to a engine, that is not economic to repair, so before running an engine turn it over and feel the bearings for smoothness. If you start killing glow plugs for no reason, it's usually a bearing going south. The other general problem is a loose head or back plate, bad o-ring on the main needle or air leak at the carburetor base.

It been in my past experience that any more than about 1/2 second contact with the engines on the planes that I just landed ended up with shiney,no fingerprint blistered fingertips with the stares of other specaters wondering why the guy over there is flailing his hand like a wild man all the while jumpimg up and down going round and round !?!

I agree on the pinch test,not so much on the tach,different props and pitches can vary RPM,s a lot.

I had the same question. I have background similar to Gray Beard's, and I have never seen an engine seize. I once test flew a Q40 pylon plane that went extremely lean after takeoff - I could not shut it off and had to fly it around until the tank ran dry. All of my friends stood next to me and joked about ruining an expensive Nelson engine on the first flight. When it landed, it smelled like hot brakes. The glow plug and head were both blue, but the engine never seized.

Kurt

Your fuel is too mild to do much damage. We burned pistons when we had a lean run on 65% nitro. I had a shaft run once after scraping off the wing and landing gear. The engine ran for about 4 seconds until it seized. It had beat out the bushing material in the rod's lower end, and ran it through the engine. Must have been running at about 40,000 or so. When it stopped, the rotating energy had no place to go and the engine pulled it's mounting lugs loose from the case.

As to touching the hot head, Yeah you can do that if you have the right technique. You first wet your finger and that liquid will turn to steam with a quick touch. But a better way to get an idea of how hot you are running is to feel the exhaust gases. Start some distance away and collect a bit of oil on your fingers. When you find a comfortable distance, then experiment with the mixture and see how the exhaust gas heats up with changing the mixture.

Note: this assumes that you can walk and chew gum. A screaming engine is nothing to play with unless you have a plan in mind.