Hey all,
I'm running a fully coweled OS 1.6 FX in my 1/4 scale and while I think it's set on the rich side, it seem awfully hot when I land, although it's running fine. I'm going to bring my Pyrometer next time to check the temp, but I don't really know what it should be. does anyone know what a normal operating temp would be?
RickP

Basically, don't worry about cylinder head temperatures. It will be normal for the engine to get hot enough to give you a severe burn if you touch it. We've measured cylinder head temperatures on airplane glow engines as high as 375 degrees F! This was using a contact probe at the airflow stagnation point at the rear of the cylinder when the engine was running on our test stand.

If the engine is running on the rich side of peak RPM, and you are using a quality fuel with a high-enough oil content (O.S. states no less than 18%), then you won't have any problems.

bill baxter
Hobby Services Manager

If the head temperature is not critical, then why do all the helicopter guys go to such extremes to keep the head temperature between 190-240?

Of course cylinder head temperature matters. If it didn't, then we wouldn't have to be concerned with engines overheating.

I have in front of me an engine review of the OS FF-240 4 cyl. 4S done some time ago by Clarence Lee. Clarence measured the cylinder head temperature under the glow plug of the front and rear cylinders on one side of this flat four with a thermocouple and pyrometer. Both cylinders measured the same at 280 F. This is, of course, a four stroke engine that needs to run hotter than a two stroke engine that fires every revolution. The temperature range of 180 to 240F supplied by Oakley seems reasonable.

A glow engine can run too cold as well. If the head temp. is not high enough, then the glow plug will go out. The old K&B 45 Sportster was an example of this extreme. The cylinder had too many fins and was overcooled. This in turn cooled the head and after prolonged idle, the engine would quit. Toward the end, K&B machined the fins off the head to increase the head temperature and keep the glow plug lit.

Bruce

On an ABC engine, you want your head temp to be 350 degrees F or above. Much cooler and the sleeve and piston won't expand the way they are designed. That will cause excessive wear on the piston crown and cylinder sleeve. My understanding is ringed motors can afford to run much cooler since there's no "pinch" at TDC to worry about.

Hey,
Thanks for the feedback. This thing is running so good I'm afraid I'm gonna blow it up LOL. I ran it last night and opened the needle valve 1/2 turn and it was gargling a slight bit rich in the air. I'll crank it back in 1/4 at a time to find the sweet spot.
I reciently switched (due to my Hobby store, not by choice) to a "Wild-cat" fuel. I don't know the oil content offhand but I do know that after a while the exhaust appears a darker color that drips from the muffler. This is leading me to belive that it's too hot too.
The green "Cool Power" I prefer does not have this tendency with the exact same needle setting. I open it the 1/2 turn and it's too rich. If you have any more input I greatly appreciate it.
Thanks
Rick

Rick et al,

I have some thermocouples and a pyrometer and will try to get some readings on ABC and ringed engines this weekend. I plan on silver soldering a thermocouple to a glow plug or gasket so the temperature readings will be taken at the plug location only.

I will report back next week. Happy Fourth!

Bruce