head temp. on 2 cycle engines
 

What would be the normal temp. range be on a 2 cycle engine?

RE: head temp. on 2 cycle engines
 

not sure, most of us just use a tach and or our ears to tune em and base it off RPM and smoke volume and color.

The temp range setting is for cars. Cars do not have near the airflow and you can't tune them under load properly hence using a temp guage.

If you trying to guage temp to figure out a glow plug heat range you base that off the type of engine and the amount of nitro your running. The more nitro the hotter the plug.

RE: head temp. on 2 cycle engines
 

275 - 300 F at hottest place

RE: head temp. on 2 cycle engines
 

tree:

This article

http://www.flyrc.com/articles/tune_your_engine_2.shtml

states that ”The ideal model airplane engine (.29 - .75 in³) cylinder head temperature occurs in the range of 350-375° F”.

However, using a infrared sensor, I have measured only less than 300° F in my engines.

RE: head temp. on 2 cycle engines
 

All the above is true, but as Redfox pointed out we just don't worry about it on airplanes. There is ample airflow over the engine and we usually don't worry about it overheating. There are occasions where a poorly engineered cowl will cause an engine to overheat, but we still usually don't worry about the temperature it gets to. Just to open up the cowl for more airflow.</p>

Ken</p>

RE: head temp. on 2 cycle engines
 

Sorry, but when you have "hotter" fuels (more nitro), you use colder plugs. "Hot" fuel = "cold" plug and "cold"fuel = "hot" plug.

RE: head temp. on 2 cycle engines
 

yep, whoops

RE: head temp. on 2 cycle engines
 

Yes.


But rhetorically, for those playing the home version, be aware that in pusher prop configurations, you SHOULD be monitoring head temps.

I had many problems with my Bobcat 50, using a GMS .76 engine in a pusher configuration until someone suggested I check the head temp.

I found that it was soaring over 400 degrees when i ran up the throttle using standard tuning proceedures.


I was able to use a laser thermometer, to adjust the needles and bring the temps down to under 360 degrees or less.

Once I did this, my engine problems disappeared... though the engine ended up being set far richer than I ever would have normally done.

RE: head temp. on 2 cycle engines
 

opjose:  How did the engine run with having the mixture running so rich?  I've never had a pusher config and am interested in what you found as well as how the engine ran after setting it up to run so rich.  I can only imagine how a typical front engine config runs when set up rich.</p>

CGr.</p>

RE: head temp. on 2 cycle engines
 

Seeeing I mainly fly CL stunt I've got no hesitation running an engine rich even in RC. I had a Rossi 45 in a sport plane and I'd run it in a 4 stroke flying level because I'm not a speed freak :) but the moment I'd go out of level flight the engine would instantly go into a very powerful 2 stroke. However this probably wouldn't work in a pusher configuration because with the nose pointing up the tank would then be way above the needle valve so should run even richer.

If I was running a pusher I'd fit the same size normal prop to tune the engine first (a bit on the rich side) then fit the pusher prop and go fly.

RE: head temp. on 2 cycle engines
 

Unfortunately that was exactly how I tuned the engine.

I used a standard prop in a test stand and set it up as I normally would.

I ran several tank fulls through the engine without any problems or hesitation.

I was running the engine slightly rich for a tractor since it was still fairly new... but it seemed fine.



When I installed it on by Bobcat with a pusher prop, the engine siezed after running it for less than a minute.

At first I thought something was wrong with the engine and I took it home & pulled off the head to check it out.

Fortunately there was no damage.

Next time out I tried re-tuning it, and I got it to run somewhat ok, but I would always have some form of problem after a few minutes.

That is when I got the suggestion to check the head temp.


A friend came up with a laser thermometer and that is when I saw that the temperature was soaring.


Downunder I thing it was one of your sage posts, that I recalled at that time, from another discussion.

I remembered that the temperatures the engine head was attaining were too high compared to what was talked about in that discussion.


So I started richening both the high and low end mixtures until I got it down below 360 or so.

At this point the engine STOPPED cutting out after a few minutes.... however I had a real problem with it bogging down at idle and when moving the plane down the field for takeoff.

The engine was way too rich during and during one takeoff and the plane went in.

The components are awaiting a move to a replacement airframe at the moment, but I'm still worried about the overheating.