Planecraz3d
50cc
It is in the second fin from the top of cylinder and the sensor is on the front. It went to 300°. Not hot enough to do damage but I didn't keep flying get to see how hot it was going to get either.
Extreme Flight Owners
- Thread starter JaseTheAce
- Start date
you may actually be hotter than that.
i have a Jeti radio and telemetry system, and i have done extensive testing with sensor placement. if you place the sensor in the "shadow" of the prop wash, you will see your temps will be even higher.
this is contrary to traditional thought on temps of engines. most people have used an IR gun, and then they check the temp by aiming the gun to a point on their engine, usually this is the front of the cylinder, and usually once airplane lands or before take off.
this is very inaccurate.
the testing i have done by changing placement of sensors reveals:
the temp in the back of the cylinder, top fin, is about 100 degrees higher than temp in the front of the cylinder, same fin.
the crankcase temp is about 100 to 150 degrees lower than temp in the top of cylinder rear area.
the hottest area on the engine is in the top of the cylinder, near to spark-plug, where the explosion occurs. the prop wash in the front of the cylinder significantly cools the the front of the cylinder, the second law of thermodynamics: The second law states that heat flows naturally from regions of higher temperature to regions of lower temperature, but that it will not flow naturally the other way.
so as the prop wash cools the front of the cylinder, then the rear of cylinder, which is hotter, heat then flows from the back to the front, the prop wash then blows the heat energy out the "vent" hole of your airplane. i do not know how they came up with 3 to 1, but the more exit the better, and if you make baffles, then you can direct prop wash directly over the cylinder fins, to force the cool air to passed thru the fins and remove the heat from the fins.
very interesting, i put (at same time) one sensor in the front of the cylinder and one behind the cylinder.
ran the airplane, during the whole time, temp in front was lower than in back, as expected.
when i turned off the motor, within 1 minute, temp in front went up high and reached same temp as back of cylinder, then over 5 minutes, both temps went down same rate.
here is a picture of where i place the sensor.
17875=12265-sensor position for da 70.jpg
Planecraz3d
50cc
Thanks Orthobird. I knew it was being cooled by prop wash, but didn't know it was to that extent. I will move the sensor today and see what Temps I get. The cowl is still off so it won't be hard to do. I will post results later today.
O
Ohio AV8TOR
I am a little confused as you say the probe needs to be in the shadow of the prop wash (which to me is the back side of the cylinder), the diagram you posted says the back of the cylinder but the picture on the right shows the probes on the front of the cylinder.
However I have not had a cup of coffee yet so maybe I am missing something in your conversation.
O
Ohio AV8TOR
Thanks, I wondered about that. Is it actually touching the cylinder wall or fins?
I have the DA35. I took IR gun readings that all looked normal the first week. Now I have a sensor for realtime temps. I placed the sensor in the second from the top fin space and it is on the back side of the cylinder. Temps the first time were 295° peak. It worried me a bit but the IR gun temps still read normal on the ground. Anyway in much cooler temps on Saturday (70°F) the temp peaked at 260°F. I'm planning to add a baffle that will put air thru the fins from on side to the other. We'll see if this lowers the rear head temp or not.
O
Ohio AV8TOR
Your not alone. The funny thing is I sometimes get compliments at the field too.