I have DLE 111s in my 33% OMP Extra 330Ls. I am wondering what is an acceptable operating temperature. Using Spectrum Telemetry, I am measuring the engine temps at the back of the cylinder to head junction. I am seeing 200-250 degrees F at ~ 1/2 throttle in 50 degree F ambient air. When I run full throttle, the temps jump up to 300-340 degrees F. The spark plug electrode is staying chocolate brown, so I think I have the carb tuned spot on. I was just wondering if these (300-340) temps are normal or should I install some baffels. ?

One cylinder runs a little hotter than the other one?

No. That is not what I said.
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While they usually won't immediately die if you go a bit above it, I like to consider 350 F a reasonable max cylinder head temp. 300 F provides more margin for error; lean runs, hot days, slow or no airspeed at max throttle, etc.

AV8TOR

I don't know if it is possible to really measure the engine temperatures well, as it can vary from engine to engine (even the same model and make). You usually have to use thermocouples buried inside the engine at various places to get the best readings. Exhaust gas temperature looks like a good way to measure the temperatures too.

But your temperature readings tend to be about what I get on some of my engines. So you are in the ballpark, so to speak.

Using a Infrared thermometer is tricky as the temperatures can vary a lot depending on the shininess, color and reflectivity of the surface. Using temperature probes can be a problem as the sensor is on the surface and may not be getting a really good contact to it either.

Some gas engines will read higher than others, it depends on the air flow through the fins and over the engine, as well as how many cooling fins or surface area the engine has to help dissipate the heat. Using a really good high grade oil can make a noticeable difference too, as the oil reduces friction which reduces the heat too.

I am trying to get some opinions that will help me decide if I need to baffle the cowling to get the top end temp down. The plane in question has been running fine all summer. But now I have the engine broke in and am getting the carb tuning just shy of lean. So, I wanted to see what other folks are experiencing for temps.

Hey Len have a look at post 23 by PE. on this thread http://www.rcuniverse.com/forum/m_11...m.htm#11071695

250 -300 F. is safe.

PE DEFINITELY knows what he is talking about, but personally if I had an engine hit 400 F I would be very unhappy....

AV8TOR

<p class="MsoNormal"><span style="font-size: smaller;"><span style="line-height: 115%; font-family: Arial, sans-serif;">Thanks for the information. <span class="apple-converted-space">It seems like getting the max temp for my sport setup below 300F, maybe worthy of trying a few mods. At the very least, it is obvious to me that I have to do something with the Extra I have on the bench that I am building for 3D.</span></span></span><span style="font-size: 5.5pt; line-height: 115%; font-family: Arial, sans-serif; background-position: initial initial; background-repeat: initial initial;"><span class="apple-converted-space"><o></o></span></span></p><p class="MsoNormal"><span style="font-size: smaller;"><span style="line-height: 115%; font-family: Arial, sans-serif;">I am using the standard mufflers that come with the DLE 111s. On the sport Extra, I have two large openings in the bottom of the fuselage&rsquo;s canister space (behind the mufflers and not used) that provide warm air exit paths. I think I will add an exterior air dam in front of and below these two openings to create a bit of vacuum. This could improve the warm air exit. I may also add a baffle inside the canister area to deflect the warm air down and out of the canister area versus counting on the air trapped in the rear portion of the canister area to divert the warm air out. Then, I'll take some new measurements. I believe in taking one step at a time and then retest, etc..<span class="apple-converted-space"></span> </span></span><span style="font-size: 5.5pt; line-height: 115%; font-family: Arial, sans-serif;"><o></o></span></p><p class="MsoNormal"><span style="font-size: smaller;"><span style="line-height: 115%; font-family: Arial, sans-serif;">I am a little hesitant to baffle the air from the front of the cowl opening to the engine. If I did that, I am not sure where the cooling air for the mufflers would come from.</span> Maybe, I&rsquo;ll try a baffle from the top of the cowl&rsquo;s air inlet to the top of the cylinder&rsquo;s cooling fins. This would at least preclude air from going over the top of the engine w/o cooling it. If I do this, after some testing, I may look at something to deflect the air coming off the back of the cylinders down toward my openings.</span><o></o></p><p class="MsoNormal"><span style="font-size: smaller;"><span style="line-height: 115%; font-family: Arial, sans-serif;">This may take a few weeks as the outdoor flying is winding down here and indoor flying is ramping up. I&rsquo;ll keep track of the mods and related test results to post when I get this complete. Thanks for taking time to respond to my question.</span></span></p><br type="_moz" />