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Gas engine temp.

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Old 09-19-2012, 06:23 AM
  #1
SJN
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Default Gas engine temp.

Hi guys.

I just bought one of those laser guided infra red temp guns.
I want to use it on my cowled ZDZ 90 engine to see if the cooling is sufficient in my scale warbird.

What sort of temp should I be seeing while the engine is running, and just after shutdown when I messure on the front fins ?
And how hot can it be before the engine is damaged when messuring on the front cooling fins?

I realize that messuring on the cooling fins in front are ofcourse not the hottest place on the engine, but there must be a a rule of thumb to how hot you can go



Heres a picture of my cowl.
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Old 09-19-2012, 07:48 AM
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Default RE: Gas engine temp.

The front of the engine is the worst place to aim your IR gun at.
Try to get access to the spark plug base. Paint it black! Aluminum reflects the weirdest readings unless the surface is black. Take good care in reading the included angle when measuring. The smaller, the more accurate.
When measuring the spark plug base using a small angle IR device pointing at a black surface, you should see readings of about 180°C to 200°C in a well tuned engine at full throttle static. The back of the cylinder topmost part should be about 150°C, but is almost impossible to read using the IR gun.

All in all, an IR temp gun is quite difficult to get good readings with, and for that reason is near to useless unless you know, and adapt to it's limitations.

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Old 09-19-2012, 07:56 AM
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Default RE: Gas engine temp.

off the front of the engine you will likely see 150 degrees C at the most. The base of the spark plug is the best location to measure temperatures short of drilling holes into the engine for thermocouples. Like Pe stated paint some flat black paint on the location and use your IR tool at the same angle, etc when you make the readings. 180 to 200 or so degrees C seems about normal for the engines with lots of cooling fins. Some of my engines that are, more or less, converted glow engines with short fins tend to run more hot though upwards of 225 degrees C or a little more even. The engines tend to run more hot on the ground in a static load situation versus when flying in the air too, where the prop unloads off the engine more.

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Old 09-19-2012, 08:15 AM
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Default RE: Gas engine temp.

Thanks guys.

you ask of the impossible
there is no cutout in the bottom of the cowl as the cylinder does not sitck out......so I cant messure the base of the ignighter.


ahh well, we will see how it goes once I complete the plane.
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Old 09-19-2012, 09:39 AM
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Default RE: Gas engine temp.

Don't despair; there will be a next time for sure.
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Old 09-19-2012, 01:36 PM
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Default RE: Gas engine temp.

Earl, 225 C is 437 F. Did you mean 225 F?
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Old 09-19-2012, 06:04 PM
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Default RE: Gas engine temp.

Well I got this static engine reading early in the morning before the ambient temperatures went over 105 degrees F that day. I did have the IR temperature tool reading 426 degrees F or so when it was really hot outside. But you are correct 225 degrees C might be too high then, 426 degrees F is about 218 degrees C. The measurement is at the base of the spark plug on the head right there. I thought for sure I had a pic of the high temp reading on my PC here someplace, I am still looking for it.



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Old 09-19-2012, 07:25 PM
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Default RE: Gas engine temp.

Boy you guys run hot engines, my 3W85 has a instruction book recommended temp of around 100 c and i try to keep it under 120c.
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Old 09-20-2012, 03:58 AM
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Default RE: Gas engine temp.

Very nice plane sjn hope it goes well and thanks pe,earl etc for going some way to explain the method for measuring heat on your engine.I'm more in dubs camp or way of thinking as i used to worry about the engine temps quite a lot.Now i put a lot of thought into venting the cowl well and just directing the small inlet hole directly onto the cylinder with a cowled engine,run it rich and go from there.They soon let you know how it's all going
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Old 09-20-2012, 04:16 AM
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Default RE: Gas engine temp.

Well my higher than expected engine temperatures are probably not what everyone else will measure. I feel that the temperature range as mentioned by Pe Reivers is about what people should expect. But the engines with the short fins on them that look like glow engines will run much more hot though.

Doing this with a small 9cc engine is probably over the top. But it does run pretty good though. Plus flying it a lot here in the hot summer Texas weather doesn't help matters much either. But it is cooling off now with summer ending. You do not need to put a Walbro carb on this brand engine, it was an experiment I was conducting.

I think this type of engine needs more cooling fins on it. I have seen others using different brand engines like this glow engine conversion having higher running temperatures too.







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