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Question on outside air temp effect on glow engine peak RPM

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Question on outside air temp effect on glow engine peak RPM

Old 01-15-2021, 04:52 AM
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ahdofu
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Default Question on outside air temp effect on glow engine peak RPM

Do you see a change in the peak RPM of a glow engine in cold vs. warm days? In summer time this particular engine of mine was peaking at 9400 RPM (OAT ~ 75 degs). Yesterday it reached 8900 RPM at OAT of 50 degs. On one hand the higher density of air affects the power needs of the prop but then the higher air density should also help the motor as well. Anyway I was wondering what folks have experienced. BTW this is an OS Surpass 91P glow engine using a MA 14x6 prop with Omega 18/15 fuel.
Old 01-15-2021, 10:58 AM
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Jesse Open
 
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Nearing 45 degrees, methanol vaporization is becoming difficult.
Old 01-16-2021, 04:51 AM
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Thanks for the reply back. I'll try again when the weather gets a bit better.
Old 01-16-2021, 06:27 PM
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Originally Posted by ahdofu View Post
Do you see a change in the peak RPM of a glow engine in cold vs. warm days? In summer time this particular engine of mine was peaking at 9400 RPM (OAT ~ 75 degs). Yesterday it reached 8900 RPM at OAT of 50 degs. On one hand the higher density of air affects the power needs of the prop but then the higher air density should also help the motor as well. Anyway I was wondering what folks have experienced. BTW this is an OS Surpass 91P glow engine using a MA 14x6 prop with Omega 18/15 fuel.
yes !
the colder the air is the richer you need to tune

Jim
Old 01-16-2021, 07:07 PM
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Jesse Open
 
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Originally Posted by ahdofu View Post
Thanks for the reply back. I'll try again when the weather gets a bit better.

With a low temp, methanol fuel won't start by itself. We used to preheat the engines and give a shot of ciggy lighter fluid down the carb. They would run but fussy and fuel draw became weak.
Power was down indeed.
Old 01-16-2021, 09:25 PM
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It gets REALLY interesting on days when it is -5F or -10F. But no issues with overheating, or having humidity factor into the power equation.....

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