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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> Heat and humidity effects on a glow motor.
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Heat and humidity effects on a glow motor. - 7/3/2003 4:41:28 PM   
Zpat



Posts: 558
Joined: 11/9/2002
From: Lima, OH,
Status: offline 		Can someone please explain to me how heat and humidity effect a glow motor.

Having flown gas for a number of years, I'm completely at a loss on tweaking the needle on a glow motor every time there is a difference in temperature and humidity.
       Post #: 1

Heat and humidity effects on a glow motor. - 7/3/2003 8:04:00 PM   
gubbs3



Posts: 1403
Joined: 12/8/2001
From: Coon Rapids, MN, USA
Status: offline 		Once you get a grip on the basics tuning becomes very easy. To explain what you need to do for heat and humidity you need to know that warm air is less dense so it carries less oxygen. The same with humidity. Believe it or not, humid air is less dense than dry air. So for both situations, you would need to run a leaner mixture than on a cool dry day. You will notice a loss in performance which there's nothing you can do about short of running 30% nitro.

(in reply to Zpat)
       Post #: 2

Heat and humidity effects on a glow motor. - 7/3/2003 8:29:58 PM   
Zpat



Posts: 558
Joined: 11/9/2002
From: Lima, OH,
Status: offline 		Gubbs3
That is exacly the problem I have.
After I lean the engine to compensate for heat and humidity, the power falls off.
Last night was a perfect example. After leaning I went into a hover and the motor quit.
Needless to post the results.

(in reply to Zpat)
       Post #: 3

Heat and humidity effects on a glow motor. - 7/3/2003 11:26:15 PM   
Homebrewer



Posts: 1335
Joined: 12/29/2001
From: Colorado Springs, CO, USA
Status: offline 		There is no need to worry about whether to richen or lean the engine depending on the temp and humdity changes.

All you gotta do is use the pinch test. Start engine, run to full throttle and pinch fuel line and relase. If engine speeds about 300-400 rpm it is set perfectly. If not adjust as necessary so this occurs meaning if it dies or doesn't speed up at all, then it is too lean and you need to richen a little. If it speeds up too much then lean it out a bit.

If you can't reach the fuel line to do pinch test than a tach is your best bet. Fire up engine, go to full throttle, and while reading tach lean engine to max lean rpm (you can do this by sound also). Once at max lean rpm, use tach to richen engine by about 300-400 rpm. Once done you are set for a good portion of the day's flying.

Andy

(in reply to Zpat)
       Post #: 4

Heat and humidity effects on a glow motor. - 7/4/2003 12:11:57 AM   
RaceCity



Posts: 1842
Joined: 7/10/2002
From: NotUpNorth, USA
Status: offline 		Understand, that with any normally aspirated engine (ie: non supercharged/turbocharged) engine...there is NO way to compensate fully for the effects of higher temps/humidity.

As a pilot who earns his living in this regard....

You can lean "to a point". Best case scenario, you reach on optimum setting. This will most likely NOT be "peak" as it was let's say....last December.

All aspects of A/C performance decline in hot, humid weather. Since the air is less dense....the PROP is less efficient. The WING is less efficient, and the ENGINE makes less power.

It's a fact of aviation.

'Race

_____________________________

AMA 63990

(in reply to Zpat)
       Post #: 5

Heat and humidity effects on a glow motor. - 7/4/2003 2:19:35 AM   
Zpat



Posts: 558
Joined: 11/9/2002
From: Lima, OH,
Status: offline 		Homebrewer,
When I do the pinch test at high rpm and back it off my transition period seems to suffer.

Most flying is done at 1/2 throttle or less and full power is only applied in vertical manuvers.

My best luck so far is running on the rich side at high rpm. This seems to keep the engine cool in the vertical.

I've got to the point where my transition is livable, slightly rich.

It seems I have to tweek the needle on a daily basis, I don't know if this is common on glow motors.

A lot of guys just fire in up and go but they usually fly in big circles, as opposed to flying close in.

I'm going to experiment with glow plugs and props next. I'm just having a good 'ole' time.

RaceCity,

You're so right!

There was less of everything. Less power, less stability, and the biggest less of all was altitude.

Maybe I'll have it cured the next time.

Thanks Guys!

(in reply to Zpat)
       Post #: 6

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