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Engine basics => Engine set up tips => Topic started by: phil myers on November 09, 2012, 04:53:31 AM
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I've noticed in my three years of model flying that as the temperatures drop at this time of year say, from 25 c in the middle of summer to 10c now I have to richen the needle (2-3 clicks) to get similar runs.. obviously air temp is the issue but can someone tell me what is really happening, just curious.. Thanks
Phil
Norfolk . England
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Phil when the air is cold it usually contains more oxygen. Your engine is taking in more oxygen and to keep the mixture the same you have to add more fuel thus explaining the richer needle setting. This will usually result in slightly more power. Just the opposite hapens when the air is hot. Hope this helps.
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Thanks Mike! H^^
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Phil when the air is cold it usually contains more oxygen. Your engine is taking in more oxygen and to keep the mixture the same you have to add more fuel thus explaining the richer needle setting. This will usually result in slightly more power. Just the opposite hapens when the air is hot. Hope this helps.
That's part of it, the other half of the story is that the viscosity of the fuel goes up when the temperature goes down, so you have to open the needle just to get the same fuel flow rate for a given amount of suction.
Brett
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Thanks Brett H^^
Phil
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Don't forget that good warm and freshly charged batteries are your friend. Also Naptha or Ronson-like lighter fluid. y1 Steve
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The lighter fluid does indeed work well. Just use a glove if your not already doing so as sometimes it does want to kick back. Last year I got my finger whacked pretty good doing the lighter fluid trick. The Rev-up prop broke over my finger. I have to tell you, I think everyone nearby learned some new words that afternoon. Ken
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The lighter fluid does indeed work well. Just use a glove if your not already doing so as sometimes it does want to kick back. Last year I got my finger whacked pretty good doing the lighter fluid trick. The Rev-up prop broke over my finger. I have to tell you, I think everyone nearby learned some new words that afternoon. Ken
And it hurts 3x as much when your finger is already cold. I can assure you that when the same thing happens with a PA61 and an Eather prop, it doesn't break the prop. For whatever reason, my last PA61 was absolutely evil in cold conditions. It had no problem starting, it even started with the battery off at less than 50 degrees. But the kickbacks were brutal. Other nominally identical engines were not nearly as bad.
Brett
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I have to give my Briggs & Stratton (pressure washer) a shot of ether from a spray can to get it going. I wonder if that would work in a glo engine?
Floyd
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Hi
I have learned to be very carefull with bigger engines, I don't use anything else than the fuel I use to prime the engine. Especially with wooden props/dural prop fastening screw.
In colder weather it's all about a good glow power and correct amount of prime.
On the other hand, I've never used a starter, chicken stick or even a glove.
But, my engine runs clockwise.
L
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Note to Ty. I will not try it! I really haven't had any issues starting glo engines.
My Allis-Chalmers diesel tractor has glo plugs for easy starts.
Floyd
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Its funny how some engines start fine when its cold and others of the same make and model can be cantankerous to say the least, I have an old Fox .35 1958 or so with the spade needle valve and its a great starter and runner even when its cold out. I have a Veco 19 bushed engine that turns into an evil ax murderer below 55 degrees or so but my 19 bb's are pussy cats . My 68 fox with hemI kit is an easy starter but my mid 70's .35 stunt won't be back out till it gets warmer. I gotta pick up some zippo fuel and try that. T.J.
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I have to give my Briggs & Stratton (pressure washer) a shot of ether from a spray can to get it going. I wonder if that would work in a glo engine?
Floyd
Yep, they actually sell this in a pressure can here in Oz, its called 'Start You Barst*rd!.'
And glows plug engines being semi compression ignition engines should be able to use it, since all you need is compression (or more precisely the heat from compression) to trigger it.
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And I have just stumbled upon this gem!
"But there were other problems, to wit, the
temperature. Our small, mostly aluminum
motors needed heat to start, so by definition,
they were never designed for winter
running. One common means of generating
heat to start them was to wrap a tiny strip of
rag around the cylinder, pour engine fuel on
it, and set it afire. Usually this worked ok
provided you paid close attention to what
was going on. You see, the alcohol these
little motors operated on had no visible
color when burning. The only warning you
had that things were amiss was this quickly growing brown spot on the model that wasn’t there
when you built it. This meant your model was on fire!"
https://docs.google.com/viewer?a=v&q=cache:CLpshjVoMOUJ:https://www.modelaircraft.org/files/DahlkeDouglasA.pdf+super+saucer+control+line+model&hl=en&gl=au&pid=bl&srcid=ADGEESgS9Nhjvk6npgPjucYH2M-cDC8MKimqK005gFirmwkbJOedJmjww1kL9xuQhjBAgJ7IB-rk6B3qtv9oFW-k2gIUxseCb4o-BFJ2fh512RKhYBvi7SuxATBxGNPXICHrpNxh7vsh&sig=AHIEtbTBiki5M-UJKTcqrJWH-LPNwuW0Kg
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Well I hit the hardware store on the way home and picked up a tin of Red Devil lighter fluid . I mounted the old veco .19 ln the stand gave it a prime and lo and behold it started on the second flip thanks for the tip guys it worked great. My propping finger and backup propping finger thank you :) T.J.
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I was trying to start a car that had stood for 9 months last very cold and icy winter. Battery was kept trickled charged, the engine was just on the verge of firing, so I used a can of ether based spray for starting recalcitrant engines. It killed the engine stone dead and it didn't return to its previous state until all the ether had gone through the engine! Never did work that one out!
Andrew.
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I was trying to start a car that had stood for 9 months last very cold and icy winter. Battery was kept trickled charged, the engine was just on the verge of firing, so I used a can of ether based spray for starting recalcitrant engines. It killed the engine stone dead and it didn't return to its previous state until all the ether had gone through the engine! Never did work that one out!
Andrew.
Did you check the comp?
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Andrew...A little dab will do ya! Don't empty the can into the engine. Also don't get the air filter wet with it, because if it's paper, any dust on it will turn to mud. If the filter is an oiled foam-type, it will wash the oil off the filter and into the engine, also not good.
Best to remove the air filter, regardless of what sort. H^^ Steve