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Engine basics => Engine set up tips => Topic started by: Kim Mortimore on August 17, 2007, 11:22:38 AM
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If you fly in relatively cool, wet morning air, and then fly again in warmer, dryer afternoon air, which run is longer? I can never remember this. Asking in relation to fuel management at a contest.
Thanks,
Kim Mortimore
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If you fly in relatively cool, wet morning air, and then fly again in warmer, dryer afternoon air, which run is longer? I can never remember this. Asking in relation to fuel management at a contest.
Thanks,
Kim Mortimore
HI Kim
Typically The runs are shorter in the cooler morning air and longer in the warmer air. Also normally if the morning air is wet the afternoon air is also very humid, both heat and humidity will make for longer run times . as you need to lean the mixture in those conditions with all else being equal
Regards
Randy
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Randy Now what Kim asked is good but what about the weather and and % of Nitro / oils with temp?
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Randy Now what Kim asked is good but what about the weather and and % of Nitro / oils with temp?
I'm not Randy but Heat goes up use more nitro. The engine makes more power in cool air = less nitro. Same oil content. I use 20% oil for PA's
EDIT More nitro means you will have to open the needle valve up. So you will have to use more fule.
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Also, keep in mnd where you are...
Most of the contests I can get to are in Tucson, AZ. Altitude above sea level is ~ 2000'. My home altitude in Sierra Vista is nearer 5,000'. Early morning flights in Tucson, in denser air, seem to be 'leaner' than afternoon flights. Temperatures go up, humidity goes down, in deserts. With Fox 35s as an example of an engine that, once set, doesn't need tinkering, in Tucson, at most contests, the later flight in the day DOES reuire leaning a click or more. That's a bunch for a dialed-in Fox 35.
At sea level, or at altitudes and climates where temp and %Rel Hum stay closely related,the situation can be very different.
Fly for where you are... And, if in doubt, check it out. That's what practice flying is for. At worst, you may find that YOU will have to adjust to conditons - turns are looser; bottoms sink after leveling - or vice versa: Turns pop out higher than you expect, and bottoms are higher...
YOU are flying the model; YOU may have to put it where the air you are in dictates.
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Randy Now what Kim asked is good but what about the weather and and % of Nitro / oils with temp?
Hi Larry
There are dozens of differant setups, here is mine, When the weather is cool , or when I am in the cooler months my engines setups are normally running 5% nitro, as the heat or hotter months come in I go up to 7.5% or to 10% IF IT REALLY GETS HOT.
At the NATs this year I was running 7.5 % nitro and dropped to 5% when it got a little cooler.
This way for me I don't normally need to change anything but the fuel. I also have many people using my setups doing the same. It works, and works very well.
Another example is when I went to places like Lubbock I had to go straight to 10% to get similar performance that I had in Atlanta with 5%.
I could very easily setup for base 10 or 15% nitro but that would mean I would have to go to 20 or 25% in hotter months, or have to change prop/venturie/head shims much more than I would normally,That is not wanted or necessary.
I don't have to up oil percentages, I most always just use 21 % oil in the PA engines, 25% oil in STs 46,51,60, 26% in FOXs, and 23% in Aero Tigers and Magnums BB engines. AS always you may have to adjust something for your conditions
Regards
Randy
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Randy,
Do you count Aero One content as part of the oil percentage, or is it in addition to the oil % ?
Thanks,
Kim Mortimore
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Randy,
Do you count Aero One content as part of the oil percentage, or is it in addition to the oil % ?
Thanks,
Kim Mortimore
hi Kim
Yes I count the AERO-1 , example I use 20% in my PAs and add 1% Aero-1
regards
Randy