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Do Pcp's Use More Air When Its Colder

Discussion in 'Anything Airgun Related' started by Blister, Dec 2, 2019 at 2:31 PM.

  1. Blister

    Blister Busy Member

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    i have found that my uragan is using more air per shot then usual is it due to the wheather being colder
     
  2. squib

    squib Posting Addict

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    For a truly full 300 bar bottle, for every 1degC fall in temp, your bottle will loose approx 1 bar/Degree C

    F2ACCF43-EFB0-477F-9D6F-64AECCC77202.png
     
  3. Blister

    Blister Busy Member

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    @squib
    i will have to buy a coat for it then
     
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  4. Paul M.

    Paul M. Engaging Member

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    Yup, fill your rifle indoors and you might lose 6 or 7 bar taking it outside due to temperature. Each shot though only uses less than 1% more air by mass.
     
    PumpnGun likes this.
  5. charlie1969

    charlie1969 Engaging Member

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    Is that the same for regulated rifles?
     
  6. Wewekokowe

    Wewekokowe Engaging Member

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    The answer is no but it will make less power.
     
  7. jesim1

    jesim1 Very Active

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    The answer is yes, as although your gun it has the same volumetric size in both warm and cold weather, the air in cold weather is more dense, and as we use it under pressure this has the effect stated above of using just that little bit more ;)
     
  8. Bezzer

    Bezzer Busy Member

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    Sorry I don't understand that. It's a closed system, the temperature is the same either side of the reg so filling from the cylinder to the reg between shots would use the same amount of air from the cylinder whether cold or hot?. Yes it would be denser if colder but it's still the same volume and (reg) pressure so wouldn't be using "just that little bit more" surely.
     
  9. BallisticBill

    BallisticBill Busy Member

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    When you fill the cylinder you will put in a certain mass; for a given pressure the mass will be higher if it's cold. Once you've filled it the cylinder pressure will increase/decrease if the temperature is higher/lower. The reg will operate at a fixed pressure irrespective of temperature so will let in a fixed volume, but more mass if the air is colder (= more dense). So if the temperature falls, you let more mass into the plenum each shot and the cylinder empties quicker. Same with an unregged gun, more air mass will go into the transfer port for each shot. This might suggest you will get less power at high temperature but the reduced friction in the action more than offsets the reduced mass of air.
     
  10. Squintykid

    Squintykid Busy Member

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    as above...too slow

    yes, the reg will operate at the same pressure but if you fill at home ie 20 degrees c and go outside into for example 0 deg c the density will change the commpessed air 'shrinks'. hence you lose 1 BAR per degree....a 20 bar drop. and therefore get less shots.
    The volume of regulated air is relative to the ambient temperature so the released air still gives the same performance

    The opposite to leaving a sealed plastic bottle in the sun and the air expanding with an increase in pressure.

    A 0 deg fill will increase by 1 bar, 200bar will become 220 bar when the gun is at 20 deg, the reg will still operate at its set pressure.
    if the reg holds 100bar at 0 deg and warms up then that first shot will be at the higher pressure before normalizing
     
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  11. Bezzer

    Bezzer Busy Member

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    I wasn't querying that, I was on about using "just that little bit more", taking it was on about per shot not per fill.
    I've never found my regged PCPs give the same performance in colder weather they always drop in power as it gets cooler to the degree that I've got a cold and warm set of internals - hammer springs and spacers- that I use at different times of the year. I've heard plenty of HFT shooters say the same, they like to keep their guns at what they think is their optimum fps and are always on about turning them up and down according to the temperature. Going the other way I also know of people failing the chrono testing in warm weather with a regged gun, that's over 3 shots so it isn't just the first one in the reg. One in particular was well over and after the shoot was tested again and they couldn't get it to register over at all, turns out it was in the sun just before the official test then had been shaded until tested later.
    So I don't see how you can say the released air gives the same performance.
     
  12. jesim1

    jesim1 Very Active

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    If you think about it this way:

    You know a 12L 300bar fill when warm will cool to say 270bar - agreed?

    You also accept that the air has not leaked out - it's still in the cylinder, but now it's colder it is more dense - still with me?

    So by the above facts, you have to come to the conclusion that you will get less shots from a 12L cylinder 270bar cold, than from one that's 300bar warm - I hope you agree.

    It therefor follows that the cold cylinder has to be using more gas by mass (not volume) when compared to a warm cylinder as you get less shots, it's just that the cold ones air is more dense.

    So...……………….…given that this is true of any size of cylinder and for any UK weather conditions your gun will use - wait for it...………………………... "just that little bit more" air than when it's warm :thumb:

    James
     
  13. Squintykid

    Squintykid Busy Member

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    hahaha, Blister not Bezzer, must wear my glasses.

    wow two set of springs, doubt the OP is that concerned?
    Just wants to know why he's losing shots when he's out in frosty weather and his dive bottle is emptying quicker?

    would hazzard a guess at barrel and internals contracting, valve stem pip hardening? a miniscule squeeze creating more friction?
    Big thread on it last year, technical qoting of AGW? article. Big issue was springer 'cold tunes' exceeding the limit by 0.75>1 ft/lb in warm weather?

    As you have two sets of springs and spacers you would understand range chrono fails...hot tune, cold tune as above.
     
  14. Howlin Wolf

    Howlin Wolf Busy Member

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    Pressure is directly proportional to temperature.

    Increase temperature = increase pressure.
    Decrease temperature = decrease pressure.

    The number of molecules remains the same.
     
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  15. TonyB55

    TonyB55 Engaging Member

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    Does this mean instead of 120 shot per fill I might only get 115? Does it matter that much at all?
     
  16. Blister

    Blister Busy Member

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    so we would be looking at a lower fps when is cold and higher when is warm
     
  17. jesim1

    jesim1 Very Active

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    :thumb: - As every HFT and FT bod will tell you, it's half the reason they miss a 45m shot according to them :D
     
    Wewekokowe likes this.

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