LP and HP and Gas Efficiency

[Klay01]

Alright, I've heard from different sources that HP is more efficient than LP. But it makes sense for a LP gun which uses less air to be more efficient? Hmm.. can someone clarify this?

Also, my friend CDAWG said that when an automag is fired.. the pressure that actually goes onto the ball is somewhere around 80psi.. if that is true then wouldnt an automag be considered a LP gun? Hmm questions questions questions...

[Cypres0099]

I'm pretty sure that LP or HP makes no difference as to efficiency.

I thought the pressure behind the ball was around 60 psi, maybe I got mixed up. To classify a gun as low pressure, I don't think they use the pressure behind the ball. I think it's the regulated pressure inside the vavle....?

Also, according to Glenn Palmer, I think the automag is a low pressure gun.

[ezrunner]

each design (cocker, mag, spyder, etc)
has a "sweet spot".

This is found by changing out springs and valves and seats and seals until your head explodes.

All the while you are testing at various pressures.

Some designs are more efficient at higher pressures, some at lower pressures. It is a side effect of the design and air flow paths.

I don't think any one blanket statement can be made as to which is always more efficient. Both can be setup really well or really badly.

-rob

[einhander619]

The point of LP is so you can use more of your tank's fill. That is the main drawback of a mag, RT valves like about 900 in order to really rip, below that they get progressively mushy.

When setting up one's gun, the goal should be to make it as efficient as possible, but what most people do is simply aim for the lowest input pressure possible. Wrongo! Lower Pressures will come about naturally as a result of the gun needing less air pressure to function(due to smoother surfaces, tighter tolerances, bigger air passages, lighter springs and moving parts, etc.)

[athomas]

einhander619 said it well.

Further explaination.

All guns are fairly low pressure guns. The behind the ball pressure is anywhere from 30 to 120 psi. Depending on your valve setup, barrel length, porting, inside diameter, etc, you will get diffeerent efficiencies. An autococker is on the high end of the scale here and is fairly efficient. An Automag is in the middle and its efficiency reflects that.

Too low a pressure and the ball takes too long to accelerate and the area behind the ball requires too much air to maintain pressure. This air is wasted once the ball exits the barrel.

Too high a pressure and you can't provide an adequate delivery system. You can't use enough of the air in a tank, or you put additional strain of parts of the gun or ball.

The input pressure that a gun runs well at is another story. Different guns use various methods of delivering the air to the ball and to operate the pneumatics. Many people refer to this when they talk about a gun being low or high pressure. However, this is only the ability of a gun to utilize more of the air in the bottle and in no way reflects the efficiency of the operation.

[Kevmaster]

Here is a graph i made for the rainmaker. it applies to ALL markers, its just that the numbers at the bottom may be a little different:
http://www.samuraiforce.net/images/efficiency.gif



hope that helps explain things a little

[AzrealDarkmoonZ]

Cut n Pasted from another topic, on cocker valves.

First a little thought of my own over at air-powered.com, worth a read to better understand my platform. About a 1/3 of the way down you should see a phrase "Some Thoughts:"

http://www.air-powered.com/forum/cgi-bin/ikonboard/ikonboard.cgi?s=3e4bcaaa2eb7ffff;act=ST;f=17;t=323 5



Airflow really is the key, moving as much air in as little time, that being said the new stock valves are better than some of the aftermarket valves. I prefer the use of the Red Valve, having used a 99 stock, palmerized valve, 2k stock valve and tornado.

Notice the valve stem compared to the stock valve on aftermarket valves, this allows more air through the valve in a shorter space of time, also the internal milling of the valve can also hinder air flow, you want air to expand as little as possible and not be restricted until it hits the ball. Its also important to try to match bolt size to valve outlet size, although this is generally not a problem. Some valves claim to have a bigger inlet hole but this runs into the problem of the area that the air must flow through to get to the bolt, that being the whole in the body, the merlins actually enlarge this so that they can have a larger inlet on the valve and not lose the flow. Really a turned down stem, and better internal milled valve is the best way and the way your good valves achieve greater efficiency.

Also in reference to PROs claims, I have yet to here anyone not affliated with PRO able to reach the efficiency they claimed, although recently they have changed their claims a bit, 2000+ shots on a 68/45 which is attainable if somewhat difficult. Also PRO neglected to mention when did FPS fall below acceptable range, was it 250? 200 or what?

Az

www.air-powered.com

[Bront]

Most valves have 2 issues. How much volume they let through per second (Or any other time period), and how long they stay open. The idea is to get the least amount of total air needed through the valve in the quickest amount of time. At lower pressures, often the valve is left open too long, as well as there simply is not enough force to efficiently opperate the internals. At higher pressures, there is to much air and some effort is wasted. Also, with the valve timing, you may get extra air in the system if the valve is open too long.

I'm more familiar with blowbacks than any other marker, and I know that if you replace the valve with a high end valve like a Madman Rocket Valve or AKA Tornado valve, you can shorten the time the valve is open considerably due to the increased flow through, and the increased flow is more efficient than the old valve at similar pressures.

Reducing the work the air needs to do allows you to decrease the ammount of air being used. So things that make a marker lighter, like a Delrin Bolt or Titanium striker (In the case of a blowback) can help increase efficiency by reducing the need for that much air power (AKA, the air works smarter, not harder). There are ways to do this in most markers.

With a mag, you're kinda stuck with what you get. Other than a Level 10 (Which decreases efficiency), I don't know of too much that does effect efficiency assuming you properly maintain it (Worn parts probably effect it a bit, but that's part of maintinance).

[athomas]

I'm willing to bet that if you measure the behind the ball pressure of the mag with the level 10, you will find that it is lower than with the level 7 bolt. The bolt probably stays forward longer and the airflow is more restricted due to the higher tension on the spring.

It comes down to the free flowing of air from the chamber to the ball. Cockers are good at this because of the open airways.

[Havoc_online]

peak pressure is just a tad higher on level 10 mags over level 7. This is to make up for lost bolt speed.(L7 bolt speed is around 20fps, LX bolt speed is around 16-18fps in the second stage)

[athomas]

What is the behind the ball pressure of a level 10 mag? Does the peak pressure drop off quicker due to the stiffer bolt spring?