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|10-11-2010, 01:47 AM||#6 (permalink)|
Join Date: Jun 2008
typically when you install one, without changing ANY of the other settings on the gun, it makes your velocity jump up 30+ FPS
Which means you need to lower your pressure (spring or air pressure) to get your gun back to 300fps
Also, lower pressure guns tend to be quieter, due to the lack of the supersonic "crack" of the air going through the valve. Also, it is widely believed that low pressure guns are gentler on paint.
Quite a few guns have "low pressure" valves, Vice, Ego, along with Spyders
So in a nutshell, it's an upgrade for your gun... BUT will require some additional tuning past the simple installation to allow your gun to take full advantage of it.
|10-11-2010, 12:41 PM||#7 (permalink)|
Join Date: Jun 2008
^^ I was more talking about the "upgrade" part in itself, not so much low vs high pressure guns. A Mini is pretty loud for a low pressure gun, but compared to a Tippmann (high pressure), it's pretty quiet.
It sounds like his question is in regards to an upgrade for a particular gun. Some of the guns that I've replaced "High Pressure" valves with "Low Pressure" valves tended to be quieter at the same velocity.
Autococker - replaced the stock High Pressure valve, with a Check-It Low Pressure Valve, the gun appeared to be quieter at 300fps
Ego - take out the stock low pressure valve, and install the high pressure valve, and it appears to get louder
Vice - replace the stock high pressure poppet, with the low pressure poppet (it just has a slightly longer stem) and it appears to make the gun quieter
Spyder - take out the stock high pressure valve, and install a regulator and a "low pressure" valve like a tornado, AKA or Magna Port, and it appears to make the gun quieter
Ego's operate at about 220psi, and they are easily some of the loudest guns I've ever shot. I will say that there is something about the little oring that Bob Long puts on the back of the poppet shaft that seems to do some magic.....
|10-11-2010, 05:34 PM||#8 (permalink)|
Join Date: Oct 2007
All valves have sonic flow. Generally supersonic. If the operating pressure is above 30 psi (reasonably close to critical for choked flow conditions in an orifice system of dry air), it's going to be at sonic velocity in the throat of the valve, and supersonic if the valve diverges beyond the throat (hint: they all do).
The sound signature is more a result of the amount of gas leaked down the barrel- in many guns, the dwell (duration of valve opening) is effectively constant. In low pressure guns, the higher flow usually means lower dwell is needed. If the dwell is constant, then the lower pressure means less total energy flow. Less energy means less pressure gradient at the muzzle, which generally is less sound.
However, any gun can be tuned to be quiet or loud if carefully balanced.
"Low pressure" valves are, more often than not, simply a mislabeled "high(er) flow valve". Which can be a good thing, or a moot point.
Bob Long's guns are quieter for several reasons, not the least of which is the valve diameter, with valve stem shape and laminar spoilers having a significant effect as well. I inspected the valve bodies on several guns before determining which to buy, and the orifice diameter strongly correlates (inversely) with the sound signature for otherwise similar designs.
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