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Discussion Starter #1
What would the interest be in a 3 position gas valve that has the regular and the 'dirty' positions, like the OEM, but also includes a 3rd position that vents excess, for use with suppressors?

I recently started looking at just replicating the OEM, as they are out of stock everywhere, and had the crazy thought about a suppressor setting.

Thoughts?
 

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Do it Art! However I was always under impression the OEM's two positions were for normal and suppressed not normal and "dirty".
 

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Without a can, I ran the 2 position normal and adverse.
 

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Do it Art! However I was always under impression the OEM's two positions were for normal and suppressed not normal and "dirty".
Correct...2nd position has vent holes that line up with the gas block vent channel (see pic below...ignore the red circle for the gas jet...the vent channel is in front of the gas block...about 2mm in length and 1mm in width...)...2nd position is NOT an adverse/dirty condition setting...it is to vent excess pressure once a can is on (well the OEM approved can that is)...

Problem with the OEM is that the gas plug gas control size is actually the same (minus the two small vent holes)...thus why the MotoTech 3 position gas plug is so good because it starts with an OEM size and gradually goes down in size (however I do not believe it utilizes the vent capability of the OEM gas block's machined vent channel...
142247

142248
 

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Correct...2nd position has vent holes that line up with the gas block vent (see pic below...ignore the red circle for the gas jet...the vent is in front of the gas block...about 2mm in length and 1mm in width...)...2nd position is NOT an adverse/dirty condition setting...it is to vent excess pressure once a can is on...
View attachment 142247
View attachment 142248
Well damn TH, I appreciate the backup and clarification. But Man, I surely didn't want you to cross-saw you SCAR's barrel and gas block to prove a point though.
 

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Discussion Starter #13
I thought military SCARs were different from civilian, in that mil 2-position were normal and suppressed (for regular and higher port pressure), while civilian were regular and adverse. However this is not a subject I had researched closely. I got into it just because I saw someone post about losing their valve, and MDW is out of stock. I'm working with a high end metal 3D print company who have a few employees and management who are very gun friendly, so I designed it in CAD, just to get an idea of pricing. In the process, my mind went in the direction of 'what if'.

Pressure in the gas system is driven by the accumulated flow resistance of the way in, and the accumulated flow resistance of the way out, plus ammunition choice and if you are suppressed or not.\

Gas flowing into the gas system is limited by the gas jet diameter, and by the diameter of the larger inlet hole in the gas valve. Gas flowing out of the system is limited by the central hole in the valve, and the size/position of the two small supplemental holes in the gas cylinder. Changing the gas jet size, or the central hole, will impact all settings, while changing the larger inlet size or the size of the supplemental exhaust openings impacts only that one setting. Obviously, ammo choice and use of a suppressor impact the pressure of the gas coming in as well, which is why we are having this discussion.

If the Mototech solution meets the need, I won't likely do anything, because I don't like doing 'me too' products. Unless I can add an innovation that improves it, I won't do it. However I can think of several changes that 'may' offer a benefit. I can do these in inconel or titanium, though I'm not aware of gas erosion being a problem, so I'm not sure that is a benefit, and it raises cost. I could optimize hole sizes for the 3 settings, though I'm not sure how to quantitatively measure the results - I need a piezo pressure gage and am not sure how to mount it without affecting the port pressure, or without having to drill holes in my rifle. I thought about adding replacable jets to the inlet or outlet of the valve, so you could tune it, but I'm not sure how many people could or would properly tune.

That's why these forum discussions are useful.

Art
 

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Might want to check if Mototech and Eddie have patented his. If so, I don't think that there is anything you could do to your version to get around his patent. His is pretty damn good as it is.
 
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