Most are only single polarity - the mini uses a specifically designed noid that is low cost, but high quality and functions using some very interesting magnetic circuit stuff.
I tend to think of dwell as a gate opening (it isn't 1:1 with the actual valve, but directionally it's the same.)
So, you need some AMOUNT (mass flow) of air to move your bolt or whatever, right?
So, when you have longer to deliver the amount (more dwell), then at any given time you don't have to be flowing AS MUCH air to get to that volume or mass in the longer dwell period. This translates into lower LPR pressures. With less pressure at the noid (because we're running a lower dwell) you are decreasing the volume flow, and because it can't fill the space behind a ramas quickly, the assembly accelerates more slowly and with less jerkiness. That's why the Intimidator Eigenrams have added 2ms of dwell in the manual since 2006.
Shocker Eigenbolts are a bit different - they're actually pretty dwell insensitive, but since it vents the "spool/ram" section of the bolt, it saves air to not overdwell it.
Eigenrings are very complicated to explain, but basically the ring keeps the chamber pressure high, which keeps the forward biased force on the bolt higher longer. By not holding the bolt forward, you're able to save more air in the chamber than you can otherwise, because the bolt's actuation is crisper.
With the mini, the open dwell (basically the amount of time air is flowing) will help move the bolt and degas the area behind the poppet. really overdwelled settings along with velo adjuster settings over 1.5 turns out from all the way in will result is terrible efficiency because the poppet will be trying to close by flowing through the bleed hole, but the noid is not letting the closing pressure build. A minimized dwell and a backcap of 1 to 1.25 turns will result is really excellent efficiency with the eigenbolt.
http://www.techpb.com/forum/index.php?s ... &p=3101518
If you have time, I would like more explanation then that. I understand that as the chamber is venting, it creates a vacuum on one side of the Eigenring and pulls it to the back cap. I can understand how that would work as a way to cut off some of the air flow towards the end of the bolt's cycle (which was unneeded), but I don't understand how the ring keeps the pressure in the chamber higher during the shot. It seems to me, that as the ring moves, pressures on both sides will stay more or less the same, therefore, if pressures are the same, then, the output pressure of the bolt's chamber should be the same as well. If anything, I would think that the pressure on the side facing the back cap would be lower then the other side, because, it's dragging across the top hat in a race to equalize and it can't move at the exact speed necessary to equalize do to the force of friction exerted on the interior o-ring.
I'm, fairly, certain that you know this, and I'm missing something... obviously, I would like to know where I'm wrong.
http://www.techpb.com/forum/index.php?s ... &p=3101656
You kind of have to think about it in discretized steps for it to make sense. Imagine infinitely small time steps or motion steps
1. valve begins venting
2. pressure due to venting causes a pressure difference due to the ring being a large restriction
3. pressure difference causes the ring to move towards the backcap in an attempt to equalize - forget the leakby in the ring as it's not significant at the timescale of the shot itself
This motion can be though of best as an energy gradient - the air behind the ring wants to get out, but it instead drives the ring backwards, which shrinks the volume of the main chamber, and essentially dumps the energy behind the sail back into the chamber air by piston action.
Because of the in the system that drives this action, the pressure should stay higher than it otherwise would, and then drop much more quickly due to the decreased final volume.
I don't know how much of this is accurate, but I've run through it with some very smart people and I have a lot of at least anecdotal data confirming that this TYPE of effect must exist (not just efficiency, but claims of drop in velocity INCREASE, as well as the ability to lower dwell after drop in, which jives with more average forward bias force from the fuse bolt geometry)
http://www.techpb.com/forum/index.php?s ... &p=3102094
