A balanced poppet is a special type of valve that uses air pressure to "assist" the opening of the valve. Normally, the valve hammer has to fight against a huge force of air pressure on the valve's other end in order to get it open (fire the ball). When the valve is balanced, air pressure pushes the valve in both directions, both open and closed. This means the force needed to open it is MUCH less, improving cycline time and consistency, decreasing air consumption, as well as other theoretical benefits.
With the proper modificaiton, valves like this can be installed in any hammer/valve based marker. I've retrofitted them into some of my own guns, detailed here. I didn't mess around with this unless it was really "worth doing".
Impulse:
The valve in an Impulse has a few possabilities for this type of modification. At one point LuckyPB released an upgrade valve to do the task, but it was short-lived due to lack of interest for Imp upgrades in 2006. I decided to build my own version of the valve by fabricating a new sleeve to be inserted in the endcap, which would fit around the new valve poppet's balanced section. The disadvantage to this is that it reduces the amount of air available to fire the marker, but it's probably fine so long as not removing too much volume. Below you can see my modified valve endcap using an inside sleeve:
Now for the fun part. The new valve and balanced end have to be functional with the existing parts, unless re-making the endire valve is the idea (not the plan here). Pictured below is the final balanced valve, threaded together with a 6-32 threaded rod. The second and third pictures were taken during the fabrication of the balanced section and valve poppet respectively.
The last step is to make a new hammer. There's no longer a need for a heavyweight steel or brass hammer; at this point the only job of the hammer is to hold onto the bolt pin. I made a new one out of aluminum:
The valve is fitted with a small spring at the endcap side in order to keep it closed (seen in the above pictures). This is the only pressure the hammer must overcome to fire the marker; it's only around 8 pounds in this case, instead of the stock valve which requires 80 POUNDS! The end result is a marker that operates with a solenoid pneumatics pressure of 60-psi, on a dwell of 7 milliseconds.
Nerve:
Balanced valves in Nerves have even more benefits than in Impulses, however they are significantly more difficult to correctly impliment without creating a total hack-job install. This mod is finished and functional, but it could be better if I revisited the design (the version below was very hard to fabricate). I would love to make a replacement for this but due to the discontinued nature of the marker I probably won't be able to find the time.
The mod involves a new valve extender which contains the new functional components. Here's what mine looks like:
As with the Impulse modification, the hammer can now be much lighter and only needs to hold the bolt pin.
It's possible to simplify the install by mounting an LPR on the vertical adapter and instead making a "regular" valve endcap like that of an Impulse/Bushmaster/Angel, that doesn't use its own integrated LPR. I didn't want to do this because it wouldn't be marketable due to the cost of a whole new LPR and such. The exact internal configuration I made can be seen below...
If anybody wants to expand on this concept then be my guest!