Before I begin...Many thanks goes to Dave/ @sb327 for his contributions in getting me to where I am today with my current valve arrangement, we worked together closely to dial in versatile pilot valve that works very similarly to the one found in the L2. Also thanks to @csdilligaf for turning me out another one for me for my unregulated marauder. He is a fine gentleman and a machinist whose work is impeccable, honestly out of this world, at this level its an art. The one he turned for me is shown below anodized in a light gun metal grey. Starting from the Bottom, are a series of poppet valves found in todays pcp's, as we work our way up, the valve designs become more complex but overcoming the force holding the valve shut or shutting the valve is reduced as we ascend. I'll briefly discuss some of their functions and the important numbers acting on each version. All of these have gone through their paces in the same old marauder, as I've experimented over the last 7 years modding and tinkering. I won't be covering hammerless valves here as they are much more complex and not universally retrofittable to most pcp's like the below variety.
A: Standard poppet @ .276" OD, .125" stem, at 2000 psi with 5lbs of valve spring has 129 lbs of force holding it shut, and 29 lbs of peak closing force on the poppet while opened prior to pressure drop. Required 50 grams of hammer and 7.7 lbs of hammer spring .8" hammer travel. .6 FPE / 2 momentum
B) Standard poppet @ .276" OD, .78" stem, at 2000 psi with 5 lbs of valve spring has 129 lbs of force holding it shut, and 14 lbs of closing force on the poppet while opened prior to pressure drop. This valve required 50 grams of hammer and 6 lbs of hammer spring to operate. .8" hammer travel. Roughly .5 FPE / 1.64 momentum
C) Balanced valve, .295" OD, .125" stem, at 2000 psi with 5 lbs of valve spring, it has a .234" balance piston, which reduces the force holding it shut to around 55 lbs of force, with 29 lbs of closing force while opened. This valve required around 20 grams and 7.7 lbs of hammer spring to operate. .8" hammer travel. Roughly .45 FPE. / 1.2 momentum
D) Balanced valve, .295" OD, .078" stem, at 2000 psi with 5 lbs of valve spring, with the same .234" balanced piston and 55 lbs of force holding it shut, it only has a peak of 14 lbs acting upon it while open. This valve required 15 grams and only 5 lbs of hammer spring to operate. ..8" hammer travel. Roughly .384 FPE. / .902 momentum
E) O-ringless Pilot Valve. .315" OD primary which reduces to .276", and .117" OD Pilot head, .125" stem, at 2000 psi the pilot head only has 24 lbs of force holding it shut with a 2 lb valve spring, while the primary has 159 lbs holding it shut. This valve operates with 4.8 grams of hammer, 4 lbs of hammer spring, .044" hammer travel. Roughly .12-.13 FPE / .277 momentum
As you can see, even a balanced valve taken to an extreme degree of balance with a reduced stem diameter to remove as much closing force as possible while remaining tunable, the reduction in hammer energy needed to operate the valve is reduced a fraction of what a pilot valve can accomplish. These above examples are all quite extreme, taken as far as they can be while still being very functional and tameable via hammer strike.
As you ascend through each poppet variation, the design and fabrication that goes into them gets far more complicated, as well as tuning them and setting them up. They all have their pros and their cons, but the benefit to sharing this knowledge is that nearly all pcp's can be retrofitted with the above valves, depending on your guns or personal limitations, its nice to have options if you want to reduce the required hammer strike needed to operate your valve, which results in a smoother shot cycle with less harmonics disturbing your point of aim and thus point of impact.
As you see above, I favor peek. In case you're reading and aren't familiar with the material selection, it's due being less compressible than many counter-parts, which a hammer strike has to over come, the compression of your poppet against the seat, it also stands up to wear and tear much better with this so you're only extending the life of your poppet going with peek or peek filled varieties.
Both Pilot and balanced valves rely on properly sized vents and chambers with ideal volume which can vastly change how they operate, from requiring a lot of hammer strike, to requiring very little, while the latter generally has an unstable or unreachable low end due to not being able to close the valve fast enough (too much volume/not enough vent), and the former is rather undesirable as the whole purpose of going this direction with valves is to reduce hammer strike while retaining tunability, which is why there is the Goldilocks zone for vent sizing and volume within chambers. Both designs for PV and BV above have adjustable height / chamber volume, and adjustable vent sizing (also known as jets) that help one find their Goldilocks zone.
I could write a lot more in regards to the pros or cons of all the versions, or their inner-workings and what makes them tick, but I'll keep this simple to make it more digestible for now and to not clutter this primary post covering some basics.
-Matt
