efficiency question plenum size versus pressure

[HYspd]

i think this is the right place to ask...

big plenum at low pressure....or small plenum at high pressure....which would theoretically be more efficient?...

lets says qb78 size tube at 1400psi versus a Fortitide's thumb size valve at 2200psi...both set for say 700fps with a 14.3gr pellet (hope that's an apples to apples comparison)

[rsterne]

Generally, for a given FPE, higher pressure is more efficient.... This is because you can use less dwell.... and use a smaller sip of higher pressure, rather than a longer push from the lower pressure.... That applies regulated or unregulated....

Once you have that as your baseline efficiency, the plenum size, if appropriate for the FPE level, should not matter very much.... If one gun has a plenum of 1 cc per FPE, and the other only 1/4 cc per FPE.... I would bet on the one with the larger plenum being more efficient.... even if the pressure is lower.... Generally, plenum size is more critical on high powered guns, of course.... and less important (or can be more easily compensated for with more pressure) on low powered PCPs....

To your specific example.... 700 fps with 14.3 gr. (15.5 FPE) is pretty low powered for 2200 psi.... so I would bet on that having higher efficiency, even with a small plenum.... because it won't use much air per shot....

Bob

[Bill G]

Yeah, what Bob said. Here, have a GTA cookie and lets ponder for a minute.  If you anticipate wanting to shoot heavier or get into some serious mods, for say shooting cast slugs, Then make sure you have adequate plenum for the future.  So consider what your maximum expected performance might be and build a plenum to suit.  From there you can modulate performance with valve dwell( hammer weight, hammer spring and stroke) and PSI.
I mention this because......Well you are on a forum that lures all into an obsession .

Bill

[HYspd]

Yeah, what Bob said. Here, have a GTA cookie and lets ponder for a minute.  If you anticipate wanting to shoot heavier or get into some serious mods, for say shooting cast slugs, Then make sure you have adequate plenum for the future.  So consider what your maximum expected performance might be and build a plenum to suit.  From there you can modulate performance with valve dwell( hammer weight, hammer spring and stroke) and PSI.
I mention this because......Well you are on a forum that lures all into an obsession .

Bill

I'm not obsessed....only 16 of my 27 airguns are modfified...that's barely half of them!