Both Momentum and Energy increase if you increase the Average Spring Force or Hammer Travel.... However, changing the Hammer Weight changes the Momentum but NOT the Energy.... In terms of increasing valve dwell, all three changes increase dwell.... Increasing the dwell also increases the lift (unless it is artifically limited by the hammer hitting a bumper or buffer).... However, once the lift is greater than 1/4 the valve throat diameter, the flow RATE no longer increases, only the dwell.... Longer dwell releases more air at any given pressure....

I happen to believe that Momentum is more important than Energy in opening the valve because Energy can change forms (to heat and sound) but Momentum can't.... I have graphed both Hammer Energy and Momentum against the valve closing force they can overcome, and the Momentum shows a more linear (and consistent) relationship.... Other than a very small amount of "buzz" (rapid and inconsequential vibration) in the valve stem on initial contact with the hammer, once the hammer hits the valve they move as a combined pair through the entire valve travel until the valve returns to the seat.... At that point, the hammer (it's momentum reversed from the valve closing force) leaves contact with the stem and bounces against (or off of) the spring.... It may or may not reopen the valve.... We don't want it to, because any air released from a second valve opening is totally wasted.... the pellet has long since left the building....

I am of the opinion that without the interaction of the hammer with a third element (a bumper or buffer), a given momentum will open the valve a given amount (lift and dwell) against a given pressure.... I think it matters little if that momentum is achieved through the mass of the hammer, it's travel, or the spring force.... It is the effect of those three elements on the Momentum that governs what the valve does.... Having said that, IF the valve opens faster but less (eg. a light hammer moving fast) it may provide a slightly greater push in the first part of the pulse and yet a smaller total pulse.... That should increase the efficiency.... I think that's where the idea of the bumper/buffer comes in to limit the total lift.... but as yet haven't found the key....

Bob