Question Cracking Pressure Scubapro g260 and Atomic Z2

[Simpel]

I have changed the regulators frequently during the last few dives
the g260 opens at a lower response pressure (according to the measurement)
however, the z2 feels easier to breathe under water
why is that?

 

[Nemrod]

I have changed the regulators frequently during the last few dives
the g260 opens at a lower response pressure (according to the measurement)
however, the z2 feels easier to breathe under water
why is that?

The Atomic is a fine piece of equipment. iI may well slightly perform better. My experience is that you have two very nice pieces of equipment and I doubt there is much difference. I am, skeptical of the settings you posted as well. I just am, I am skeptical of most things, born that way, especially scuba shop "techs" in general.

I would probably take the G260 and recheck the cracking effort. The .8 is below factory specs of 1.0 to 1.2 per the SM. However, I generally set my (primary) G260 second stages to leak very, very slightly with the knob fully out such that I must turn the knob in a half turn to a full turn to stop the tiny leak. For a secondary I would follow the SM.

The Atomic has a very effectivue Venturi. The three aspects of breathing performance are:

1. Cracking effort to initiate flow
2. Venturi to sustain demand flow
3. Exhaust effort

Make sure the Venturi vane on the G260 is set to dive condition.

 

[rsingler]

I have changed the regulators frequently during the last few dives
the g260 opens at a lower response pressure (according to the measurement)
however, the z2 feels easier to breathe under water
why is that?

Cracking effort is only the starting resistance to opening the valve. Internal flow dynamics (including Venturi) determine the rest. Some aspects are exceedingly difficult to measure on the surface, as we can only substitute very high gas flows (number of molecules) for high gas density at depth (number of molecules).

Using an ANSTI machine allows one to get a peek at dynamic resistance at depth, but it is typically only used for certification under conditions that bear almost no relevance to deep recreational diving.

I have been unable to interest anyone in making ANSTI tests at depths and flow rates that approximate a divers effort at max recreational depth under moderate to heavy effort. It might quantify the very observation you have just made, which would then ignite a firestorm amongst the manufacturers. In addition to designing to meet EN250a's unusual requirements (perhaps to reduce liability), they'd now actually have to give us a reg that has smooth characteristics under real world conditions. I think there would be a lot of manufacturer opposition to such comparative data.

It's better for them to have guys like us argue about which toy is best.