halocline
Contributor
That's an interesting observation, and since I am not very familiar with the A700, I'm not in a position to doubt you. However, the venturi assist on the G250 is completely different than on the D series, (the D series has no VIVA vane) so I'm not sure how you could put them together in terms of venturi. With the internal baffle off, I would agree that the D series will flow mightily once started, but IME for whatever reason this does not translate to the sensation of having air pushed into your mouth when used in diving. Mostly, though, my post was referring to the dry mouth effect that the OP was concerned about, and how the lack of a VIVA vane in the original metal case SP 2nd stage, combined with the full metal body, would probably be more effective in terms of warming and slowing the air than a more modern, smaller barrel poppet 2nd stage with a metal air barrel.
I've certainly read about the relative stability of the D series vs the older coaxial valve (converted pilot and Air 1) and I understand that theoretically the older ones could be set lower due to even less case fault geometry, because the diaphragm functions as the exhaust valve, as opposed to a center-mount exhaust valve in the D series. But my experience with regularly diving pilots, Air 1s, and D300s is that practically they're about the same in terms of stability. I've had a couple of pilots (again, converted) that I could set very lightly, but had a few free flows in use. At least with the regs I have (six or so D300s, 3 Air 1s, a few pilots) I find more variance in the stable cracking pressure between individual regs than between the models themselves. I suspect small imperfections in the orifices and/or variance in the springs are responsible for that.
---------- Post added April 26th, 2012 at 07:48 AM ----------
With all due respect to your friend, she's giving you very bad advice in this regard. "Top-of-the-line" has ZERO to do with diver safety, although many sales people in this industry love to imply otherwise. It a pet peeve of mine, using fear to sell dive gear.
Top of the line regulators offer somewhat improved performance (meaning easier breathing, not more reliability) and a lot of self-congratulatory hype. If safety is paramount to you and you feel that your regulator choice is important in that regard, get a SP MK2 with an unbalanced downstream 2nd stage like the R190. There's only one moving part in the 1st stage, no dynamic o-rings subjected to HP air, and the unbalanced combination of stages will result in noticeably stiffer breathing at tank pressures below 500 PSI. That way if your SPG fails mid-dive or you forget to look at it, you'll get a reminder that you're getting low on air. But they don't tell you that at the dive shop....I wonder if it has anything to do with the fact that a dealer makes twice as much on a MK25 sale....nah, couldn't be.
Any decent regulator in good working shape will offer about the same level of reliability....they're ALL very reliable. Much more importantly, you need to dive in such a way that regulator failure is an inconvenience, not a danger. Diver behavior is what determines safety, NOT the level of gear purchase.
