DiversL
Registered
For people that own both atomic and SP, does the Atomic AFC really breathe better than the scubapro’s venturi switch? Let’s say T3 vs S620?
AFC OR venturi switch?
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The Atomic AFC does breathe better and is worth it. It doesn't matter what Atomic second stage, they all perform the same when tuned to factory specs. The AFC adjustment is based on depth and max's out at around 20 meters (full effect). It is more convenient than having a switch to turn the venturi on in my experience.
Brian G
Contributor
Both the T3 second stage and the S620 work extremely well. The AFC on the Atomic is automatic vs the S620 manual operation. For those who forget to make adjustments to their regulator while diving, the AFC will probably lead to the best experience. For those who like full control, the S620's manual adjustment will likely be more satisfying.
This is actually a very interesting question. Diving both SP and Atomic, I'd have to say that the technology advance favors Atomic. Why?
New SP regs are designed to be dived with the Dive switch in the Dive position (Duh). That is, full open (with the octo perhaps left in Pre-Dive throughout). That wasn't always the case. When we were taught to tune the G250 (that did not have a "handle" on the venturi adjustment), we were taught to tune the vane so that it would spontaneously stop freeflowing after a second or so. Full open would yield nonstop freeflow with a bang on the purge button (as it should), and of course full "closed" (pre-dive setting) would not freeflow at all, as increased turbulence inside the case from the vane position prevented negative pressure from developing.
In the current SP regs, the only adjustment in the manual other than full on/full off is the positioning of the vane itself (done by the tech). With the cutout in the vane facing toward the mouthpiece (what SP calls the "rental" configuration), the reg still will not freeflow, but will generate slightly better flow in the dive position than in Pre-Dive. In the opposite configuration, the reg will freeflow with a brisk tap on the purge button in the Dive position.
What's the point? At significant depth (>80 ft), air density has a greater effect on airflow. The larger number of molecules passing through the case creates a greater vacuum with the venturi in Dive position, helping overcome greater air density and keeping the valve open. Whether or not it actually shifts over to positive pressure during a breath is known only to the ANSTI machine. I haven't been deep enough with an S600 and sucked hard to see if I could trigger crossover. But the point of the G250 procedure was to "tune" the vane to be just short of freeflow, in preparation for greater air densities. That's no longer needed with the new shape of the S600 vane with its cutout, and it's redesigned case.
With Atomic, and a retractable vane, they've attempted to get the best of both worlds. At the surface, with the vane full out and the Atomic mouthpiece in place, the reg may just freeflow with a brisk tap on the purge, but usually not. Without the mouthpiece and its slight orifice restriction, the reg will of course freeflow, as it should. But at depth, the Atomic vane retracts halfway, decreasing turbulence and allowing greater flow. This preserves flow characteristics as air density increases.
IMO, the breathing characteristics when comparing the two brands depend far more upon individual second stage tuning. If you set cracking effort the same for both regs, I doubt I could tell the difference at the surface. I love the flow of my T2x and T3 at depth (same reg, really), but haven't done a direct comparison with the S600 series.
Rather than Venturi differences, Atomic's advantage to me lies in its seat-saving orifice, and the composition of the LP seat, which resists imprinting and detuning one year into a service interval. Others really dislike that the valve is open when unpressurized. IMO, you just have to be aware of the feature, when soaking your regs.
Performance-wise, it's very close. Consistency between services clearly favors the Atomic, IMO.
My 2 cents.
New SP regs are designed to be dived with the Dive switch in the Dive position (Duh). That is, full open (with the octo perhaps left in Pre-Dive throughout). That wasn't always the case. When we were taught to tune the G250 (that did not have a "handle" on the venturi adjustment), we were taught to tune the vane so that it would spontaneously stop freeflowing after a second or so. Full open would yield nonstop freeflow with a bang on the purge button (as it should), and of course full "closed" (pre-dive setting) would not freeflow at all, as increased turbulence inside the case from the vane position prevented negative pressure from developing.
In the current SP regs, the only adjustment in the manual other than full on/full off is the positioning of the vane itself (done by the tech). With the cutout in the vane facing toward the mouthpiece (what SP calls the "rental" configuration), the reg still will not freeflow, but will generate slightly better flow in the dive position than in Pre-Dive. In the opposite configuration, the reg will freeflow with a brisk tap on the purge button in the Dive position.
What's the point? At significant depth (>80 ft), air density has a greater effect on airflow. The larger number of molecules passing through the case creates a greater vacuum with the venturi in Dive position, helping overcome greater air density and keeping the valve open. Whether or not it actually shifts over to positive pressure during a breath is known only to the ANSTI machine. I haven't been deep enough with an S600 and sucked hard to see if I could trigger crossover. But the point of the G250 procedure was to "tune" the vane to be just short of freeflow, in preparation for greater air densities. That's no longer needed with the new shape of the S600 vane with its cutout, and it's redesigned case.
With Atomic, and a retractable vane, they've attempted to get the best of both worlds. At the surface, with the vane full out and the Atomic mouthpiece in place, the reg may just freeflow with a brisk tap on the purge, but usually not. Without the mouthpiece and its slight orifice restriction, the reg will of course freeflow, as it should. But at depth, the Atomic vane retracts halfway, decreasing turbulence and allowing greater flow. This preserves flow characteristics as air density increases.
IMO, the breathing characteristics when comparing the two brands depend far more upon individual second stage tuning. If you set cracking effort the same for both regs, I doubt I could tell the difference at the surface. I love the flow of my T2x and T3 at depth (same reg, really), but haven't done a direct comparison with the S600 series.
Rather than Venturi differences, Atomic's advantage to me lies in its seat-saving orifice, and the composition of the LP seat, which resists imprinting and detuning one year into a service interval. Others really dislike that the valve is open when unpressurized. IMO, you just have to be aware of the feature, when soaking your regs.
Performance-wise, it's very close. Consistency between services clearly favors the Atomic, IMO.
My 2 cents.
OP
DiversL
Registered
Hello! Wait, what would be the difference when soaking the atomic regs? How should it be done? Performance wise very close but. Slight edge to?
OP
DiversL
Registered
so the AFC maxes out at 60ft... not sure is this is good or bad, let’s say if you decide to 170ft or even tech depths
Just like with clearing your ears, the biggest changes are in the first thirty feet. I imagine Atomic has engineered this with a range of depths in mind. And remember that if you're thinking tec, you're thinking helium, where gas densities are configured to be like that at shallower air depth.
With a seat saver valve, the valve is slightly open when the reg set is unpressurized. When you soak a reg set, it's best to keep the first stage above the seconds in case any water rises up into the hose from the second, and then drain them the same way. A coat hanger works fine, or set the first stage on the counter while you soak the second overnight on the sink.
Though the likelihood is low if you plug the intake of the first stage, keeping the seconds lower prevents a first stage flood. Even that doesn't mandate a teardown if it's a fresh water minor flood. Just connect a tank and disconnect the second stages and SPG, and let intermediate pressure dry things out (hang in to the hose ends!). Then connect the second stages and unscrew the HP port plugs and dry out the HP side through the pinholes.
End of thread derailment. Sorry!
OP
DiversL
Registered
Thanks for all the amazing input!
Divectionist
Contributor
Just watched a video on this AFC thing. This makes me wonder, does anyone actually fiddle much with these settings mid-dive in the first place?
I just keep it on 'Dive' and the breathing effort screw all the way out (S620Ti) on a normal dive, where I enter and exit the water with reg in mouth, boat or shore.
Further, the only two instances where I would switch the venturi off is when bobbing on the surface and clipping the 2nd off to the chest D ring for a while. Venturi stays off on the octo, which is connected to a pony that has gas turned on and it never dared to free flow on me.
When I swap from primary to pony reg (so far just for practice), I do shut the venturi off on the primary to prevent diving in a jacuzzi - I assume there is a switch on the AFC regs to force it to the 'automatic surface setting'?
As far as breathing effort goes, for which some SP regs have a dial, I have not encountered any situation where I had to increase the breathing effort, even swimming against strong flows. So the only use I have for the breathing effort screw is to tighten it for rinsing, then opening it again for storage and diving. Likewise, never have I wished for more airflow, and the WOB on a top of the line SP is significantly lower than on an entry level SP set. I would like to do a direct comparison with the AFC at depth because I can barely believe that there is much left to wish for as far as breathing comfort goes.
I just keep it on 'Dive' and the breathing effort screw all the way out (S620Ti) on a normal dive, where I enter and exit the water with reg in mouth, boat or shore.
Further, the only two instances where I would switch the venturi off is when bobbing on the surface and clipping the 2nd off to the chest D ring for a while. Venturi stays off on the octo, which is connected to a pony that has gas turned on and it never dared to free flow on me.
When I swap from primary to pony reg (so far just for practice), I do shut the venturi off on the primary to prevent diving in a jacuzzi - I assume there is a switch on the AFC regs to force it to the 'automatic surface setting'?
As far as breathing effort goes, for which some SP regs have a dial, I have not encountered any situation where I had to increase the breathing effort, even swimming against strong flows. So the only use I have for the breathing effort screw is to tighten it for rinsing, then opening it again for storage and diving. Likewise, never have I wished for more airflow, and the WOB on a top of the line SP is significantly lower than on an entry level SP set. I would like to do a direct comparison with the AFC at depth because I can barely believe that there is much left to wish for as far as breathing comfort goes.
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