D420! How about that?

[scubadada]

I think that WOB on the exhalation arm and bubble interference may be related at times, but are also separate topics. I'd be interested in what others think.

 

[rsingler]

I think that WOB on the exhalation arm and bubble interference may be related at times, but are also separate topics. I'd be interested in what others think.

@couv made a good point about chimneying. It's alluded to in that video back in post #160, around 3:30 minutes. I think there's a way to get width and bubble separation without chimneying (think Atomic M1), but it's probably best in only one position. More vertical sweep to the tee, more chimneying, with the potential to keep the exhaust valve open for a wet breath, as @couv pointed out.
It's exciting that not everything has been invented yet!
When you look at the WOB loop, it's clear that we can still make progress in making our breathing as natural and effortless as possible, and the remaining work is all on the exhalation side, especially if you cheat and reduce cracking effort to below spec (trim the bottom right hand corner of the pic with low cracking effort).

Remember that this curve is at 165' depth, (sometimes in cold water), with an RMV of 2.2 cu ft/min. Navy standards are even tougher.
Cold Water Scuba Regulator Testing — U.S. Navy vs. EN 250
Everything's much easier where most of us dive.
Dunno, maybe the "fuggedaboudit" divers are right. But I still like new toys.

 

[scubadada]

@rsingler makes good points.

The European conformance standard EN250 is performed at 25 breaths per minute at 2.5 liters per breath. This gives a RMV of 62.5 liters per minute or 2.21 cubic feet per minute. This test is performed at 165 fsw/6 atm.

The US Navy Class A test is 25 breaths per minute at 2.5 liters per breath. This gives a RMV of 62.5 liters per minute or 2.21 cubic feet per minute. This test is performed at a depth of 198 fsw/7 atm.

These are 2 of the 4 ANSTI simulator tests performed for the annual ScubaLab regulator reviews. This topic has been discussed previously on SB Latest ScubaLabs reg test - huh?

Think about your own RMV and the usual depth of your dives to put these tests into some perspective.

 

[rsingler]

I'm out scouring the Web for ANSTI loops.
Hard to find. Here's the Poseidon XStream:

 

[rsingler]

Dive Rite 2012

Scubapro Mk25/G260

Scubapro Mk17EVO/G260

Interesting stutter in the G260 between the two tests. Exhalation portion should be independent of the first stage, so that just shows the sort of variability you can get with the "same" regulator. Or maybe the particular ANSTI machine.

 

[rsingler]

And just for reference, a poor one.
This is an unknown regulator used to portray an ANSTI loop in the British
Health and Safety Executive Report 424 from 2006:

Probably a downstream regulator with minimal Venturi assist.

I don't know that all the above loops are under the same conditions, either. So, take with a grain of salt.

 

[scubadada]

And just for reference, a poor one.
This is an unknown regulator used to portray an ANSTI loop in the British
Health and Safety Executive Report 424 from 2006:
View attachment 568681
Probably a downstream regulator with minimal Venturi assist.

I don't know that all the above loops are under the same conditions, either. So, take with a grain of salt.

This one would have failed the ScubaLab testing at these conditions as its inhalation resistance was greater than 25 millibars

 

[buddhasummer]

Did I mention I love how easy it is to tune? The original D was bit of a pain.

Have mine now set with lever about 1/2mm below rim of case, cracking at just over 1". Will dive Sunday and report back.

 

[Father]

As @rhwestfall says, Environmentally Sealed.
Lots of fine grit/trash where I shore dive, that gets stuck in the crack where the piston head meets the land, and slowly chews up the reg head, despite good washout. It's slow, and minor. But I'm finicky about making my best gear last 30 years.
For my old rant on this subject, see
Piston or diaphragm
I'm a piston guy, but when Scubapro stopped SPEC environmental sealing, I went to Atomic for my pistons.
The Mk17 is a fine diaphragm reg (though not as good as the XStream). But neither have a turret. The Mk19 does...

I'm slowly reading through this thread so I might end up replying to more than one comment in close succession as I go. Apologies in advance.

@rsingler (and other non-MK25 fans)... where and how are you diving to get so much grit/trash in the MK25 that the MK19 is so preferable? I know it's not the case as you're all no doubt very seasoned divers, but the visual I get is you diving inverted with your 1st stage dragging through on the bottom through the sand. LOL
I'm not trying to come off as a d*ck or a troll. I'm genuinely wondering. I'm pretty limited in experience in terms of locations. Pretty much exclusively warm Pacific locations with minimal contamination unless I'm inside a wreck.

I was on board for the D420 initially, but the farther I read the more I'm not entirely sure it's something I need over a G260. I dive sidemount more than single tank these days and I rarely invert myself. But I also do a lot of scootering. Rob (can I call you Rob?), you mentioned some concern in I think unboxing video 3 about the D420 freeflowing while scootering. This may have been discussed already and I just haven't gotten far enough into this discussion to see it, but that's definitely a key factor for me.

Also curious if there's any performance differences at 130 fsw and greater compared to the G260.

I'll probably respond more later.

Thanks again for all the great information so far.

 

[buddhasummer]

You certainly don't "need" it over a G260. I dive both and if I had to choose right now I'd choose the G260 no question. But, I'm still hoping it's just because mine was badly tuned out of the box, another member here experienced the same issues as me out of the box but I'll let him post more on that.

Having said that I've never bought a SP reg that has been operating properly out of the box, 8 and counting, seems they have issues correctly tuning second stages out of the factory, perhaps another days "training" is needed.

I'm hoping that my trial and error attempts at tuning it properly will yield sea parting spectacular results. I'll find out tomorrow.

As for piston regs my main reason for not liking them is consecutive bad experiences with them. For me a sealed diaphragm reg is just easier. I don' need to be so careful with post dive rinsing and don't need to worry at all about it "freezing", I dive a wide range of temps. Apeks 1st stages are very simple indeed and can be serviced in a very short time by me on a rocking boat with no specialized tools, save a C scanner if you can call that specialized. Is any of it a big deal? No, personal preference only, they suit my personality better. YMMV. Cheers.