Question Good second stage for use as octo

[jellycatsdad]

For a sturdy reg that will breathe well when you need it, that doesn't have the finesse of the D400, but does have adjustable cracking effort and Venturi controls to detune for giant stride, I don't think there's a better value than the Deep6 Excursion (US$120). The case can take a beating, hanging off your bcd. It tunes very light. Service kits are sold to the end user and are very inexpensive.
Otherwise, I'd concur with the S270, or better, the C370, albeit for more $$.

I’m in kinda of a same dilemma with my setup, I’m using Mares but want to chuck my MV Octopus for a full-sized reg. I was looking at a D6 Signature as one of the options. Will it play nice with the higher IP Mares uses?

 

[rsingler]

Sure. It'll tune fine at the higher IP.

 

[rsingler]

I was looking at a D6 Signature as one of the options. Will it play nice with the higher IP Mares uses?

Let me put one on the bench and test it.
More to follow.

 

[rsingler]

So...
A Signature tuned to 1.1" at 130 psi IP will crack at 0.85-0.9" at an IP of 150 (2psi above Mares max spec).
That's too low to avoid slight freeflow in the direct face down position.
If you turn the adjustment knob between 1/3 and 1/2 turn, you get your 1.1" back (though you lose 1/3 of a turn's worth of excursion if you want to raise cracking effort for a surf entry. That's what I'd do. You are merely adding counterforce to oppose the tendency of the higher IP to open the valve.
Alternatively, you could add that last "5 minutes" (1/12 turn) of clockwise orifice adjustment, and that gets you to 1.05", but I hear the faintest of lever clack when I do that, so you've lost a hair of lever excursion.
Either method is safe.

Just for grins, I tried adding the spring shim that we do for springs that get a little tired over the years,

but that raised min cracking effort to 1.4", so it was too much.

Anyway, easy safe fix for pairing it with a Mares at 148 IP.

 

[Mobulai]

Very handy to know how to hack a reg combo, thanks for that @rsingler

Question about this part:

Just for grins, I tried adding the spring shim that we do for springs that get a little tired over the years,
View attachment 884694
but that raised min cracking effort to 1.4", so it was too much.

Anyway, easy safe fix for pairing it with a Mares at 148 IP.

can we theoretically add a shim and then back the orifice out (kinda like a reverse micro adjustment)? Any risk there?

Also what size are these shims? Would be great to keep a few handy

 

[Scuba Lawyer]

I know I'm a dinosaur, but I've used an old Titan II for years when I need to put an octopus on or use a pony. Rock solid construction, very easy breathing and fairly compact. My 2 psi.

 

[rsingler]

can we theoretically add a shim and then back the orifice out (kinda like a reverse micro adjustment)? Any risk there?

No, you cannot back out the orifice in exchange.
Recall that that seal is made first against some nominal spring counterforce, and in a well-designed regulator, the poppet and foot of the lever is smack up against the back side of the square lever broach in the barrel. So adding all the spring force in the world won't move the poppet, since it's mechanically limited.
In the real world, however, some tiny poppet movement and lever drop is common, and may in fact be required by a shallow case, to drop the lever enough to fit under the faceplate (think G250). In those cases, yes - if you increase the spring counterforce, you bury the knife edge just a hair more into the LP seat, in which case you may be able to back off the orifice to the original standard: "sealed plus 5 minutes on the clock".

The spring shim, which works with many reg brands, is very similar to the part actually used by Scubapro as 11.500.029 in the G500 for a similar purpose: getting more spring compression out of old parts used in a new design.
It is McMaster-Carr 95630A217 60 cents each, plus $10 shipping.

 

[jellycatsdad]

So...
A Signature tuned to 1.1" at 130 psi IP will crack at 0.85-0.9" at an IP of 150 (2psi above Mares max spec).
That's too low to avoid slight freeflow in the direct face down position.
If you turn the adjustment knob between 1/3 and 1/2 turn, you get your 1.1" back (though you lose 1/3 of a turn's worth of excursion if you want to raise cracking effort for a surf entry. That's what I'd do. You are merely adding counterforce to oppose the tendency of the higher IP to open the valve.
Alternatively, you could add that last "5 minutes" (1/12 turn) of clockwise orifice adjustment, and that gets you to 1.05", but I hear the faintest of lever clack when I do that, so you've lost a hair of lever excursion.
Either method is safe.

Just for grins, I tried adding the spring shim that we do for springs that get a little tired over the years,
View attachment 884694
but that raised min cracking effort to 1.4", so it was too much.

Anyway, easy safe fix for pairing it with a Mares at 148 IP.

And if I wanted a Mares option for no muss-no fuss option?

 

[rsingler]

And if I wanted a Mares option for no muss-no fuss option?

Dual Adjustable or the XR/HR, tho' @lowwall might know better than I.
Those are the closest balanced designs similar internally to the Signature, except like most Mares seconds, they use the VAD tube on the side to deliver gas, which makes them pretty freeze resistant. They're designed for 148 psi right out of the box.