Mares Carbon 42 or Scubapro A700/MK17 for back up reg

[LeadTurn_SD]

i definitely notice the dry mouth with legend compared to the Abyss I owned and the A700 i currently own. What cracking effort do you set your Abyss at and the octo?

Jeff

Hi Jeff,

I tune my Mr22/Abyss to crack at about 1.2 - 1.3". I think if you try to go very much below that cracking effort you'll begin to run into case geomentry fault issues (tendancy to freeflow in certain head-down positions). At 1.2 - 1.3" air delivery is smooth and easy. I dive "warmish" water here in Hawaii, so I set IP to about mid-upper-range of factory spec (about 145 psi).

What I've found is that if you strictly follow the procedure in the repair manual, you'll get stable, "acceptable" performance from the Abyss 2nd stage, but not great performance.... cracking effort can end up about 1.8 - 2.0.

You (or the tech) really need to spend the time and properly "tune" the 2nd stage, paying particular attention to correct lever height. It is a balancing act betrween orifice depth and lever height, and takes me a bit more time to "get right" than tuning a balanced barrel-poppet type 2nd stage. Some techs don't spend the extra time needed to tune the Abyss properly, and you'll end up with "ok" performance, not "great" performance.

Tuning the Abyss is not at all hard, but you do need to spend an extra 5-10 minutes to get it just right. Not just: "Orifice all the way in, then backed-out 3 turns, set lever height using height gauge, test for leaks, make sure cracking effort is within factory specs" and call it a job well done .

I don't really find that I need to detune my Mares octo's. Mares only recommends a few tenths difference in cracking effort between primary and octo anyway. But, you do need to handle any well-tuned reg carefully when it is out or your mouth. If you are sloppy, they will freeflow on the surface. I've found once the 2nd stage is full of water, it is completely fine. I've used Abyss and Voltrex 2nds (same as Abyss) set at 1.3 cracking effort as secondaries and on stages and ponys without any problem.

Best wishes.

 

[hg frogman]

LeadTurn_SD, your post says it all.

 

[Fishpie]

Agreed, the Voltrex/Abyss is one of the "greats".

A few years ago I services one of my personal sets a Voltrex with a MR III back-up.
When putting it all back together I mixed up the cover plates and got the Voltrex cover plate on the MR III body and vice-versa.
I took me 3 months and a good 60 dives to notice my mistake.......and I'm very picky about what I put in my mouth.
And the moral of this hijack.....dunno....the MR II/III is a great reg too?

 

[scubafanatic]

I don't know. The MR22, being bigger, may have a bigger flow, but I am not sure. The MR22 has one bigger hose for the primary second stage (more flow then, but it may be marginal unless at extreme depths) and three other regular hoses, while the MR42 has four regular hoses (that can also be an advantage for routing) if I am not wrong.

I prefer the Abyss than the Carbon (price, plus brass seems more resilient to me ; also weight in the water is a non-issue : no problem with the Abyss, provided one changes the original floppy Mares mouthpiece).

But frankly, given that you already have a Mk25/A700, why not buy another Mk25/A700 in order to standardize your equipment (spare reg, spare parts etc). From what I have read that was written by competent divers, it's an excellent reg. And it offers more routing options than the Mares for diving a twinset or an H-valve as you seem to do.

...about the larger diameter primary 2nd-stage hose, I actually got rid of that larger diameter hose years ago when I switched my RUBY to an Atomic swivel hose (Atomic uses the standard diameter hoses) and I had to install a small 1st-stage LP port converter so that the smaller diameter Atomic hose would screw into the larger diameter RUBY 1st-stage port, and I can't say I ever noticed any difference in airflow, I suspect I'd have to be way beyond recreational depths before I could possibly notice any differences in airflow, and anyway, my other high-performance regs (Atomic/Apeks/Poseidon) all use standard diameter (smaller) LP hoses on ALL their LP ports, so those manufacturers don't seem to feel the larger diameter LP hose to be needed in the first place.

 

[LeadTurn_SD]

...about the larger diameter primary 2nd-stage hose, I actually got rid of that larger diameter hose years ago when I switched my RUBY to an Atomic swivel hose (Atomic uses the standard diameter hoses) and I had to install a small 1st-stage LP port converter so that the smaller diameter Atomic hose would screw into the larger diameter RUBY 1st-stage port, and I can't say I ever noticed any difference in airflow, I suspect I'd have to be way beyond recreational depths before I could possibly notice any differences in airflow, and anyway, my other high-performance regs (Atomic/Apeks/Poseidon) all use standard diameter (smaller) LP hoses on ALL their LP ports, so those manufacturers don't seem to feel the larger diameter LP hose to be needed in the first place.

I think you are probably right. I use an adapter so I can use standard hoses on the DFC port of my MR22. I think Mares may be the last manufaturer still making a 1/2" primary port (but I think it is only on the MR22 now???). I think in theory the extra volume a 1/2" hose provides could help offset increased density of air at depth.... the reality may be that there was not that big a difference, and that most dives at great enough depths to warrant the increased diameter are conducted using Helium in the breathing mix, with is lower density than air, so the theoretical advantage of the 1/2" hose would be unnecessary?

Subjectively, I cannot tell a bit of difference in breathing resistance at recreational depths between the Mares 1/2" hose and a standard hose...

Best wishes.