Balanced Diaphragm Reg Performance - Is This Typical?

[ams511]

At depth the regulator is pushing denser air so it may be a bit harder to breath. As he comes up the air is less dense and the it could feel that the reg is breathing better. This effect could be amplified as his head clears from the narcosis.

 

[Diver0001]

As I ascend during the second half of my dive, my second stage breathes more easily as soon as I reach 10m. It has gotten to the point where I can tell that I have reached this depth without looking at my computer.

I've never dived with the reg you have but it seems very odd to me.

I have noticed with some regs (notably, some unbalanced regs) that the deeper you go, the worse they perform, but the change has always been gradual, not sudden. Being balanced or unbalanced doesn't seem to be the biggest issue. Some unbalanced regs (like the Aqualung Aquarius I have from 1972?) performs better at 40-50 metres than the balanced Sherwood Maxiumus I had from ca. 1990.

My current main is an Aqualung legend and from time to time I literally have to remind myself that I'm under water. That's how well it breathes.

I can't think of any reason why 10m would be significant to how a reg performs. The IP in the 1st stage should be between 8 and 10 bar and if it's balanced then it will be stable throughout any depth range and tank pressure (unless empty, of course). That Mares 2nd stage is a tried-and-true unbalanced downstream design and for the life of me I can't think of a single thing at any depth that would cause it to suddenly perform better/worse than at other depth.

Ergo, if what you are experiencing is real and measurable then there is something wrong with it... although I can't imaging what. Normally, Mares regs are outstanding and reliable so the first thing I would do is get it serviced/inspected.

R..

 

[Aqua-Andy]

Ergo, if what you are experiencing is real and measurable then there is something wrong with it... although I can't imaging what. Normally, Mares regs are outstanding and reliable so the first thing I would do is get it serviced/inspected.

R..

This is great advice, but... I would be willing to wager a bet that the majority of dive shop reg techs out there would have no Idea what to look for and just throw a parts kits at it.

 

[Locus]

However, I'm curious: what was your starting pressure on the surface, and did you happen to look at your tank pressure again when you ascended to your 10m depth?

On the last dive I noticed the breathing change, I started with 3400psi and finished with 2000 after about 45 minutes (most of the dive was shallow).

At depth the regulator is pushing denser air so it may be a bit harder to breath. As he comes up the air is less dense and the it could feel that the reg is breathing better. This effect could be amplified as his head clears from the narcosis.

I'm hoping this is all that it is, and that my being relatively new to this equipment is making me suspect a problem where there isn't one. Until recently I've been focusing a lot more attention on monitoring buoyancy, etc while diving, and it could be that now that I'm progressively doing more of that stuff automatically I'm just now having the free attention to notice these smaller things. In any case, I'll mention it to my LDS guy and see if he thinks it's a mechanical issue.

Thanks for the excellent feedback everybody.

 

[Locus]

Forgot to wrap this thread up.

I had my regs looked at and they replaced the high pressure seat. I no longer notice a difference in breathing ease when my depth changes.

 

[halocline]

Forgot to wrap this thread up.

I had my regs looked at and they replaced the high pressure seat. I no longer notice a difference in breathing ease when my depth changes.

That means that your IP was likely creeping over the course of the dive, the depth change probably had nothing to do with it, just dive time. Replacing the HP seat has no affect on the depth compensation of the regulator.

 

[ams511]

That means that your IP was likely creeping over the course of the dive, the depth change probably had nothing to do with it, just dive time. Replacing the HP seat has no affect on the depth compensation of the regulator.

Leadturn pointed out in one of his previous posts that the OP is using an unbalanced second stage, so IP creep would result in easier breathing as the tank emptied. I am wondering if the regulator was assembled incorrectly before and the dis-assembly required to replace the seat fixed the problem.

 

[axxel57]

It's not unusual at all that MARES 1sts show a 2 - 6 PSI higher IP at 600PSI tank pressure than at full tank. For an unbalanced 2nd this translates in a 0,1 - 0,2 lower cracking effort.

Surprising is only that a beginner can feel the difference.

I can only imagine that the regulator was adjusted pretty lousy (hard),so one could feel the difference. The OP mentioned that he got the air he needed, but that would be probably true also with a cracking effort of 2,6 inch/h2o.

Most 2nds which come from the factory, are adjusted at 1,4 - 1,5 inch/h2o, which is within the manufacturers specifications, but still far from what they can offer concerning the cracking effort.

I would not know what the change of the HP seat could have to do with the mentioned experience, I would guess they also readjusted the 2nds.

 

[rjk75]

Locus,

Don't wrap this up yet.

Forgot to wrap this thread up.

I had my regs looked at and they replaced the high pressure seat. I no longer notice a difference in breathing ease when my depth changes.

Did you get the old parts back or at least get a look at them to see what they were like?

I'm curious because I have two MR42T/Abyss regs and one of them might need a Poppet Seat replacement.

I'm presuming that they would've replaced either one or both of these two items in the first stage.

 

[ams511]

I'm presuming that they would've replaced either one or both of these two items in the first stage.

What is called the poppet seat is more commonly called an orifice or hard seat. These usually only get replaced when damaged or dull. What is called the poppet is more commonly called the soft seat. These usually get replaced during a service but I think Mares doesn't include the soft seat in the service kit. Only orings and a filter. You can purchase them here: Mares Service Kits

This may be helpful: http://www.scubaboard.com/forums/re...y-regulator-maintenance-discussion-mares.html