Regulator tuning

[rsingler]

My manufacturer writes that I should adjust my D400/350 to 1,4-1,6 inch/h2o.
Well, that's definitely not good enough for me with that 2nd.
I wouldn't dive my Ds with a cracking effort higher than 0,7 inch/h2o and I haven't realized any free flow in any dive position.....

Yes, @axxel57 , but as you know, the D's are unique in having such great case geometry. Almost every other reg (except Poseidon and Hollis 500se) has case geometry that makes the manufacturer spec cracking effort more appropriate.

Yeah, you found one of the few exceptions, but generally, tuning hot carries consequences that most divers neither understand nor can make use of.

You guys are both right.

 

[txgoose]

In regards to the point mentioned by the OP concerning the dive shop owner telling him that he would swallow air and increase his air consumption, I just find it amusing that some folks here took the OP's word at face value and started to tell him to find another dive shop and all of the words that went with that. I don't believe what the OP said concerning this point and I am more inclined to believe that the dive shop owner told him that he would be wasting air thru regulator leaking air and thus influencing his air consumption rate to increase which is very true and is probable should the regulator be tuned to the edge beyond mfg's specs. The dive shop owner was telling the truth, that is all what he told the OP.

A free flowing regulator does way more than double one's consumption. If a dive shop can't explain the difference better than the OP received it, I'd still get a new shop. There is a huge difference between a two to four minute dive and doubling of consumption. And should be fairly easy to detail the differences. I guess we could argue the hypothetical point of a octo that was free flowing, fixing itself, free flowing again and fixing itself, ad nauseum. I'd actually tend to bet that the dive shop person came up with words that sounded plausible to defend their policy to try and not sound like the bad guys. They aren't bad guys if they just state the policy. Gets a bit more sketchy if they make up stories.

 

[Rusty Shackleford]

My manufacturer writes that I should adjust my D400/350 to 1,4-1,6 inch/h2o.
Well, that's definitely not good enough for me with that 2nd.
I wouldn't dive my Ds with a cracking effort higher than 0,7 inch/h2o and I haven't realized any free flow in any dive position.....

Go back and re-read what I wrote. Notice the word CONVENTIONAL. That was included to specifically exclude regulators like Poesidons and the D series.

 

[Daniel M. Thomas]

The dive shop owner is doing and saying what he should be doing and saying, tune the equipment per manufacturer's specs, or within the range specified by the mfg., nothing more and nothing less. I have played around with my regs. where I tuned them to the edge of free flowing and they would appear to be stable on the surface but they will eventually leak air during the dive at different degrees and waste air and, indeed, increase my apparent air consumption rate underwater (I know what my typical SAC/RMV values are and compare them with values for when I am using a regulator tuned to the edge beyond mfg's specs and I know that it was "bubbling" or leaking air during the dive). In short, stick with the manufacturer's specs, go by the book, live by the book, the book is GOOD!

In regards to the point mentioned by the OP concerning the dive shop owner telling him that he would swallow air and increase his air consumption, I just find it amusing that some folks here took the OP's word at face value and started to tell him to find another dive shop and all of the words that went with that. I don't believe what the OP said concerning this point and I am more inclined to believe that the dive shop owner told him that he would be wasting air thru regulator leaking air and thus influencing his air consumption rate to increase which is very true and is probable should the regulator be tuned to the edge beyond mfg's specs. The dive shop owner was telling the truth, that is all what he told the OP.

You may not like to hear it, but you are wrong. I know what i heard thank you. He went as far as telling me americans call regulators "demand valves", and with no breathing resistance there is no demand there.. I'm not sure i agree with that either as it seems they are called regulators on this forum just as they are in the UK.. He seems to think that having a regulator with no breathing resistance increases air consumption, hence telling me not to buy poseidon's because they will do exactly that. I'm not sure i agree with him there and i'm still curious to try poseidon regulators when i get the opportunity.

 

[Bigbella]

I am surprised by the number of folks in this thread that are unaware of the medical fact that if you set a reg close to the edge, it actually increases the diver's tidal volume. This was covered in one of the Marvel movies. I forget which one though. I really don't feel like you guys and gals are paying attention.

PS, OP, get a new shop!

Some manufacturers actually call for the cracking effort to be set, close to that edge; or, within a range -- to the particular tastes of a customer -- and I never really put much credence in the Spam® in-a-can "physics" of Marvel movies . . .

 

[txgoose]

As an aside -- didn't see any films after Ironman -- and Downey would have been Spam® in a can, in that one, just based upon his impacts . . .

I am confident that it was some sort of nanogel that kept his insides from moving at different speeds from his skeletal structure during rapid deceleration. Super powers let a person let go from reality. Ignoring physics for mortals has always seemed a bit odd to me. Can you imagine the autopsy? "How are all of his bones intact but his innards look like a bad jello mold?"

 

[Bigbella]

Say, what ever became of that guy?

 

[cerich]

Yes, @axxel57 , but as you know, the D's are unique in having such great case geometry. Almost every other reg (except Poseidon and Hollis 500se) has case geometry that makes the manufacturer spec cracking effort more appropriate.

Yeah, you found one of the few exceptions, but generally, tuning hot carries consequences that most divers neither understand nor can make use of.

You guys are both right.

actually it isn't the case geometry that makes it so great (and it is a great reg). Some folks in the industry love throwing "case geometry" around while doing technician classes or marketing (which are mostly one and the same) but case geometry is only a part of the story, and none of the story with cracking effort which is what the we are talking about right now, versus WOB which is a much more accurate and complete story.

 

[BoltSnap]

He seems to think that having a regulator with no breathing resistance increases air consumption

If it is leaking air or free flowing, it will indeed increase the consumption rate of the air in the tank, no doubt about it. If "no breathing resistance" means 0 cracking pressure, then it is free flowing and thus it is increasing the consumption rate for certain. This has nothing to do with your first claim about

end up swallowing air rather than breathing

You need to settle on what you THINK you heard and what the person at the dive shop ACTUALLY SAID.

 

[Angelo Farina]

Here two mixed views are contrasting:
1) A reg tuned too close to freeflow is actually freeflowing while diving, hence it wastes a lot of air. This is definitely true, and it is the reason for which I never recommend tuning below 1 inch, and I tune mines around 1.2-1.3
2) A reg tuned very light increases tidal volume, hence the diver breathes more air.
This second point is very questionable. It is true that a percentage of divers do not control their breathing in any way while diving, and hence it can well happen that the uncontrolled breathing is modified by the breathing resistance.
Most divers, indeed, exert some sort of voluntary control on their breathing (or should do, perhaps forgetting under some circumstances), with long expirations emptying almost entirely their lungs (for removing as much CO2 as possible) followed by long inspirations (not reaching the maximum volume, but something as 3/4 of it). This is how I did teach the 1000+students I had, and how most of people I did dive with were trained.
In the case of voluntary respiratory control, having a reg easier to inspire is not changing the way you breath.
But even if it is true that a soft reg increases the tidal volume for divers who have no control on their breathing, that does not mean that SAC will be larger. In effect, the slow, controlled breathing technique described above, despite increasing the vented volume to almost 5 times the normal tidal volume, does not result in any increase of SAC. It can often cause SAC to reduce significantly compared to uncontrolled breathing...
Hence if it is true that a soft reg increases the tidal volume, but simultaneously decreases the number of respiratory cycles per minute, the SAC could actually reduce (and the risk of CO2 retention will also be reduced, as the larger the vented volume compared with the dead space in trachea).