Apeks venturi lever and air consumption

[BlueTrin]

i had a go today at turning the Venturi lever. Usually I have it and the effort knob all turned to ‘-‘.

Today I tried turning the lever all the way to ‘+’ and the turned the know a bit: this dramatically increased my air consumption.

I thought that this would only make the regulator easier to breathe but I didn’t think it would have the side effect of increasing my breathing rate ? Is that something I misunderstood?

 

[tbone1004]

you should have the venturi lever and the effort knob both turned to + while diving. The venturi baffle is there to minimize risk of a freeflow, as is the effort knob, when you are not actively breathing that regulator.

If your SAC rate changed, it's because you wanted it to, not because of the regulator. I would recommend using the regulator as it was designed and your SAC rate will balance out eventually.

 

[BlueTrin]

you should have the venturi lever and the effort knob both turned to + while diving. The venturi baffle is there to minimize risk of a freeflow, as is the effort knob, when you are not actively breathing that regulator.

If your SAC rate changed, it's because you wanted it to, not because of the regulator. I would recommend using the regulator as it was designed and your SAC rate will balance out eventually.

I’ll try, the difference was massive though. Maybe like you said it’s something to get used to.

 

[dmaziuk]

I tend to have both my soft palate and glottis open when breathing; most rental regs will "freeflow" into my mouth and out the nose into the mask. I have to consciously exhale a little and/or plug it up with my tongue, it did get annoying enough once or twice that I ended up asking for another reg.

I don't think it affects my SAC that much though.

 

[tbone1004]

I’ll try, the difference was massive though. Maybe like you said it’s something to get used to.

define massive. Are you sure it wasn't inadvertently freeflowing slightly and you didn't notice it?

 

[BlueTrin]

define massive. Are you sure it wasn't inadvertently freeflowing slightly and you didn't notice it?

Ah that could have been it.
Usually with a buddy who has the same air consumption than myself (I usually used 10 bars more than him in a dive) I used 150 bar when he used roughly 100.

Also we were with another group who was kicking and moving around the place all the time and they also used less air than me.

I tried the whole dive to move less as I saw that I was using more air than usual.

How would I have noticed a tiny freeflow ? Would there have been a constant stream of bubbles even not when exhaling ?

 

[tbone1004]

@BlueTrin there could have been. Open the screw all the way and listen for a slight hiss. Many regulator techs will tune the primary second stage to hiss ever so slightly when it's all the way open. You can check this by either listening at the surface, or when you are in/near water next, fully flood the second stage and open the dial all the way and check for any bubbles.

It is also possible that because breathing was near effortless on inhale that your breathing pattern was accelerated. Part of why I like Poseidons is that you have to ask them if it is OK to breathe. They immediately respond with a yes and then force gas down your throat, but you can't "sip" on them like you can with most second stages. This makes you have to consciously initiate an inhale and I find my sac rate is about 10-15% better with a Jetstream as it is on a Scubapro style second stage.

 

[dmaziuk]

How would I have noticed a tiny freeflow ? Would there have been a constant stream of bubbles even not when exhaling ?

It'd have to go somewhere and that's your mouth. You should be able to feel that. You should hear the leaking o-ring behind your head, and freeflowing backup 2nd if it's up on/near your shoulder. Leak form the spg you probably won't hear, but you should see it when checking gas. (With spg, though, leaks may start and stop as you turn it.)

 

[BlueTrin]

@BlueTrin there could have been. Open the screw all the way and listen for a slight hiss. Many regulator techs will tune the primary second stage to hiss ever so slightly when it's all the way open. You can check this by either listening at the surface, or when you are in/near water next, fully flood the second stage and open the dial all the way and check for any bubbles.

It is also possible that because breathing was near effortless on inhale that your breathing pattern was accelerated. Part of why I like Poseidons is that you have to ask them if it is OK to breathe. They immediately respond with a yes and then force gas down your throat, but you can't "sip" on them like you can with most second stages. This makes you have to consciously initiate an inhale and I find my sac rate is about 10-15% better with a Jetstream as it is on a Scubapro style second stage.

I’ll try the turning it all the way at the end of a dive.

It’s interesting to hear that you get 10-15% air (and more diving time) on a Jetstream.

 

[tbone1004]

@BlueTrin it's only because it forces me to think about breathing. If left to my own devices I naturally breathe around a .65-.7. If I pay attention I am comfortable at a .45-.5