Ease of breathing adjustment

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

My primary second stage free flows at full open with Venturi assist on - in the water near the surface. It won't free flow in air. And it won't free flow at depth.
 
I think "free flow" is not the correct words here to describe the orifice/seat adjustment being discussed. I adjust my second stages to leak, barely, they are not free flowing. Most regulators, per the SM, must free flow with the Venturi at maximum when initiated by purging. What we are talking about is a leak, the seat/orifice is not fully sealing when the knob is fully out.

The instructions below require a Venturi free flow in the DIVE or Max position (example G250V):



When a second stage is set to barely leak, not free flow, with the knob fully out, it essentially has 0 inches of cracking effort. As has been described, most regs have a case fault geometry that is roughly equal to 1.0 to 1.2 inches between the center of main diaphragm and the top of the exhaust valve in a normal swimming position. With the seat/orifice adjusted as I am describing, and several others, the regulator will leak annoyingly until the knob is turned in approximately 1/2 turn. It will also be prone to free flow in use if the knob is not turned in. That is what is called a hot tune. I would never set a customers regulator that way, but for me and my wife and most of my buddies, a hot tune is the norm.
 
Perfect document, will help me a lot.
Is it necessary to do this adjustment with a full tank ?
 
Perfect document, will help me a lot.
Is it necessary to do this adjustment with a full tank ?
If you are using a balanced first stage it should not matter, the difference in IP will be minimal from full to empty. If you dive an unbalanced first stage as I am known to do as of recent :) then yes, it can matter and the IP from full to empty should be taken into account.
 
All understood, big thanks. Aiming for a hot tune : when adjusting my regs until I get this gentle leak sound, the flow knob is fully open ; what about the venturi knob : all open too or is it irrelevant ?
 
All understood, big thanks. Aiming for a hot tune : when adjusting my regs until I get this gentle leak sound, the flow knob is fully open ; what about the venturi knob : all open too or is it irrelevant ?
The Venturi is not relevant to setting the orifice/poppet adjustments for a hot tune (or any tuning) as I am describing.
 
https://www.shearwater.com/products/swift/

Back
Top Bottom