Remaining Air Time calculation on Suunto Vyper Novo

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Knowing the SAC is the more valuable thing in my view. AI is a nice to have, because it's painless, can see it over a portion of the dive with the right tools (e.g., before & after that shark came by!), and it provides feedback DURING the dive.

However, if you take the time to record pressure a minute or so into the dive (after the initial cooling is over) and at the end, you can get the overall dive SAC easily without AI. It's a cost vs benefit thing that will be a personal call.

+1 on Subsurface. Can enter the start/end pressures manually so it knows your SAC if you don't pony up for AI. Seeing that decrease (it has graphs) as you gain more dives is... satisfying.
 
I think it's great you're looking to plan your air. Along those lines, consider what that 500 PSI reserve is for -- to get your buddy up during an air share. Recall that multiplier for 60 ft ascent was 8 (with safety stop). If buddy's rate is the same as yours but in the stress of the moment doubles and yours doubles, that's 24x the normal rate. (Not 32x since you were already planning on a normal accent without using the reserve.) If your consumption (SAC) is normally 20 psi/min, you'll just barely make it.

If you or they have worse consumption rates or ESPECIALLY if you're deeper, that measly 500 PSI won't cut it.
I think it's great you're looking to plan your air. Along those lines, consider what that 500 PSI reserve is for -- to get your buddy up during an air share. Recall that multiplier for 60 ft ascent was 8 (with safety stop). If buddy's rate is the same as yours but in the stress of the moment doubles and yours doubles, that's 24x the normal rate. (Not 32x since you were already planning on a normal accent without using the reserve.) If your consumption (SAC) is normally 20 psi/min, you'll just barely make it.

If you or they have worse consumption rates or ESPECIALLY if you're deeper, that measly 500 PSI won't cut it.
I w
Thank you so much for the explanation. This is why their calculation of remaining air time based on 500 psi reserve did not make sense to me. I know it also has additional warning alarm set at 700 psi that you can manually increase if required, but obviously for the planning purposes it does not really do any good as you have to figure out these limits manually anyway. I wonder if their DM5 software has any such planning functionality.
I wonder if there is an App for these calculations.
 
I w

I wonder if there is an App for these calculations.
The Subsurface dive planner makes these sort of calculations. A spreadsheet would also be relatively easy to create.
I'm not aware of anything outside of a spreadsheet on a mobile platform, though.

An approximation I use when diving AL80s with insta-buddies is a cylinder pressure (PSI) of 10x our depth in ft.
 
I don't add 500 psi on top of the 10x amount but I have heard that some do. The 10x covers my assumed total SAC rate of 2 cuft/min. One can make a case that rate is insufficient, but that would change the multiplier, not add a constant. I suspect some people are trying to leave 500 psi after an emergency ascent, which doesn't make a lot of sense to me.
 
https://www.shearwater.com/products/swift/

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