Local Pawn Shop find: double Xstreams

[growcurlyhair]

Having a servo does not imply harder breathing.
As with all things scuba, it comes down to tuning. An Xstream tuned to 1.1" at an IP of 109-123 is sweet. It's the onset of the breath that is slightly more "square wave" than with a lever design. A lever valve goes from "barely cracked" to full flow based on how hard you suck, with at some point Venturi kicking in and maintaining flow at less effort until you exhale and shut the valve off.
In contrast, a servo design is like a trigger. The transition from servo valve opening to main valve opening is very short, and having a high IP makes the sensation almost uncomfortable, simply because the Poseidon outflow is so large. It works, but you don't need that much gas.
The other problem is vocabulary. The Poseidon service manual says "cracking effort". But it's not! It's dynamic inhalation resistance. It's supposed to be 1.1" during a very light inhalation. If you tune it so the servo doesn't crack until 1.1", main valve opening won't be until 1.4"+.
Make sure your tech tunes it so the effort is 1.1" during a tiny breath, and not when the servo cracks open.

Thanks for the mega post. That helps a lot and i will be passing these details forward.

I think the freeflow reg set might have been caused by the hard-press of the purge button like you suggested, likely permanently bent the servo. I will be gentle going forward after its replaced.

I read that its supposed be insanely low WoB with proper tuning, which sounds like a dream; hopefully after a service. It was almost exhausting to use the non-freeflowing set previously on that one dive.

 

[grantmac]

Worth checking the IP, they are rather sensitive to it in terms of WOB.