Poseidon Cyklon regulators

[Billdiver]

If you mean the Xstream 1st stage, the spring being exposed like that results in water flow for heat exchange, which is in fact why it does not freeze.

Good point, now I see it. That picture really shows it too, no ice in the spring chamber even though the rest is covered in a 1/4” of ice.

 

[Billdiver]

Can I buy an Xstream first stage and use it with either a Cyklon or Xstream second stage? Are the new Xstream 1st stages adjustable for the different IP?

 

[Mobulai]

Can I buy an Xstream first stage and use it with either a Cyklon or Xstream second stage? Are the new Xstream 1st stages adjustable for the different IP?

AFAIK (from reading previous posts by bigbella and tbone) that it’s an either or, you can adjust the IP bias spring on the 1st stage to match either the X/Jetstreams (low, around 120psi) or the Cyklons (high, around 170psi)
But you can’t have both 2nd stages on there without one of them giving subpar performance

 

[Bigbella]

The Xstream is now fully adjustable for use with either model of second stage, though as @Mobulai already mentioned, not at the same time, since the Cyklon X is currently set at 11.5 bar (167 psi) and the Jetstream and Xstream seconds, far lower, at 8.5 bar (123 psi) -- a considerable spread.

At one time, though, the Diveair / Cyklon 5000 had been set to 10-10.5 bar; so too, was the Jetstream / Odin. The Oceanair / Thor (an earlier Jetstream), had been set even higher than later Cyklon models, to 12-12.5 bar, though I knew of no one who set the IP that high -- that made for some rough breathing.

Oddly enough, and one of the few missteps Poseidon had ever made (aside from the colors of some of their suits -- oh, what the hell?) with the best first stage that I've ever owned, was to initially release the earliest Xstream, more than twenty years ago now, without any way of adjusting its IP -- no external screw at all, for which I blame an overabundance of aquavit . . .