Poseidon - xtream vs Jetstream

[iointerrupt]

I've dove my Xstreams hooked up to Mk11s. Works fine. In a lot of ways, the Mk11 is basically a cost-reduced, miniature version of the Xstream first stage.

If you have an IP gauge, real simple to connect it on the Mk11 and use an allen-wrench to adjust it down to 130psi. Then tune the Xstream as you see fit (loosen the lock screw, thread the servo valve in or out).

And yeh, either bring the C370 or an OPV along for the ride.

 

[p_kos]

 Wo

Can you add a xtream to a scubapro mk11 c370 as a octo or vice versa xtream as a primary and 370 as a octo knowing that ip on xtream is 123 and c370 is 130 to 140 would that be a problem. Some like Cave Adventures Ed Sorenson in fl say it's fine you'll never notice and others say posideon has to mate together 1st and 2nd stage. As for pressure relief I've been told that c370 will act as one or if your really concerned add a pressure relief valve to a LP port. It's only the cyklon where IP is 160 that will have a problem. Does any of this make sense just want to add a xtream to a mk11 c370.

As long as you can adjust IP to 123 and have a way to vent overpressure (OPV or extra downstream second stage) any 1st stage can be used.

 

[tbone1004]

 Wo

Can you add a xtream to a scubapro mk11 c370 as a octo or vice versa xtream as a primary and 370 as a octo knowing that ip on xtream is 123 and c370 is 130 to 140 would that be a problem. Some like Cave Adventures Ed Sorenson in fl say it's fine you'll never notice and others say posideon has to mate together 1st and 2nd stage. As for pressure relief I've been told that c370 will act as one or if your really concerned add a pressure relief valve to a LP port. It's only the cyklon where IP is 160 that will have a problem. Does any of this make sense just want to add a xtream to a mk11 c370.

As said above, any first stage can be used provided it has a downstream valve attached to it *either the old style hoses from Poseidon or a dedicated OPV if using 2x Jetstream/Xstream second stages, though your C370 as an octopus will provide that function*, and the IP is tuned to 123.
The C370 is a balanced valve design so it will not really care if you are only giving it 123psi. It will have a slightly higher breathing resistance but it is not going to be really noticeable. I would strongly recommend retuning the second stage once the 1st has been dialed in.
The Poseidon Xstream/Jetstream are UNbalanced second stages which means they MUST be tuned to their specific first stage because their work of breathing is highly affected by the intermediate pressure. To that note, it is also critical that the regulator is adjusted when the MK11 is at its lowest IP. I do not know that first stage well so can't comment if it is going to be at lowest tank pressure or highest, but with the Poseidon first stages it is absolutely critical that you tune the second stages at the highest tank pressure the first stage will see. The Poseidon 3960 and prior are not terribly well balanced and there is a good bit of IP difference between a 4000psi tank and a 400psi tank. If you tune to 123psi at say 3000psi and get the second stages adjusted to that and hook it up to a 3500psi HP tank, they will not have enough IP to seat and will freeflow. That freeflow may be a trickle of bubbles or it may just fail to seat entirely but this is probably the most important note when using the Xstream/Jetstream.