Cyclone 300 ( circa 1974) Intermediate pressure concerns re scuba pro octo

[yaml]

Rig: serviced 1st and 2nd stage cyclon 300 ( circa 1974)/ octo scuba pro 2nd stage from MK VII( also circa 1974)
Cyclon hose rated to 508 psi/ octo hose rated to 400psi ( both hoses new)
Question: Poseidon dive shop service guy ( seems very knowledgeable) says my octo is not " rated" to handle the IP of the cyclon / didn't have time to discuss with him; I have used the rig on +/- 40 dives since he serviced the rig using LP steel 120 - typically filled to 2500 - 2600 psi/ strictly recreational diving
Questions: what are his concerns? I thot the IP in the 300 could be anything from 130 - 290; so hose psi rating shouldn't be a problem ; is his concern the internals of the old SP MK VII? If so, what is the risk ? I.e. What can happen? Appreciate the feedback from Poseidon gurus

 

[tbone1004]

@yaml the Cyklon is "supposed" to have an IP of 165. The range it can stand is well wider than that, but if the Cyklon is tuned optimally, the Scubapro 109 will not be quite as happy and you'll chew seats up relatively quick. It wants 135psi, which the Cyklon will handle, but won't breathe as well as it will with the higher IP. With that reg in particular, you really are better off having matching second stages.

 

[rsingler]

What @tbone1004 said.
Cyklon 2nd stage breathing characteristics are really suboptimal at an IP of 135. If I tune my Cyklon to 0.9" at an IP of 165, the cracking effort doubles to 1.8" as I decrease the IP to 130.
Conversely, the SP 109 is receiving quite a lot of pressure on the valve seat (125%) at an IP of 165. It'll degrade the seat much more quickly, and breathing characteristics (valve opening) is quite abrupt.
I wonder which IP your service guy chose?
Me, I would have respectfully declined to service your reg set as delivered. Yes, it works - both regs are bulletproof. But one or more of the pieces are well out of specification, and performance will suffer in the short or long term, depending upon which IP your shop guy chose.

 

[yaml]

Thanks tbone 1004 and rslinger: I knew I was asking the right people :1) I will def ask what IP the service guy set 2) prolly just get a Poseidon octo and be done with it / my other rig is an atomic b2 with Cressi octo : thanks again

 

[tbone1004]

Thanks tbone 1004 and rslinger: I knew I was asking the right people :1) I will def ask what IP the service guy set 2) prolly just get a Poseidon octo and be done with it / my other rig is an atomic b2 with Cressi octo : thanks again

you can find Cyklons pretty cheap on the regular, hell if I got my act together I'd have a couple I'm no longer using and I'm sure Rob may as well.

You should consider just buying your own IP gauge, they're good to have since it can act like a check engine light for the first stage. They're cheap
Deluxe IP Gauge (PSI and BAR)

 

[rhwestfall]

so, would a balanced second (convert from 109 to a 156) perhaps tolerate this as the pressure negates itself with balancing? Just curious what you guys have to say on this....

 

[tbone1004]

so, would a balanced second (convert from 109 to a 156) perhaps tolerate this as the pressure negates itself with balancing? Just curious what you guys have to say on this....

it will probably have better seat life, but will still breathe very abruptly compared to the lower IP.

 

[rsingler]

Balancing would certainly make the valve action smoother. But the S-wing poppet still won't like the extra IP. Somewhere I've got a picture. I'll edit the post if I can find it. The barrel of the S-wing poppet split longitudinally when slam-confronted with 250 psi. I'm not saying that will happen at 160, but the plastic is designed for durability at its spec IP. Fatigue becomes an issue at some point above that.