Scubapro MK 20 creeping badly

[WantSomeScuba?]

Only for their diaphragm regs. My understanding is If you set a piston reg at 145 at low tank pressure you're likely to be out of spec (above high) at full tank. My MK10s seem to swing 5-10 PSI. If I set at 145 at 500psi ip will be at around 155 at 3000psi. So you'd set ip at 3000psi.

I was under the impression that you set the newer "over-balanced" piston regs at 145 @ 500 PSI (for example, a MK25 EVO). And I'm using Scubapro's definition of overbalanced. It should be lower at 3000 PSI for those models.

 

[buddhasummer]

I was under the impression that you set the newer "over-balanced" piston regs at 145 @ 500 PSI (for example, a MK25 EVO). And I'm using Scubapro's definition of overbalanced. It should be lower at 3000 PSI for those models.

You are correct, on the MK25 apparently an ip inversion of 1-5psi can be expected. Thanks for pointing out my error.

 

[buddhasummer]

I was under the impression that you set the newer "over-balanced" piston regs at 145 @ 500 PSI (for example, a MK25 EVO). And I'm using Scubapro's definition of overbalanced. It should be lower at 3000 PSI for those models.

I'm assuming it's the same for a MK20, what about a MK15? Cheers.

 

[redacted]

I was under the impression that you set the newer "over-balanced" piston regs at 145 @ 500 PSI (for example, a MK25 EVO). And I'm using Scubapro's definition of overbalanced. It should be lower at 3000 PSI for those models.

A marketing spin on an engineering solution to a design limitation of a BP 1st.

 

[WantSomeScuba?]

I'm assuming it's the same for a MK20, what about a MK15? Cheers.

Honestly, without schematics in front of me, I'm not 100% sure. Lemme check on Monday.

 

[halocline]

It's only the latest piston that has a slight flare that could result in a few psi IP rise at lower supply pressures. I have a MK20 with the new piston and I've never noticed it, so....

MK15 definitely not, and MK20s with all earlier generations of pistons, to my knowledge no increase in IP as supply pressure falls.

The flare in the piston is not to deliberately increase IP, it's as awap mentioned, it is an attempt to compensate for the slight downstream bias in the balanced piston design. I wouldn't bother considering it for setting IP, just set it where you want it. It's not like an unbalanced flow-by piston that has a 20PSI swing or even the MK11/17 that is an only partially balanced upstream diaphragm design and swings 7-10 PSI or so.