Regulator Geeks: Scubapro Mk19EVO - teardown & discussion

[Pressurehead]

Funny, I was only watching that video last night [it is very long an yet to finish it].

Here are some data from the MK19 Regulator Geek Video, where Rob compares the IP swing of various 1st stages from full to empty tank (starting at around 56 mins into the video). The results are shown at 104 mins (screenshot attached below).

The Mk17 has a an 8 PSI swing and the Mk19 Evo 4 PSI. Apparently tolerances in hard parts and o-rings were modified.

Anyway, I do agree with your conclusions and like your reg selection

OK, just bought it in DIN.
Surprised how much cheaper it was at my 'go to' store in Australia.
New toy.

 

[mictrik]

I assume that the MK19 is the same as the MK17 but with the addition of a turret. If that's correct, then my experience is that the MK19 would have a much wider IP swing as tank pressure decreases than the MK25, although it's in the opposite direction due to being an upstream valve. Every MK17 that I've worked on has an IP swing of almost 10 PSI over tank range; i.e if it's 125PSI at 3000PSI, then at 300 PSI it's close to 135PSI. So unless they've changed something in the balance chamber/poppet/orifice arrangement, then the same would be true of the MK19. It's only partially balanced. The MK20/25 in my experience is very good with regards to keeping consistent IP across the supply range, only dropping a couple of PSI.

How much this matters with a balanced 2nd stage is questionable. Probably not noticeable at all to most divers. As you mentioned, they're both excellent 1st stages. I routinely dive with MK5s and 10s, in pretty demanding situations, and they are also only partially balanced in practice. I think this is primarily due to increased clearance between the body and HP o-ring which allows a bit of increased friction at high supply pressures and pushes IP up 7 PSI or so (more on the MK10, a little less on the MK5) at full tank pressure.

Yes. The Mk25 is pretty remarkable with extremely low swing in IP with decreasing or low inlet pressure. The Mk 19 is still very good to this regard and I think it was typically better than what you measured but not by much. I don't remember the numbers. The mk5 dropped more than the mk10 in fact that was the main selling point of the mk10. The mk5 does have slightly higher flow rates however at pressures above 500.
Splitting hairs the MK25 outperforms the MK19 IN flow, response and maintaining IP & flow at low pressure . The latest incarnation the EVO, is proving to do well in very cold water and I think Scubapro should be commended for achieving this without "sealing" the ambient chamber. However, I wish they still had the option of sealing the chamber if only to address very silty, sandy, dirty conditions. The MK25 if left without being thoroughly rinsed can develop corrosion over time that can effect sealing of the pistons head. I have very rarely seen this myself and when I did other parts of the regulator's body was also looking shabby. Others on this board more experienced than me have reported the problem too. I don't think the titanium versions would be as apt to display the issue but titanium is very expensive. All said the vast majority of MK25'S are still going strong after 20 years in service. Add more years for mk10's and even more for mk5's. They are all very simple robust designs and they last.

1. The MK19 will prove excellent all around. Great for deep, cold and or silty conditions even if some of its specs are not up to the MK25 EVO.

Rob retested after someone questioned the numbers, and both the Mk19 Evo and Mk25 were less than 2PSI. I just watched all the videos on Rob's YouTube channel

That is more in line with what I remember. The -9 seemed off. Very stable 1st stage. Just

Rob retested after someone questioned the numbers, and both the Mk19 Evo and Mk25 were less than 2PSI. I just watched all the videos on Rob's YouTube channel

videos on Rob's YouTube channel

That is more in line with what I remember. The -9 seemed off. Very stable 1st stage.

 

[RobPNW]

If I already have a MK17 EVO, will be exclusively diving single tank, and have a long hose configuration, is there really any point in considering the MK19 Evo right now?

 

[halocline]

The mk5 dropped more than the mk10 in fact that was the main selling point of the mk10. The mk5 does have slightly higher flow rates however at pressures above 500.

I think you have that backwards. The MK10 has higher flow rates than the MK5, not by much, but a bigger difference at lower tank pressures. That is very likely due to improved aerodynamics in the piston. And the MK10 has a greater IP swing from full to empty than does the MK5. This is something I've measured many times with many MK5s and MK10s. I believe it has to do with the smaller piston head, which means that the total force on the head is lower, and as a result any change in friction at the HP o-ring will have a proportionally increased effect. And although there's little direct downstream bias in these regs, whatever is there would also have a proportionally higher effect on IP, again due to the smaller piston head size.

 

[Manatee Diver]

If I already have a MK17 EVO, will be exclusively diving single tank, and have a long hose configuration, is there really any point in considering the MK19 Evo right now?

I have a standard Mk17 on my single tank rig, and three Mk19Es (Pony and sidemount sets). I don't see any need to upgrade my single tank rig.

I think the only reason to upgrade is to simply streamline all my diaphragm regs to the Mk19E.

 

[halocline]

If I already have a MK17 EVO, will be exclusively diving single tank, and have a long hose configuration, is there really any point in considering the MK19 Evo right now?

If you don't need the turret (or end port) then I guess there's no real reason. Even if I'm wrong and the MK19 is significantly better than the MK17 in terms of IP stability over the supply range (certainly possible, I've never measured a MK19, just always thought that they were internally identical to t he MK17) then it likely doesn't effect the real-world performance of the reg with a balanced 2nd stage.

 

[Geo7]

That is more in line with what I remember. The -9 seemed off. Very stable 1st stage. Just

Good point, I thought the mk25 was the most stable of all 1st stages...

 

[mictrik]

I think you have that backwards. The MK10 has higher flow rates than the MK5, not by much, but a bigger difference at lower tank pressures. That is very likely due to improved aerodynamics in the piston. And the MK10 has a greater IP swing from full to empty than does the MK5. This is something I've measured many times with many MK5s and MK10s. I believe it has to do with the smaller piston head, which means that the total force on the head is lower, and as a result any change in friction at the HP o-ring will have a proportionally increased effect. And although there's little direct downstream bias in these regs, whatever is there would also have a proportionally higher effect on IP, again due to the smaller piston head size.

Well I never personally compared the two but if you have a catalogue from late 80"s early 90's I am pretty sure that it showed the mk10 at 79scfm@ x psi and the mk5 at 85 or something. The catalog i am referring to also has little magnahelics next to the second stages showing how low cracking effort is. I have to find mine to confirm but maybe someone (no maybes I'm sure many do) has one of these catalogues.

 

[Kupu]

Well I never personally compared the two but if you have a catalogue from late 80"s early 90's I am pretty sure that it showed the mk10 at 79scfm@ x psi and the mk5 at 85 or something. The catalog i am referring to also has little magnahelics next to the second stages showing how low cracking effort is. I have to find mine to confirm but maybe someone (no maybes I'm sure many do) has one of these catalogues.

SP 1989 catalog listed specs:
MK5 flow @ 2000 psig ...87 SCFM
MK5 flow @ 300 psig ...48 SCFM
MK10 flow @ 2000 psig ...80 SCFM
MK10 flow @ 300 psig ...73 SCFM

 

[Geo7]

Funny, I was only watching that video last night [it is very long an yet to finish it].

OK, just bought it in DIN.
Surprised how much cheaper it was at my 'go to' store in Australia.
New toy.

Congrats! And I think it is very newsworthy that the MK19 price has come down. I bet it'll become a common workhorse.