Scubapro s600 vs r156

[Bearded_fire_worm]

I just bought a set of new and latest versions Scubapro s600 & mk17 regs, i also have a mk25 evo that i bought by itself. My question is what second stage will be a more capable cold water second to pair with the mk17? The s600 or an all metal 156? My understanding is all metal regs would be better. If that is the case i'll instead put the mk25 with the s600 and a 156 for an octo and have the mk17 with a 156 and a 109.
Would the s600 and mk17 be tuned together at the factory or just put together later after being set?
Any suggestions?

 

[axxel57]

General understanding here is that 156er and 109er are very difficult to get frozen to a problematic extent, so concerning the freezing issue you should be right thinking about putting a full metal 2nd on your rig.

Only 'disadvantage' might be the pretty small exhaust valve of the 'Full Metals', which probably could increase the WOB while working hard underwater.

Maybe Luis H. or other 'usual suspects' get in to clarify, they have an excellent understanding of the functioning of 'vintage regulators'.

 

[Tbar]

Have a look at this http://www.scubaboard.com/forums/archive/index.php/t-277996.html. And I am sure there are many other threads.

Your new s600(s) should have the metal barrels.

How cold?

 

[halocline]

While the metal air barrel in the S600 would certainly help, I suspect that the all metal case would be far better in terms of heat exchange. Personally I like diving with them regardless of the water temp (I couldn't find cold water around here if I wanted to) because the metal case provides some condensation which warms and moistens the air. I also like the fact that the 109/156 (no "r" by the way) has a bigger case, which means slower moving air in the case, and there's a less pronounced venturi effect, both of which I find more comfortable. The old metal SP 2nds are just very enjoyable regulators to dive with under any circumstance.

It's certainly likely that the s600 does better on WOB test machines, but since I personally am not a test machine, I don't really care what it would prefer.....

 

[ams511]

I am not sure if Scubapro sets first then assembles or sets after assembly. Usually a reputable LDS will check the regs before selling them. If you have an intermediate pressure gauge them I would check the IP of MK-17 and match the MK-25 to that. Unlike older Scubapro piston regulators the MK-25 does not use shims to adjust IP.

 

[Bearded_fire_worm]

Well the coldest water that i would be diving will probably only be in the mid 40's so i probably don't have much to worry about using either set of regs in that temperature.
I do have an intermediate pressure gauge and the IP of the mk25 is 135 and the mk17 is at 140. I thought these would have been set the same.
How is the pressure set in the mk25? Anyways i can't wait to dive them but luck or lack of it would have it that i have come down with a cold now.

 

[halocline]

Well the coldest water that i would be diving will probably only be in the mid 40's so i probably don't have much to worry about using either set of regs in that temperature.
I do have an intermediate pressure gauge and the IP of the mk25 is 135 and the mk17 is at 140. I thought these would have been set the same.
How is the pressure set in the mk25? Anyways i can't wait to dive them but luck or lack of it would have it that i have come down with a cold now.

At what tank pressure did you measure IP? The MK17 will rise about 10PSI (I can't remember the exact amount) over a normal supply range from 3000 to 500 PSI. The MK25 may drop a couple of PSI over the same. So if your tank was near empty when you measured IP on both regs, I'd say they were about set equally. I guess if you wanted to get picky you could set them the same at about 1700 PSI, roughly the middle of a normal dive range. If you use HP tanks, maybe bump up the mid point to around 2K PSI.

But, it doesn't matter much for either the S600 or the balanced version of the metal case. They will compensate for the difference in IP up to a point. So just put together the 1st and 2nd stages you want, and try them. If they're not breathing the way you like, you can easily adjust the orifice slightly. Lots of folks on this forum can talk you through it.

 

[Bearded_fire_worm]

The tank pressure was about 1500 when i took the IP reading for both.
Not sure if my s600 is set too tight, it's easy to induce a free flow by turning the knob all the way out then pressing the purge.
My 156's don't do that with the knob turned out.
I have rebuilt my 109 with an upgraded poppet, balance chamber and spring, O'rings on the orfice and adjustment knob. What i do when i set the orfice is tighten it up until it leaks air with the adjuster turned out completely then i loosen till it quits leaking. I also push the purge in when turning the orfice. So before starting a dive i turn the adjuster in so as to avoid free flows. Then adjust it out while under. I do know the inner workings well on the 109 and 156.

I guess i'll have to dive to really see if the s600 breathes as i like, just breathing from it above water isn't quite as easy as my 156's though in both inhalation and exhaling.... maybe because it is new?

 

[halocline]

The tank pressure was about 1500 when i took the IP reading for both.
Not sure if my s600 is set too tight, it's easy to induce a free flow by turning the knob all the way out then pressing the purge.
My 156's don't do that with the knob turned out.

That's fairly normal, the S600 has a stronger venturi assist which will get the free flow going. Try turning the VIVA to minimum and see if it still free flows when purged. The 156 has no adjustment for the venturi assist, and it is not nearly as pronounced. That's one of the things I like about them; you don't get the feeling that fast moving air is being pushed into your throat.

If you want to really match the IP on the two first stages, I would lower the MK17 IP by about 5PSI so they are both 135 at 1500 PSI. Then get your tank filled, check the IP with a full tank. The MK17 will be noticeably lower. Then turn off the tank valve, bump the purge a bit until the pressure gauge reads about 4-500 PSI, and check again. You'll be surprised.

 

[Bearded_fire_worm]

Thanks, all i have dived with are my 156's, 109's, an r190 and r295's. Never with a current higher end second with viva and adjustment.
I induced a free flow with the VIVA at maximum and adjuster out, when i closed the VIVA it stopped immediately and i couldn't get a free flow to happen with the VIVA at minimum.
Definitely don't want to dive equipment i don't know the ins and outs of.

I do see that the IP has increased a little as the tank pressure has gone down on the mk17.