[Q] AL Calypso vs. SP mk2+ R190

[pains]

I'm looking for regulators for me and my wife.

We usually do 20+ dives a year almost at tropical sea. We dive deeper than 100 ft but 130 ft is the limit. All dive is recreational level. We do not have any plan to go TEC or ice (< 40F) diving.

Our candidates are Aqualung Calypso and Scubapro MK2+ R190 due to easy worldwide maintenace and price. I've searched this board and found that although there are entry level equipments but good for recreational diving.

But SP mk2+ R190 does not have enough air flow when used with 2 persons. I hope not to have this situation but the possibility is there. How's Calypso? Same with mk2+ R190? Or is it good with 2 divers?

If all is not good for buddy breathing I can choose SP mk11 R190 with 20% more money. Then can I get no wet breathing when upside down? Is water invasion when inverted bacause of 1st stage or 2nd stage?

 

[DA Aquamaster]

The Mk 2 Plus first stage has a flow rate of about 92 SCFM. The R190 and R295 second stages found with the Mk 2 Plus only flow about half that anyway. So unless you are both fully depressing the purge valves on your second stages at depth (in which case you are not breathing anyway), the Mk 2 Plus will supply enough air to support both divers at 130 ft.

The performance of the Calypso is very similar to the Mk 2 Plus as they are nearly identical designs although Aqualung does not supply performance numbers.

You can go with the Mk 11 as its flow rate is about 175 SCFM, but the big avantages are that it is balanced and would offer better performance at low tank pressures, and would better support a higher performance second stage.

If buddy breathing at depth, the donating diver can lessen the impact on the first stage by inhaling when the OOA diver is exhaling.

Wet breathing when inverted is due to some water slipping past the exhaust valve during the exhale cycle. It falls to the top of the inverted case where, since it is near the mouthpiece, some of the water is carried into the air being inhaled. It is pretty common with most regulator designs. Side exhaust models like the Poseiden Jetstream do not have this issue, but they have a similar issue when the side with the exhaust valve is elevated.

 

[pains]

Thanks DA Aquamaster.

I could stay entry level equipment and save money. Personally I prefer AL Calypso to SP mk2plus R190. Easy breathing and better mouthpiece. But SP has better resale value here.

 

[squidster]

I have Scuba pro MK 11/R395 really good reg and priced at a level that most can afford,its more compact then the 2 you are looking to buy.
easy reg to pack when traveling.
i have a calypso and have used a scuba pro mk 2/r295 ,my choice would be the mk2

 

[halocline]

But SP mk2+ R190 does not have enough air flow when used with 2 persons. I hope not to have this situation but the possibility is there. How's Calypso? Same with mk2+ R190? Or is it good with 2 divers?

If all is not good for buddy breathing I can choose SP mk11 R190 with 20% more money. Then can I get no wet breathing when upside down? Is water invasion when inverted bacause of 1st stage or 2nd stage?

I don't think you have a clear understanding of the flow capacity of the reg or typical requirements. The MK2 could theoretically drain an entire tank in a minute, just like any decent 1st stage. (AL80 has 80CF of air, MK2 flow rate 90CF/minute) So, I doubt you'll have a problem getting enough air out of it.

The "wet breathing when upside down" bit is a 2nd stage issue; my R190 does not breathe wet upside down, but I have no experience with the aqualung so I can't say anything about that one.

 

[Luis H]

I don't think you have a clear understanding of the flow capacity of the reg or typical requirements. The MK2 could theoretically drain an entire tank in a minute, just like any decent 1st stage. (AL80 has 80CF of air, MK2 flow rate 90CF/minute) So, I doubt you'll have a problem getting enough air out of it.

I totally agree with you and I tend to think the same way when I read those large flow rate numbers in relation to cylinder gas capacity.

That also makes me wonder how they figure out the flow rates. The flow rate on a first stage valve (fully open valve) is proportional to the source pressure (tank) pressure. Therefore, is the flow rate the maximum calculated (or measured) with a constant maximum pressure source or is it at an average tank pressure?

It also seems like all the LP ports have to be open to ambient (with no hoses, etc.) to minimize flow restrictions. Heck, I don&#8217;t know if tank valves can support that flow rate.

Even if the average flow rate is actually half of advertised (approximately average), it is still way more than needed. The limiting factor is normally the second stage.

 

[DA Aquamaster]

The orifice in the second stage is the limiting factor in some second stages (G250 for example)while the aspirator port(s) (R190, R390, etc) are limiting factors in others and in either case pose much more of a limitation on flow rate than even a low performance the first stage.

One thing that also comes into play is the tank valve itself as all of them have relatively small gas passages and/or dip tubes with small passages. This is particularly true with older valves where the end of the dip tube was flattened and then had a small hole drilled horizontally through it. It made it harder for dirt or water to enter, but (or perhaps intentionally) greatly reduced the flow capacity of the valve. Another factor that can come into play to restrict flow rate may also be ice forming inside the valve passages. I have yet to see the tank valve that will dump an AL80 in less than 2-3 minutes.

Scubapro tests their first stages by connecting them to a constant pressure air supply and then removing one of the LP port plugs (which ever one flows the most - the end one in the Mk 25), so that no valve, hose or second stage restrictions are present - so in a sense they say very little about real world performance and serve only to provide reference points between various models and to perhaps to help identify some minimum levels of performance.

Most technical divers used to regard the Mk 10 as the minimum in terms of performance that was adequate for any technical diving situation. SP used to rate its flow rate as some where in the 120-150 SCFM range depending on the seat and piston that was installed, so anything more than that is pretty much gravy.

Beyond that, IP stability, IP drop and response time also play roles in the qualitative side of breathing performance.