The size of the JJ MAV is actually what I like most about it, but not enough to actually make me think of abandoning my Sentinel with its' rather bulky but very functional MAVs.
Just to correct some of the "facts" that have been presented in the the thread based on how it actually works on the Sentinel:
1.
When having both onboard and offboard connected, IP of the first stages control which tank is emptied first. This mean that unless your offboard has higher IP than the onboard, gas will be taken from onboard. However, unless you are using the same gas both onboard and offboard there is no way to always know exactly what gas is being introduced in the loop unless the non-used tank is isolated.
The biggest advantage compared to the lovely&tiny JJ-MAV is the fact that both tanks can be connected at the same time. Especially for me that mainly dive in really cold waters it is so much easier to use a tank valve rather than having to fiddle with connectors. On the other hand, using QC4 (or QC6 that I have on my unit in order to be able to share bailout with RB80 divers in my team) is a lot easier than the DIN-connection on the JJ-MAV.
2.
Routing BOV through the Sentinel gas block is a huge NO-NO! The manual clearly state that fact, but obviously I had to try it anyway since it would be awesome in theory to be able to feed both loop and BOV on the same connection.
Already on 10-15 meters it is like sucking on an empty coke bottle, I actually ditched the idea without even trying deeper. It is possible to breath, but only in a very sloooooooow and steady pace. To give an example, a full breath would take roughly 12-15 seconds in order to not breath more than can actually be fed through the gas blocks.
Nothing you can actually stand for more than a minute or two when bailing while perfectly healthy. Imagine bailing and requiring +40 lpm of SAC.
Given that you can't really have both onboard and offboard open at the same time, I don't spend nights sleepless on not being able to feed the BOV this way. I still wanted to be able to have instant access to offboard gas via BOV though and came up with a solution that works for me:
Adding a second QC6-hose that is strapped under the DIL-MAV for easy access, feeding the BOV directly. Hose passes through the box in order to not cause more clutter than necessary. Whenever I need to bail, I bail to BOV. After evaluating and deciding that I could go back to the loop CCR/SCR while feeding from offboard I simply take the time needed to move the offboard connector from BOV to DIL.
Gas switches on BOV-feeder connection is performed in exactly the same way as trained on OC technical diving i.e. team verification before making the actual switch. This time, the switch is performed by replacing the feeding connection and testing breath-ability rather than changing the regulator in my mouth. This way, I can always have instant access to best available BO and this is insured by taking the time when it is actually available i.e. when all is good and calm. In theory, I can even switch gas without taking the BOV out of my mouth. I've tried it as a drill, but I doubt that I'd manage by myself without help from a buddy if I would suffer from an actual CO2-hit with minimum time between breaths. Works like a dream at least to 90m where I sadly had to test the setup for real
The good side is that it didn't disappoint me
This solution works whenever diving with other CCR-divers, but I feel that I lack some speed when diving with OC-buddies. Mixed team diving for me doesn't happen very often and only on relatively shallow dives with limited amount of tanks all containing breathable gas. If I would do deep dives with OC-divers I would really consider adding a second OC-regulator on a long hose around my neck that also is fed through the BOV-QC6. This way I know that as long as I take the needed time to validate during the actual switch I can always get the correct gas to an OOG buddy regardless of amount of stage tanks carried by myself without having to take my loop out of the mouth.
/Jonas
