Mares MR12 users please help...

[nikefreekz]

those using MR12 would know that the 1stage has got 1 HP and 5 LP ports and one of the LP port is marked with the word DFC, the manual says THAT is the preferential port for primary second. but the 2 sets that i bought the second stage wasn't connected to that port, shall i switch it around???

 

[nikefreekz]

anyone?

 

[Jason B]

Yes.

 

[nikefreekz]

so the primary second should go into the DFC marked LP port?

 

[Red Sea Shadow]

Either or. It is preferred to be connected to the marked port. However, connecting your primary second to any LP port won't cause any harm.

 

[nikefreekz]

oh ok, roger that, thanx heap!

 

[Jamdiver]

Hey nikefreekz, I have a Mares MR12 rebel.
Mine has 2 HP ports and 4 LP ports though.

Anyway to answer question, I think perhaps the 2nd stage might breathe a bit smoother using the DFC port or perhaps that's all marketing hoopla?
In any case don't think it makes much difference which port you attach it to.
I think though the next time you get the reg serviced you should just ask them to switch the hoses around so that the 2nd stage is in the dfc port...

 

[John C. Ratliff]

I think this has to do with actual performance of the regular being optimized at this port. The reason would be that there are preferred air paths (and sometimes actual nozzles) that the air flows out of from the first stage. If it goes directly down the LP hose from the first stage valve, then there is less turbulance, and more air will flow down the hose (depending upon both demand and depth). If on the other hand, the air has to impact the side of the first stage case, then it will not flow well, and although it will come out, will not achieve its optimal flow rate. So I would put the second stage that you wanted the greatest performance from on that DFC port.

Now, I do not know the exact makeup of the new MR12 (mine dates from the 1970s), but this is my "take" on this DFC port. For me, I have a converter which makes three ports out of one, and I always put my regulator on the one that flows straight through, and the inflator on one of the other ports.

SeaRat

 

[BigWhiteSquare]

From the verbage on the Mares site: "the DFC system, which minimizes intermediate pressure drop during the inhalation phase."

http://www.lab.mares.com/brevetti.asp?menuSup=4&id=7&lang=eng&codTecnologia=dfc

Sounds like marketing hype, but anyway...

I bought mine new, and that's the port the second stage was using.

___

 

[Greg Barlow]

When I was working for Rodale's, ScubaLab founder, the late Jon Hardy, used to give me ANSTI data on regs that I wanted such info for. The DFC port works much like John Ratliff mentioned. When you remove the first stage diaphragm, you can see an opening. This direct port leads straight to the DFC port orifice. This allows more laminar flow of the gas to that particular port, and consequently allows a lower drop in intermediate pressure. Jon ran a MR12 Akros on the ANSTI simulator a number of times, while alternating the second stage on different ports. In each case, the DFC showed less IP drop than the other ports. It does work as designed, and doesn't use any parts.

I use the DFC port on my MR12 regs whenever the hose layout permits.

Balanced piston regs such as the ScubaPro models also show such laminar flow when the bottom port on the swivel is used. The same gas flow principle is used with the "straight shot" pattern.

Now...When manufacturers start claiming that all of their ports offer such an advantage, you are hearing marketing hype. BTW, when Mares introduced the DFC idea, other companies soon picked up on the feature.

I have several MR12 first stages. They are a great design, that is very small in size. They offer enough gas flow to achieve US Navy Class "A" honors, and will meet the needs of nearly every conceivable dive. I have serviced many of them over the last 10 years or so, and short of sporadic problems with HP seats, they have proven to be a real classic workhorse.

Greg Barlow
Former Science Editor for Rodale's Scuba Diving Magazine