D420! How about that?

[tridacna]

Back to the original thread...
Waiting breathlessly for @tridacna 's in-water comparison (post #254). It's always wise to get a second opinion around docs...

You can let your breath out Doc.

I spent about 90 mins at 10ft with a Mk17 (not EVO) then a Mk25EVO with the same 3 second stages. Used a D420, G260 and S620T. All new. Nothing scientific. No specific method. Nothing repeatable and no record keeping. Just breathed them to see how they felt. All cracking at a hair under 1”. 1st stage IP at 135psi.

My lousy single “blind” scientific method: I use the same mouthpieces on each. I have a buddy randomly hand me a different reg while keeping my eyes shut and seeing if I could tell the difference while swimming in different positions. Each breathed really well. (I’m in a pool -duh). But...when on my back looking up the D420 was definitely the easiest breather of the three. Totally dry and OH SO EASY. The other two were good but the D420 is absolutely effortless. In fact, effortless in any position. There was nothing I could do to make it feel any different. I absolutely loved it. All I can say is thank heavens for keyman pricing because after about 10 years of trusty service, my G260 is now my octo. D420 is my new primary. Will probably use it mostly with a Mk25 because I’m a piston guy. Mk17 for NJ sandy wrecks and inlets.

Rob is spot on regarding performance! Next week, I’m going to compare to a D350 and D400.

 

[Newdiv]

My rumor source told me the mk19/d420 is going to be available April 2020.

 

[CarcharodonCarcharias]

Meanwhile, I PM'ed @tbone1004 (one of my trusted cavers) about this turret vs right angle connector controversy.
He feels pretty strongly that the right angle connector is a less reliable failure point. He notes stripped threads and connector issues , because the right angle includes a swivel. So it's more than one internal connection. Additionally, he points out the ability of the turret to rotate slightly under certain air sharing conditions.
Bottom line? It looks like I shouldn't use my XStream, much as I like Poseidon first stages. So for me, my twinsets have Deep6 turrets right now, and I'm still going to keep looking for that Mk19.
@buddhasummer , put me down for two Mk19/D420's as you ponder a bulk purchase.

Always nice to wake up in the morning to read something information over a cup of joe. @tbone1004 definitely knows his stuff when it comes to tech diving.

??!!
The MK19 might be similar to the MK18, but definitely not to the MK17.
They are both dry diaphragm 1sts, but pretty different once......
On the Flow Bench they show (almost) the same values concerning balancing and dynamic IP, given the fact that the MK17 is supposed to have high flow ports a bit surprising....
So the only difference in performance I see is the turret......

@axxel57 beat me to the punch.

My rumor source told me the mk19/d420 is going to be available April 2020.

Maybe just in time for ADEX Singapore? That will be interesting. I've yet to see any mention of D420 in SE Asia. I've got a feeling that it will be a tad bit difficult to find it in the region. People here are still stuck in the MK25 and S600/620 configuration when it comes to SP.

 

[Centrals]

I can wait so service my futur regs myself!! I think it’ll be part of the fun!

It is!!

 

[Centrals]

in the diaphragm regulator category, and the Mk19 seems to be a little bit better. Before switching over more equipment to either Apeks or Poseidon, if I can be happy with a Scubapro offering then that is almost certainly the direction I will go. If the only way that I can go down this road is to service the regs myself then I will do that. I still want to try a Poseidon XStream and possibly an Apeks XTX 200, XTX 50 and MTX on an actual dive but this Scubapro solution may allow for me to keep costs in check while still satisfying my OCD.

I know nothing about MTX but rest of Apeks 1st and 2nd stages are very easy to service because I can do it.
Getting the service kits in USA could be tricky.

 

[Centrals]

Maybe just in time for ADEX Singapore? That will be interesting. I've yet to see any mention of D420 in SE Asia. I've got a feeling that it will be a tad bit difficult to find it in the region. People here are still stuck in the MK25 and S600/620 configuration when it comes to SP.

Most of them believing that performance is directly related to the cost! Suckers.

 

[Couv]

read my signature.

I have it memorized.

 

[Luis H]

Rob, no I don't have it.
I checked again my data, and it seems I looked wrong. Sorry!

There was a difference in dynamic IP at 10 SCFM Flow for both 1sts..

MK17: 143psi IP at 600psi tank pressure, 137psi IP at 10 SCFM Flow
MK19: 145psi IP at 600psi tank pressure, 132psi IP at 10SCFM Flow

So that's a significant difference in performance, probably not for the diver if he dives a balanced 2nd (+0,1 inch/h2O), but with an unbalanced 2nd that would translate in 0,1 to 0,3 inch/h2O more Cracking Effort in comparison to the diver with a balanced 2nd.
Still I don't believe that a longer (within a 1st) or bended air path has any practical influence (or loss) on the performance of that 1st.
The venturi of the high flow ports, yes, but how could a very little longer or bended LP air path effect the performance, and which performance?

I haven't had time to follow this thread much, but this just caught my attention.

Just keep in mind that dynamic IP and Cracking Effort cannot happen at the same time (they are mutually exclusive). Cracking effort is (by definition) occurring to initiate any flow. There is no flow (and therefore you have static IP) when you initiate the opening (or "crack") the demand valve.

Once there is flow and the IP tends to drop (we define this as the dynamic IP), but at that point the demand valve is "cracked open" and any self respecting demand valve design would have some veturi flow assistance.


Also the entire subject of long air path and bends on LP air is really a non-issue. Teck divers use 7 foot hoses and they don't complain about it. I have used a 50 foot and 100 foot hose many times with plenty of elbow fittings and have never felt any difference with any extra elbows etc.

Any minor dynamic IP fluctuations would only make a difference with a poor performing unbalanced second stage. Where the "poor performance" (poor venturi assist) is more significant than pneumatically balanced or not.

 

[Scubagaskets]

I know nothing about MTX but rest of Apeks 1st and 2nd stages are very easy to service because I can do it.
Getting the service kits in USA could be tricky.

Why tricky? Look at this link? O-rings for Apeks gear from Scubagaskets

 

[buddhasummer]

I know nothing about MTX but rest of Apeks 1st and 2nd stages are very easy to service because I can do it.
Getting the service kits in USA could be tricky.

I'll ship them cheaply anywhere in the world.