MK25 Evo - Lacklustre quick impression (on the surface)

[Pearlman]

Hello Folks,
I should have completed my first few dives today with my new reg sets but unfortunately the trip got cancelled due to circumstances beyond my control. I noticed an issue more than a month back when my new regs were delivered and I was going to attempt to sort this issue out with an instructor and service tech face-to-face this week after actually diving with them, but looks like any diving wont happen until early June for me.

Short story - I walked in to a local LDS with my brand new regs (1.MK25Evo 2. MK19EVO 3. S600 4. C370 5. Apeks XTX50) to check the IP, and more particularly to see how the Apeks breath with the Scubapros out of the box without any adjusting.

When I tested the brand new MK19Evo with an S600 on a 7ft long hose on the surface for a minute connected to a tank, my first impression was … BRILLIANT! Like easy breathing mountain air that just flows in over-abundance with very low breathing effort. The IP of the MK19 Evo from factory was set at 9.5 bar.

Next I switched to the MK25Evo and the experience was pathetic! The performance was simply anemic and breathing in through the 2nd stage I felt the same anxieties as one feels in a pool with too long a breath hold. In short I have no confidence in this reg when tested on the surface. The experience was the same from the S600, C370 and XTX50. When I sucked in the feeling was one of not getting enough supply, my brain felt starved of oxygen after many repeat attempts (nose pinched) and I can foresee myself experiencing panic if this reg breathed the same at depth and situation becomes difficult. The IP was measured at 8.9bar.

I told myself that the reg would breathe better at depth being a balanced piston, but somewhere I am not convinced. The LDS tech is not an authorised Scubapro tech although was in the past but admitted he struggled with diaphragm regs and had to send it to another city/tech to service it after failing to… so I did not ask him to fix anything given his low skill set in general.

Your thoughts on this and what could be the issue?

In part 2 (tomorrow, it’s late for me now) I will post a video of how counter-intuitive the Magnahelic behaved when a Scubapro-Magnahelic connector mouthpiece was inserted into the 2nd stage mouthpiece (It reversed the effect of the cracking knob).

Thanks for your inputs on this.

 

[rhwestfall]

IP is only one part of the story.... stability across 500-3500 psi is most desired (and not always attainable)... Pistons are the opposite of diaphragms of where you do your ip adjustment).

It is now time to set the orifice on the second stage at a point just shy of freeflow, and then micro-adjust the balance chamber to achieve desired cracking effort. (I know nothing about the XTX50 but assume it to be similar to the c370 and s600 in that it has the micro-adjustor with the balance chamber, and not just the orifice adjustment like the g250)

You tune the second to work with the first....

 

[scubadada]

I have been diving MK25s or MK25 Evos with G250HP, S600, or C370 since 2002. I have never had anything short of excellent performance. Sorry you experience was not as good

 

[davehicks]

It seems like you are evaluating the same 2nd stages on two 1st stages with significantly different IP settings. This is not going to work well. If the higher IP breathes well with the 2nds, you can expect the work of breathing to be worse on the 1st with lower IP. If the 1st with the lower IP did breath well, the 2nds would like freeflow on 1st with higher IP.

Pick a 1st stage and 2nd stage combo and tune them as a matched set. This will give you the best result.

 

[shurite7]

New Apeks second stages need to be tuned, both the crown (cracking effort) and the micro-adjust (magnehelic). Same with all of SP second stages. What I have noticed is new Apeks second stage out of the box are not tuned and will not be easy to breathe from. I’ve dealt with the the issue described above several times and always have to remind new owners and sales people that a new reg set (first and second stages) need to be tuned. Manufactures (I can only speak for SP, Apeks, Aqualung) will set new regs within preliminary settings and leave it to the store/shop techs to tune each of the stages.

When I took my very first reg service class we were told a good tech can tune better than the manufacturer. At first I didn’t get the comment. I’ve since learned and now understand what the instructor was saying, and he was correct. Brand new regs out of the box need to be tuned.

So, in short, I am not surprised at the results listed in the initial post. The expectation that new regs right out of the box should always breathe beautifully is misguided or misunderstood.

 

[rsingler]

This thread is ALL about tuning.
This thread is ALL about dive shop competence.
My guess is that the regs will all perform equally when tuned optimally. Factory QC is currently mediocre even with the big companies, sad to say.

But the tell-tale phrase?
"The LDS tech...admitted he struggled with diaphragm regs..."
That is not a scuba reg technician. That is a parts changer.

Do not despair! Take all your regs to a competent shop and ask them to tune them up.
Boom! Done.

 

[lexvil]

It’s not tuning needed here, in my opinion it’s a psychologist, we are looking at an IP difference of about 9psi and a claim that he can tell the difference with all 3 second stages?? It takes 15 seconds to up the IP of the MK 25 to match the 19.

 

[Pearlman]

It’s not tuning needed here, in my opinion it’s a psychologist, we are looking at an IP difference of about 9psi and a claim that he can tell the difference with all 3 second stages?? It takes 15 seconds to up the IP of the MK 25 to match the 19.

Yeah! Sitting more than a 1000 miles away never having touched the regs I own… a flawless diagnosis! Certainly a psychologist in needed. I concur just not on my side of the continent…

 

[lexvil]