Aqua Lung titan lx supreme or ScubaPro MK 17 C300

[chile7236]

what does this ip swing mean to the average joe/janet when they are on their dive vacation in coz or the bahamas? just curious as i have used the regs mentioned but have not felt that i was "safer" with one over the other.

 

[axxel57]

@chile7236

Have a look on my posts in that thread http://www.scubaboard.com/forums/regulators/449842-aqualung-legend-lx-vs-scubapro-mk25-a700.html

I don't know how to explain it better. If you should not know how different types of 1st and 2nd stage are working, it sounds a bit complicated.

For Joe - Janet in Cozumel it means, if I'm right with my observations, that if they dive for example a MK11 - R195 combination, they will start the dives with a regulator which is breathing significantly harder than in the end of the dive.

I don't think that would be a real safety problem if the reg has been adjusted correctly before, but in the sometimes strong currents of Cozumel one might wish to have his reg working to its capacity from the beginning of the dive and not have to wait until my tank is down to 500PSI .

In this situation I'd rather dive a MK2 - R195 - R295 combination because with this combination I have the best performance of my regulator in the beginning of the dive, not towards the end.

 

[halocline]

@beaverdivers

The link for the other thread is http://www.scubaboard.com/forums/regulators/449842-aqualung-legend-lx-vs-scubapro-mk25-a700.html

Would be great if you would publish your results once you have them. You should have enough opportunity to test some MK11 & MK17

Beaverdivers has neither the knowledge nor inclination to "test" any regulator other than "test market", I suspect.

The question is, what's the potential problem with a 10 PSI IP swing throughout the supply range. An original unbalanced diaphragm USD 2 stage doublehose, the DA aquamaster, was marketed as being "easier to breathe at the end of a dive when the diver is fatigued" as if the IP rise were an advantage. Never let a good design flaw go to waste, I suppose.

My MK5s and 10s, which I love and use all the time, have IP swings close to this in the other direction, depending somewhat on the HP o-ring. The polyurethane 90 duros swing less than the EPDM or viton o-rings. I have never noticed anything during a dive, although I use balanced 2nds.

Far more important than absolute consistency of IP over the supply range, IMO, is the amount of IP drop during inhalation, flow characteristics during heavy demand, and consistent lock up pressure over many dives. This is where the SP piston first stages shine. I have a packed MK5 that I've been using on almost every single tank dive I've made for at least three years, I'm still waiting for the IP to budge a bit before rebuilding. I've seen MK25s go hundreds of dives and several years with no discernible difference in lock up from a newly rebuilt one.

Comparatively, my MK11 is a bit mushy on lock up, but then again I've never rebuilt it and almost never used it, and I got it used. So I don't really know it's history. It looks brand new, but who knows. I need to reserve judgement on it until I rebuild it and use it for a few hundred dives.

 

[axxel57]

[QUOTE
The question is, what's the potential problem with a 10 PSI IP swing throughout the supply range. ][/QUOTE]

Well, the first problem I think is a higher cracking effort of about 0,2 - 0,3 inch/water diving an unbalanced 2nd.

Never let a good design flaw go to waste, I suppose.

Very good!!

I have never noticed anything during a dive, although I use balanced 2nds.

Although? That is why.....

Far more important than absolute consistency of IP over the supply range, IMO, is the amount of IP drop during inhalation, flow characteristics during heavy demand

IMO is the effect of the dropping dynamic IP mostly neutralized by the Venturi Assist kicking in at heavy demand or increasing depth compensation. I would also expect that the flow characteristics are more influenced by the performance of the 2nd stage, not so much by the 1st stage.
The IP drop I was watching for the MK11 & MK17 was between 7 - 20 PSI, whereby the MK17s where surprisingly much better than the MK11, don't know why.
Actually the MK17s I tested where, concerning the dynamic IP, even better than most of the MK10 - MK20 - MK25 I have tested. But okay, I worked on much more MK10-20-25 in very different conditions than MK17, have much more data of them.
What I mean is, you can neutralize the negative effects of the dropping IP, but you can't neutralize the increased cracking effort, caused by a 'balanced' 1st stage which has a relatively high IP difference between empty and full tank, this is why I think I have a point.

And yes, I also prefer the SP piston models for the mentioned reasons.

 

[halocline]

[QUOTE

IMO is the effect of the dropping dynamic IP mostly neutralized by the Venturi Assist kicking in at heavy demand or increasing depth compensation. I would also expect that the flow characteristics are more influenced by the performance of the 2nd stage, not so much by the 1st stage.
The IP drop I was watching for the MK11 & MK17 was between 7 - 20 PSI, whereby the MK17s where surprisingly much better than the MK11, don't know why.
Actually the MK17s I tested where, concerning the dynamic IP, even better than most of the MK10 - MK20 - MK25 I have tested. But okay, I worked on much more MK10-20-25 in very different conditions than MK17, have much more data of them.
What I mean is, you can neutralize the negative effects of the dropping IP, but you can't neutralize the increased cracking effort,

I'm not sure how you're measuring IP drop during inhalation, but if you're using an IP gauge on the LP inflator hose, I think the reason some first stages unexplainedly seem to drop more is due to venturi/air flow characteristics within the IP chamber itself. MK 10s and MK15s drop way more than MK 2s or MK 5s if you measure this way (I do). The only explanation is that there is something in the smaller turret or something else in the 1st stage air flow that causes more pressure differential in the LP inflator hose. No way do MK10s and 15s have less flow than 5s or 2s. Not even close. And because you have a constant volume, flow and pressure are inversely proportional. I think the only way to really measure IP drop during inhalation is with an inline gauge right at the 2nd stage orifice.

I realize that a balanced 2nd stage mitigates the noticeable effect of IP swing from full to empty...that's what I meant when I said "although...." Sorry if that wasn't clear.

I don't think that .2" difference of cracking effort is that important in breathing performance. The real issue in regulator performance is IP drop during heavy demand, and that's even more the case with unbalanced 2nds, because with balanced 2nds part of the force closing the valve is IP. I have found this to be most dramatically demonstrated by the difference in breathing performance of a DA aquamaster vs a Royal aquamaster. It's a really really big difference, and the only thing different is that in the RAM, the IP drops way less during heavy demand than in the DA. You can set them basically at the same cracking effort (at least for a given tank pressure) and the difference in performance is huge, at least with the few that I've worked on. It's a matter of more air flowing smoothly once inhalation is started.

I'm not trying to defend the MK11/17 IP swing, I just don't think it's a performance killer on it's own. In fact, I had no idea until you (or someone else?) measured it that the IP swung that much over the supply range. Nobody has ever complained about MK11/17 performance on any thread I've ever read on this forum. That's an indicator that it doesn't affect performance too noticeably.

 

[axxel57]

I'm not sure how you're measuring IP drop during inhalation, but if you're using an IP gauge on the LP inflator hose, I think the reason some first stages unexplainedly seem to drop more is due to venturi/air flow characteristics within the IP chamber itself. MK 10s and MK15s drop way more than MK 2s or MK 5s if you measure this way (I do). The only explanation is that there is something in the smaller turret or something else in the 1st stage air flow that causes more pressure differential in the LP inflator hose. No way do MK10s and 15s have less flow than 5s or 2s. Not even close. And because you have a constant volume, flow and pressure are inversely proportional. I think the only way to really measure IP drop during inhalation is with an inline gauge right at the 2nd stage orifice.

I'm measuring the IP drop with a working station connected to a flow module. The more air is flowing through the module the more the dynamic IP is dropping, I can watch this.
The reason for different IP drops in one brand is usually the main spring fatigue in the first stage.
The drop is getting bigger from service to service. If the IP drop is getting too high, I have to change the main spring, that solves it usually.

I don't think that .2" difference of cracking effort is that important in breathing performance. The real issue in regulator performance is IP drop during heavy demand, and that's even more the case with unbalanced 2nds, because with balanced 2nds part of the force closing the valve is IP.

Okay, if you consider a 0,2 - 0,4 inch/water not very important in a breathing performance, especially if this higher cracking effort would not be there to this extent if the SP 1st stages (MK11 - MK17) would do their job as all other diaphragm 1sts are doing, then you probably also have a clear argument why you should buy a MK11 instead of a cheaper MKII.
Your 'real issue in regulator performance' is an issue. What do you thing the lower dynamic IP is causing, if not principally an even higher breathing resistance? And this is what I can watch until the Venturi assist is kicking in, lowering breathing resistance until the Venturi Override is bringing the inhalation resistance in the positive inhalation area ( so there is no breathing resistance. Correct, balanced 2nds are less influenced by the static or dynamic IP drop.

I have found this to be most dramatically demonstrated by the difference in breathing performance of a DA aquamaster vs a Royal aquamaster. It's a really really big difference, and the only thing different is that in the RAM, the IP drops way less during heavy demand than in the DA. You can set them basically at the same cracking effort (at least for a given tank pressure) and the difference in performance is huge, at least with the few that I've worked on. It's a matter of more air flowing smoothly once inhalation is started.

I did not really understand what you wanted to say with your example of the DA and the Royal, but if you were referring to a possible 1st stage Venturi assist in one of both, then I agree that this will lead to smaller dynamic IP drop and so to a better breathing in greater depths or strenuous conditions.

I'm not trying to defend the MK11/17 IP swing, I just don't think it's a performance killer on it's own. In fact, I had no idea until you (or someone else?) measured it that the IP swung that much over the supply range. Nobody has ever complained about MK11/17 performance on any thread I've ever read on this forum. That's an indicator that it doesn't affect performance too noticeably.

Well, any first stage has only one main work to do, to produce an IP as stable as possible.

If my observations are correct ( still waiting for some more data) I repeat myself.

If whichever balanced 1st stage is producing an average IP difference which is so close or the same to the IP difference of whichever unbalanced 1st stage, I think it is a substandard product, even if the buyers love it. Up to which IP difference between full and empty tank we should consider a 1st stage balanced?
For me speaks the fact that not more divers are complaining for the good marketing work SP is doing.

OTOH, who of us could tell the difference between breathing the D Serie 2nd with a MKII and breathing a MK 25 with a D Serie 2nd, probably hardly anybody.

And this is what they know exactly at SP.

 

[Fishpie]

.....one more.
Older satin 17 with rubber coated yoke.
Serviced 3 years ago and used half a dozen times since.
3000psi ... 135psi
600psi ... 140psi

edit....got the pressures reversed....corrected

 

[axxel57]

@fishpie

Thanks for sending the data.

If it's a MK17, strange that the higher IP is at full tank.

Normally should be the other way round.

 

[Fishpie]

You're right, my mistake......wrong way round.
140@600 and 135@3000

 

[elan]

I serviced mine recently and it was 135-142

Speaking of MK11 vs MK2.
The only advantages of the former for 0-100ft diver that I see, given a balanced second, will be working better in very cold and/or muddy water and the fact that the reg has the DIN/Yoke perpendicular to the body which slightly reduces the profile.