Mk17 vs Mk17 EVO

[ScubaBros]

I have made 0 false statements.

In all seriousness what issue are you having with your pilot?

 

[ScubaBros]

So should I be tuning and setting IP on both my first (MK17 Evo) and second stage G250s at 500psi tank pressure? Cheers.

As per SP technical instruction... if you aren't trying to catch me in saying 2nd stages have an IP haha... if we are trying to get optimal performance at lower tank pressure.. IP is set for the lower tank pressure and is where also to tune the 2nd stage to its desired cracking effort.

 

[ScubaBros]

You've mentioned a few times that you're knowledgeable about how regulators work, and you've mentioned a few times that the rise in IP over the supply range for the MK17 is a deliberate enhancement. So, why don't you explain how SP implemented this rise in IP? What did they do to the design to achieve it? Are other manufacturers doing this, or is SP the only one? And if a 10PSI rise in IP over the supply range is an enhancement, why not go for 20PSI? Wouldn't that be even better? How would you achieve that?

I would also be curious about any tuning tips you might have for the pilot, if you're so inclined as to share those. I could use some help tuning my pilot. There's a thread about it:

Scubapro Pilot

Nobody is criticizing you in this thread because you're a SP dealer. We are criticizing you because you are making false statements about regulator function. So, prove all of us wrong and write something that demonstrates real understanding of regulators. These threads tend to be a little chippy, but they are more-or-less self moderating in that BS gets called out and true statements tend to get affirmed pretty quickly.

I thought you guys didn't like sales pitches haha. But Id be happy to talk about 17 function.

 

[halocline]

I have made 0 false statements.

You've said, a few times, that the IP rise over the supply range in the MK17 is a deliberate performance enhancement. I believe that statement to be false. You have made other statements about regulator function that indicate you don't really know what you are talking about. For example, confusing IP creep and IP stability over the supply range.

You can live in a fantasy world and deny this all you want. Or, as I suggested, you can prove your statements by answering the questions in my previous post. You come up with real answers and I'll happily apologize.

With regards to the pilot, I suggest that you read that thread and see if you have anything to contribute to it.

 

[halocline]

[QUOTE="ScubaBros, post: 7922970, member: 425592"But Id be happy to talk about 17 function.[/QUOTE]

So do it. Quit your BS and actually write something that contributes.

 

[ScubaBros]

Contribute to what at this point. This thread is so splintered I don't even know what we are talking about anymore.

Many of you have said you don't believe what I have stated, which is straight from SP.

Do you think all the money SP has spent on engineering, testing, and development means nothing? Are you better at reg design and builds than they are? That's incredible....

I have no reason to disbelieve SP. I think some of you are lacking in the reg understanding or what I'm saying wouldn't be quite so outrageous or false. But that is all a matter of differing opinion.

 

[Scuba Tiger]

I believe you when you say you are only passing on sales pitches....oops I mean 'product information' from the higher ups at SP, so I will explain to you in clear terms why the bit about the rise in IP being a deliberate enhancement is ********.

1. It doesn't make the reg easier to breathe at the end of the dive. If anything, it just makes it harder to breathe at the beginning of the dive. I hope you understand that you can only tune the 2nd stage for maximum performance to the higher IP. What this means is that the 2nd stage is essentially 'de-tuned' at the beginning of the dive. This would be much more noticeable with an unbalanced 2nd stage.

2. A balanced 2nd stage compensates for changes in IP by increasing/decreasing the cracking effort through pneumatic pressure sourced from IP. (You do understand this, right?) Which means as the MK17 is so brilliantly increasing IP throughout the supply range (like 40 year old double hose regs), the balanced 2nd stage is simply diverting that higher IP and using it to increase cracking pressure.

3. There is no evidence at all that divers would benefit from 'easier breathing' at the low end of the supply pressure. If anything, the reverse would be true. On most dive profiles, the first part of the dive is the deepest, and the last part is the shallowest. Why would we need increased regulator performance on the shallower portion of the dive? The idea that divers get fatigued and possibly winded towards the end of a dive is nonsense. It's not a race or a hill climb.

4. The job of a 1st stage is to provide constant, reliable IP to the 2nd stage. An ideal 1st stage will do that at all supply pressures, and will experience very little IP drop under high demand. This is what makes the best 2nd stage performance possible.

Ok? Go tell this stuff to the SP higher ups, see what they have to say about it. While you're at it, please tell them they were wrong to abandon the D series, and ask them if they did so because too many dumb dealer service techs couldn't figure out how to work on them.

1. I think the difference in performance of a balanced Scubapro setup start to finish is only really going to be noticed by a machine, much less the lay-diver. But if I were to have a preference I'd probably prefer the IP to climb as tank pressure drops. There are more than just 3000 psi tanks in the world and SP services a global market. These things arent designed to operate in a vacuum. Not to mention I'd like to see a first stage that can maintain a fixed IP at any tank pressure throughout a dive. That seems like it'd be some fancy expensive magic right there, but admittedly I'm no engineer.

2. I thought you just said that 2nd stages are tuned for max performance at highest IP? If it's tuned for max performance at highest IP then how can the cracking effort have increased?

3. I like my performance consistently good throughout supply pressure.

4. Um ya pretty much. See #1.

I think quite a few of you admitted to owning multiple Scubapro regs so I'd imagine the engineers have it down. The D series is a pretty cool reg. I'd agree that alot of techs being parts replacers probably contributed to it's demise. You can have the coolest slickest high performance reg there is, but if techs cant work on them then it doesnt really matter. Unfortunately in the real world not everybody is a great tech for whatever reason.

 

[eelnoraa]

I like technical discussion. So I will continue in that aspect only.
1. Regulator operation is by the concept of negative feedback. When regulation is not perfect, there are two types of error. 1)Systematic error, and 2) random error. Random error has to do with things can't control, such as the manufacture tolerated, etc, which can never be eliminated. Systematic error has to do with the design topology. In this case, Mk17 has a systematic error in design, meaning even the random error is zero, IP will still vary as tank pressure within the operation range. On Mk25 or AL legend, the systematic error is 0 with respect to tank pressure. (AL has a systematic error with respect to depth). They do have fixed IP across tank pressure as long as tank pressure is within operation range. So it is not difficult to do, not super expansive. It is the concept of the design.

2. If 2nd stage is turned for max performance at highest IP (Mk17 @ 500psi), then if IP is lower (at full tank), performance may suffer, right? That is what Halocline is talking about. With Mk25, you turn 2nd stage for max performance, and it stays that way across tank pressure because IP doesn't change.

3. For all practical concern, Mk17 is a good performer throughout tank pressure because the change in IP is still small especially couple with balanced 2nd stage. But from engineering and technical point of view, it could be better. I think what pisses people off is SP market the design limitation as a feature. But it is also not unique to SP. AL also market their design limitation as "over balanced". Think of electrical car like Nissan leaf with 80 mile range, but if Nissan market it as a feature to enable driver to take a break after driving for a "proper" distance. Of course Nissan didn't do that.

 

[Scuba Tiger]

Thems alot of fancy words man...

1. IP increases as tank pressure drops on all balanced Scubapros. The Mk2 decreases with drop in tank pressure.

2. You tune all Scubapro seconds at 500psi because that is where IP is highest. Obviously on Mk2 this isnt the case but I've never seen a difference provided the Mk2 was within spec.

3. Everything could be better from an engineering and technical standpoint. How much do you want to pay for a first stage. Scubapro doesnt market or tell us to market IP inversion as some kind of feature to sell regs. They educate us as techs so that we know whats happening with a reg and can ensure that it's within spec.

 

[halocline]

...Not to mention I'd like to see a first stage that can maintain a fixed IP at any tank pressure throughout a dive...
...I like my performance consistently good throughout supply pressure.

Howdy! I wonder if you're scubabros' bro. Anyhow, my post that you replied to was debunking Scubabros' contention that the rise in IP throughout the supply pressure range is a deliberate performance enhancement. It seems that you apparently agree with me in that the rise in IP is not an enhancement; that in fact a steady IP throughout the range is preferable. Even though I doubt that was your intention, thank you!