G250V vs S600?

[mahjong]

Can anyone with experience diving both these regs comment on how they compare? The person whose knowledge of regs I respect most, and who has dove and worked on both these regs, insists the G250V was a mistake, a POS. Without a micro-adjust, he claims, the reg's parts need modification, as they just don't fall into place and work together as they did in the old G250.

I have dove both regs, each one several times. So far, I would say that the S600 noticeably delivers more air. However, the G250V somehow cracks and breathes more smoothly. But I also can tell that it doesn't deliver as much air as the S600.

 

[Zung]

I disagree.

The HP replaces the simple and efficient design of the single adjusting knob on the 109/156/G250 with 3 moving parts, all of them made of plastic and require yet another special tool, and 5 o-rings, to achieve what?

"Automatic, Pneumatically-Controlled Anti-Set Feature": this is probably a good thing, even thought the seats last a long time without this feature. I reported 2 cases where the seats sat for 10 years and still perform within specs, here & here.

"Balance Chamber Adjustments": this is probably what you call "micro-adjust". Possibly because of the anti-set, the adjustment of cracking effort is transferred from the orifice to the innards of the adjustment knob. The manual says "turn in the adjustable orifice one turn", then leave the adjustment to the other end. The propaganda says: "the G250-HP can be made to have an even lower cracking effort than before". But how low do you want to go? All my 156's and G250's can be easily tuned to .8" of water, which is well below the case geometry fault, and also the official recommendation of 1.0 to 1.4".

So none of the "innovations" are actually needed. If anything, the HP was a mistake, an attempt to try to sell another reg to the consumer.

 

[elan]

I have 3 250vs and 1 S600 that is upgraded to a metal barrel. All G250Vs crack at around 1" Without a metal barrel and with the anti-set feature (earlier models) the S600 an awful reg. with highly pronounced dry mouth effect and very finicky in cold water. I cannot say one delivers more air than the other (not anywhere close to D series or Air1), they are about the same, ease of cranking I found is more on the G250V side probably because the diaphragm is a bit bigger. The advantage that S600 has is soft purge which helps to avoid stuck purge buttons when you use it on stages and drop it in silty environment. G250V on the other hand has the anti-set feature built into the purge which is great for prolonging the life of the seat.

I found that the older S600 design was really convoluted with a bunch of parts and o-rings. It definitely a "step forward" from a BA in terms of over-complicating the design. I cannot say that the older S600 breathed any better than the BA with BA I still see as a benchmark for simplicity with providing great performance.

 

[halocline]

I have dove both regs, each one several times. So far, I would say that the S600 noticeably delivers more air. However, the G250V somehow cracks and breathes more smoothly. But I also can tell that it doesn't deliver as much air as the S600.

I suspect that what you perceive as 'more air' is an increased venturi assist effect. The S600 case is smaller, which means the same volume of air through the case will be moving faster. The 'smoothness' of the G250V could be due to the larger case, slightly slower moving air, and metal air barrel. Those are guesses.

For sure, though, the poppets and orifice are the same, and basic geometry very similar, so they are likely to have very similar flow capacities if they're adjusted the same and used with the same first stage.

Your perception of better cracking effort in the G250V is interesting, because I believe one of the benefits touted by the S600 was lower cracking effort.

To me they all work fine and specs can be misleading; the center balanced coaxial valve 2nds are noticeably easier breathing but when I get the converted 109s really tuned well they breathe great and they're the lowest on the pole as far as breathing specs go.