SP S600 vs G250HP

[Agent 47]

What's the difference between these two second stages? Internally they seem to be pretty much the same.

 

[Brules]

AFAIK, they are identical internaly. The outside is the only difference, and possibly the weight? I went with the S600 due to its smaller size/profile, but my LDS told me they breath IDENTICAL. He was trying to sell me the G250. Good shop if I may say so!!!

 

[scubamickey]

I have the S600 and the G250 as my primary and bungeed seconds. Size/weight and price were the only 2 differences I could find. The S600 is lighter and smaller, I much prefer it to my G250 for that reason only. They do breath the same at depth, imo.

 

[DA Aquamaster]

The internals are identical. As indicated above the case sizes differ. The smaller S600 case seems to appeal to many people in an electronic age where cell phones get smaller every year.

But on the other hand the large case of the G250HP accommodates a larger dipahragm that in turn imparts more mehcanical advantage to the system. And the size and weight difference is irrellevent underwater. The G250 is larger and weighs more, but it also displaces more water and the additional bouyancy more than offsets the extra weight. I have not measured it, but I suspect with the increased internal volume and bouyancy, the G250HP is actually "lighter" in the water than the S600 any time it is in use and not flooded.

In any event, both hose lenght and mouthpiece design are far larger factors in jaw fatigue, but it's not considered beneficial for the marketing pukes to admit that.

The G250HP does in my experience perfrom better in very cold water (below 40 degrees) where the S600 is prone to develop a very slight freeflow.

So...your LDS is correct, the G250HP is a much better buy and in extreme conditions is potentially a better performer. Kinda like an old 5 watt bag phone that will connect in the middle of cell hell where new smaller cell phones are totally without service.

 

[Agent 47]

Thanks for the replies. I found some earlier threads on the subject also, after I'd posted. Anyway, I picked up a MK18/G250HP combo. Can't wait to get it in the water.

I still need to get an octo for it. I'm thinking maybe the R190. In the past my philosophy has been that the octo should yield the same performance as the primary second stage, so my thought was to get two identical second stages for pri and octo. I do, however, see some merit in the argument that an unbalanced second stage will have a lower MTBF and thus make a good backup. Any thoughts there? Also, when I eventually go tech and maybe cave I'd like to keep this gear in service, so I'd like to pick an octo that is appropriate to carry over to that world when the time comes, if possible.

 

[Twomixdiver]

I vote for the G250HP, though I think it is more of personal preference. I think this 2nd stage wears better (i.e. looks better) over time.

Those into repair may prefer the earlier version of the G250HP (circa 2000 ????) in terms of ease of service and adjustment.

 

[halocline]

The R190 is a fine secondary...super reliable. It won't breathe quite as well as the G250, but as long as it's tuned to your 1st stage, it will be more than sufficient as an octo.

 

[DA Aquamaster]

I have never noted any difference in terms of mean time between failures between the G250 and R190 as long as they are serviced at reasonable intervals. The R190 has the advantage of using a very simple unbalanced downstream poppet. It's pretty bullet proof.

But on the other hand, the most common problem with a second stage is the development of an excessive seating groove in the low pressure seat. This occurs both from use and from the constant spring pressure forcing the seat against the orifice. In this case, the G250HP would have the advantage due to the use of a much lighter spring in the balanced poppet assembly and due to the adjustment knob that can increase the seating pressure and in all but extreme cases, eliminate the slight freeflow that results from this type of seat wear.

So with the R190, you are more likely to develop the problem if you miss an annual service and if you do it's off to the tech for repair. With the G250HP if you develop the problem, the adjustment knob will get you through your dive trip before service is needed. And that can also be a bad thing as some G250 divers just keep cranking the adjustment knob farther in over progressive dives until they run out of adjutement, and then they miss a dive because thay shoudl have taken the reg in for service several dives ago.

Either way reliability is not really an issue and both will do well if serviced at reasonable intervals.

If/when you go the tech route, you will end up needing a deco reg, and the R190 second stage would work well in that role attached to a Mk 2 first stage which you could by separately later. On the other hand, you save a few % buying prepackaged reg combos, so it would not be all that much more expensive in the long run to get a G250HP now for your backup and then just get Mk 2 190 for deco when you need it. The G250 will breathe much better than the R190, and I think that extra performance is worth having.

 

[Agent 47]

Thanks guys. All good points.

I think I'll go with another G250HP for the octo after all.

Thanks again for all the advice.