Breathing Resistance- old S.P. REG

[donclaypool]

At ~90fsw, on the Spiegel Grove this weekend, I compared my primary 1st. stage to my octo. and noted, to my surprise, that my octo had less inhalation effort but more exhalation effort than my primary. I've just had them serviced. It's and old Scupapro Mk5 1st and adjustable 2nd, manufactured in the early or mid 80's, I believe, with an Aqualung Octo. I don't worry much, my gear works and I trust it and take care of it. I've always noticed the breathing resistance and have learned to tolerate it. I've mentioned it to the people who service the reg. and asked if there's a solution ( turning up the I.P). My LDS says this model second stage has always been problematic, but the octo was excellent. I've always left the 2nd. stage adjustment open all the way. Also, I don't notice it as much diving nitrox. Does breathing resistance contribute to CO2 retention, or just fatigue?

1. Has new technology- venturi assists, and all the bells and whistles virtually eliminated breathing resistance?

2. Can I gain the benefits of a new reg by replacing only my
second stage.

3. Do I need to buy new regs due to the age of these ones? I stay within rec. limits, but still want an excellent cold water reg. should I move north again. I don't believe in replacing with the newest and best simply for that reason.

I know this reg is the granddaddy of the balanced piston design and all the old commercial guys tell me to keep this reg.

So, I guess I'll do a little buddy breathing on my next dive to compare something newer to mine at depth, or rent some new gear for comparison.

I really don't need to hear "Go get an Apeks or Posideon and forget about it". What I need is a few educated opinions from you old timers and reg rebuilders.

Don

 

[Walter]

You should get rid of that reg ASAP. Send it to me.

Seriously, that is a fine reg, I'd hang on to it. If breathing resistance gets too light, you'll have free flow problems.

 

[ew1usnr]

You can have the adjustable upgraded to a balanced adjustable.

To keep it simple, you can use your US Divers octopus as the primary since it breathes easier, and use the Scubapro as the octopus.

 

[redacted]

An upgrade of the 2nd to a balanced adjustable should give you performance comparable to a G250. Upgrade requires an annual service kit (BA/G200B/G250) which includes the new poppet and balance chamber and a new (lighter) spring. Parts should be on the order of $20.00. Labor might run another $20.00.

But I'm somewhat surprised that the adjustable is breathing that hard. You might want to check cracking pressure in a sink of water. Properly tuned, with the adjustment knob at the stop, I would expect it to start flowing shortly after the knob is submerged and before the zip tie is submerged.

Setup correctly, the adjustment knob should allow you to control freeflows and still provide HP WOB at depth.

 

[donclaypool]

Thank you Gentlemen:

awap once bubbled...
An upgrade of the 2nd to a balanced adjustable should give you performance comparable to a G250. Upgrade requires an annual service kit (BA/G200B/G250) which includes the new poppet and balance chamber and a new (lighter) spring. Parts should be on the order of $20.00. Labor might run another $20.00.

May I order that kit or do I need to take it to a dealer? It was just serviced. Wouldn't it have been upgraded or is that an option one has to ask for? Is "BA/G200B/G250" the part number I need?

I couldn't help myself. I opened her up and adjusted the seat until it freeflowed and then tightened it up just past the point where the freeflow stopped. I also bent the actuator for less diaphragm travel before airflow. I'll try it cautiously this weekend. I can't recommend DIY reg rebuilds but I've made a living working with various regulators (air, steam, refrigerant...) and felt comfortable disassembling this one.

don

 

[ew1usnr]

Having the demand lever closer to the diaphragm will give a more instantaneous response. Changing the seat adjustment just a bit back from free flow will make it more sensitive. Try it out and see how it compares to the octopus now.

 

[DeepScuba]

Yeah, it sounds like the tune-up wasn't up to snuff.

Just because the new parts are in there, and it's clean, doesn't mean it was adjusted correctly.

 

[redacted]

donclaypool once bubbled...

May I order that kit or do I need to take it to a dealer? It was just serviced. Wouldn't it have been upgraded or is that an option one has to ask for? Is "BA/G200B/G250" the part number I need?

I couldn't help myself. I opened her up and adjusted the seat until it freeflowed and then tightened it up just past the point where the freeflow stopped. I also bent the actuator for less diaphragm travel before airflow. I'll try it cautiously this weekend. I can't recommend DIY reg rebuilds but I've made a living working with various regulators (air, steam, refrigerant...) and felt comfortable disassembling this one.

don [/B]

I'll get you some part #s this evening. You will have to go thru an LDS but it never hurts to ask if he will sell you the parts. I'm not a tech but recently decided to try the SP metals. My Mk10/BA seems to perform every bit as well as my G500. I converted an Adj to a BA and it performs great in calm water but has some FF problems in strong current that force be to tighten the adjuster. I picked up another Mk5/Adj that I will try for strong current. I also decided to bend the lever a bit as it was a good 1/4 inch too high and made reinstalling the cover difficult. Works good in the sink but I'm waiting on a new exhaust valve before I can use it.

Sounds like the adjustments you are making are steps in the right direction. On all 3 of my R109's, the lever (actuator) is in full contact with the diaphram. The hardest thing I have found about DIY servicing of 109"s, besides getting a source for parts, is trying to remember what is up on the "S" symbol. It is nice having only 2 O-rings in the 109 Adj versus 13 in my G500.

 

[oxyhacker]

Assuming the 2nd you are talking about is a metal (the G250 came out in the 80's but I can't remember when offhand) 109 then there's a limit to what you can do with it - while most of the parts are identical to the G250, one of the best breathing 2nds ever, the 109 is missing the adjustable venturi boost adjust which is one of the main ways modern regs are tweaked a little further for super easy breathing (I was reminded of this when diving in the keys on a rented Mk2/109 last week I kept cursing the thing for being a pig then midway through the dive remembered it had a venturi lever - kicked it up half way and it was totally transformed!).

Not sure how excited I'd get about upgrading to balanced. Sure might as well do it if you are having it serviced, its cheap and just plain cool to be able to upgrade so old a reg, but I have both balanced and unbalanced 109s which I use interchangeably and can't say I notice a difference. I might give the unbalanced one a half turn on the adjust middive if I'm working hard but that's it.

Sounds to me like what you ought to do is some basic home diagnostics - check the IP and do a water test just to make sure the thing is working correctly, and have it properly tuned if anything is amiss. BP regs like regular servicing, not a whole overhaul necessarily but a quick cleaning and relubing of the piston O-rings, with a good modern lube like Christolube especially, always seems to to cheer them up.

 

[DA Aquamaster]

I have a half a dozen Balanced Adjustables and one Adjustable that has not been upgraded yet.

I assume that you are removing the LP hose to adjust the orifice and cracking effort? When you do this you need to have the purge depressed as well to prevent the orifice from cutting into the seat.

I have never had to bend the lever to get optimum performance. The height of the lever changes with the depth of the orifice and if everything is functioning correctly, the lever height will be correct with no bending required.

A damaged (nicked or flattened) orifice will require more spring pressure to seal against the seat and consequently will need to be screwed in farther. This increases the spring pressure and the cracking effort and also lowers the lever height. If you are having to bend the lever, I would instead inspect the orifice and see how it looks.

A Balanced Adjustable or an Adjustable updated to Balanced Adjustable status will breathe as well as a G250. I also have one that was rebuilt (by someone else) with what I think is the lighter plastic poppet asssembly from the G500/S600 and it is the best breathing second stage I own. Once I use my existing stock of G200/G250/Bal. Adj poppets, I am looking into switching to the newer version. The newer poppet also has a replaceable seat and does not require replacing the plastic half of the poppet assembly just to replace the seat.

Scubapro is very good about sticking with evolutionary designs that allow older models to be upgraded. This is also very good news in terms of continued parts availability. In my opinion, there have been no major improvements in reg performance since the Mk 10 Balanced Adjustable was introduced and most "improvements" involve styling, lower cost of production, or slightly smaller size, but offer very little in terms of improving breathing performance. I would not trade in a properly functioning and adjusted BA for a newer reg.

The Balanced Adjustable had a case that was designed to offer a moderate venturi assist without a flow vane, so the lack of the adjustable flow vane found in the G250 is not a big loss. Anything more in terms of venturi assist and you get a rather unnatural positive pressure assist after the reg starts to flow.

The metal case offers better heat transfer than the G250 which is an advantage for cold water diving. The metal case also allows expired moisture to condense so the air you breathe on the next breath is a bit more moist than with a G250. This goes a long way toward preventing dry mouth.

The original upgrade kits had a new metal purge cover with "Balanced Adjustable" on it. But most upgrades done now just involve replacing the poppet assembly and adding the parts for the balance chamber. The letters on the cover wore off anyway.

The Adjustable and Balanced Adjustable used a variety of rubber purge covers. The early ones (60's and early 70's) had a low rib around the metal "S", the subsequent ones (late 70's and early 80's used a tall rib around the "S" and were theoretically easier to purge. The latest ones are flat in profile with rectangular rather than round holes. The lastest version is less likely to freeflow as nothing extends above the metal purge cover and I prefer them for general use.

The adjustment knobs also went from a low profile knurled finish to a flattened gear tooth profile to the same thing with a rubber coating. The last BA's to be produced (in the early 90's - it was sold along side the G250 for nearly a decade) had a matte finish and the down side of this is most replacement parts come in this finish, so if you replace the purge cover it won't be the same shiney chrome finish as the case on an older reg.