to upgrade an 109 to BA

[buddhasummer]

Thanks to all of you for the comments.
I am aware about the sufficiency of one balanced part, be first or second but it is good to reiterate this for people who think they need the last "top of the range" model.
The upgrade is more like a discovery exercise and to be in touch with @buddhasummer again

Message sent.

 

[Angelo Farina]

This spring, during the lockdown, I upgraded all my 109s to the latest S-wing poppet, and the curly-feets lever for those who did not have them yet.
The combination of these parts makes the regs much smoother to breath. I am not referring to the cracking effort (which can be tuned light or hard as wanted also with the older poppet and lever), I mean what happens AFTER the valve cracks open. With the S-wing poppet and curly lever, the progression between no flow and high flow is much easier, in practice the reg starts behaving like a G250 with its venturi-assisted breathing.
This possibly results in a much lower value of the WOB (Work of Breathing), but I do not have the proper equipment for measuring the area of the cycle.
So, while in the past also I did not notice a significant improvement going from unbalanced to balanced, with the latest poppet and lever, instead, the improvement is really relevant, and highly recommendable.
The cost is also quite minimal, or at least this is what I paid in February. Later it appears that Scubapro revised the price list for their parts, you should ask @buddhasummer or @axxel57 for the actual cost.
However, I also did find these parts from sellers here in Italy, in Germany and in Austria, at very reasonable costs on Ebay.

 

[Kupu]

Photo description of 109 to BA upgrade parts.
Replace duro poppet assembly shown at top with s-wing poppet assembly shown on bottom. Recommended not to throw old assembly in trash, it has value. Keep it, give it to helpful SB DIY friends, or sell it for a few bucks are better options.
New style curly foot lever is shown below s-wing poppet, but not always needed for upgrade.

 

[rhwestfall]

Duro poppet is valuable to retain!

 

[lexvil]

Duro poppet is valuable to retain!

and the spring and pad

 

[Bob DBF]

Just food for thought; if you have it on a balanced 1st stage, there is little benefit to the BA conversion.

I have 109's both balanced and unbalanced, never noticed any difference on a balanced 1st. Granted I've never picky if a reg gives me air, but I do like how a 109 breathes, and I don't own a working Scubapro first.

 

[jale]

Photo description of 109 to BA upgrade parts.
Replace duro poppet assembly shown at top with s-wing poppet assembly shown on bottom. Recommended not to throw old assembly in trash, it has value. Keep it, give it to helpful SB DIY friends, or sell it for a few bucks are better options.
New style curly foot lever is shown below s-wing poppet, but not always needed for upgrade.
View attachment 608019

Thanks a lot for the pic. Really clear

 

[halocline]

I find a difference in feel between the balanced and unbalanced poppet. It's subtle but noticeable. I think the balanced poppet is a little more stable and smooth. The big difference is in how long the regs hold a tune. Part of that might be simply due to the fact that the new spring is actually new. I've found that replacing the spring even when I buy a used balanced reg like the G250 makes a big difference. Those spring wear out over time and lose consistency.

 

[Angelo Farina]

I did always explain the better stability of the balanced with the fact that the spring has a much lower elastic constant, hence the static force keeping the seat pressed against the orifice is smaller.
Regarding the behaviour of the reg, I find absolutely no difference in the cracking effort. That is just matter of tuning (how much the orifice is screwed in). The difference I feel is AFTER the valve opens, the balanced requires less suction for the same air flow (or gives more air flow for the same suction).
However, not all of my 109s converted to BA behave the same in this sense. Some of them are really fantastic, they have a strong Venturi effect, and they breath exactly as a G250.
Some other units, despite being tuned to the very same cracking pressure, tend to give less air, and I use them as secondary (mounting orange mouthpiece and exhaust tie).
These hand-brazed brass devices are never identical each other, regarding the Venturi effect... And those with worst Venturi assistance are the ones where converting to balanced gives a more evident benefit.

 

[halocline]

Regarding the behaviour of the reg, I find absolutely no difference in the cracking effort. That is just matter of tuning (how much the orifice is screwed in). The difference I feel is AFTER the valve opens, the balanced requires less suction for the same air flow (or gives more air flow for the same suction).

What you are describing is caused by the drop in IP during inhalation. In a balanced 2nd stage, IP is providing the lion's share of the upstream force against the poppet opening. When this drops during inhalation, so does the upstream force, allowing the valve to stay open with less opposing force.