OP
What’s the deal... SP 108 HP verses 156BA
- Thread starter Open Ocean Diver
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.218 springs, I have a bunch if anyone's looking to "upgrade" the .216.
OP
Do you have any for the 108hp?
- Messages
- 17,524
- Reaction score
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- Location
- Somewhere between here and there
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- 2500 - 4999
Without looking I'm not sure if it's the same part number and/or can be used. I'll check later unless someone answers first.
OP
Ok thanks maybe you can add to my existing order if it hasn’t shipped.
OP
How much for the 218?
halocline
Contributor
The 108 is not the same case as the 156 and is a completely different kind of valve. The 156 (aka balanced/adjustable) is the same case and valve type as the 109, aka adjustable; both have barrel poppet designs, same lever and diaphragm, while the 108 has a classic downstream valve/lever and a different diaphragm. (although I believe there were two different styles of 108 cases/diaphragms)
I'm not sure how you are taking these measurements, generally I don't put a lot of stock in WOB numbers, but one thing is that it is unlikely that the 108 would actually work with a .7" cracking effort. It would almost certainly freeflow in the water at any sort of depth due to case fault geometry.
I've used several of the 108s throughout the years on real dives, and some of them have performed very well, but IME they are not as stable as the 109/156. I believe that's why they were usually tuned a bit stiffer.
With regards to the spring, in the later models, SP used the same spring for the balanced s-wing poppet (like the G250) and classic downstream valve, (like the R109). It's just that the spring is much more tightly compressed in the downstream valve. I suspect that this is also true for the earlier 108 and balanced/adjustables, but I'm not 100% sure. It would be easy to look up part numbers. Maybe you guys already know about that.
A very knowledgeable SB member once posted that SP engineers would pick out the springs with the closest tolerances for use in the balanced poppets and use the remaining ones for the unbalanced downstream valves. So ordering that part number for replacement springs could be a little hit or miss. I never had a problem with any of the ones I put in balanced/adjustables.
I'm not sure how you are taking these measurements, generally I don't put a lot of stock in WOB numbers, but one thing is that it is unlikely that the 108 would actually work with a .7" cracking effort. It would almost certainly freeflow in the water at any sort of depth due to case fault geometry.
I've used several of the 108s throughout the years on real dives, and some of them have performed very well, but IME they are not as stable as the 109/156. I believe that's why they were usually tuned a bit stiffer.
With regards to the spring, in the later models, SP used the same spring for the balanced s-wing poppet (like the G250) and classic downstream valve, (like the R109). It's just that the spring is much more tightly compressed in the downstream valve. I suspect that this is also true for the earlier 108 and balanced/adjustables, but I'm not 100% sure. It would be easy to look up part numbers. Maybe you guys already know about that.
A very knowledgeable SB member once posted that SP engineers would pick out the springs with the closest tolerances for use in the balanced poppets and use the remaining ones for the unbalanced downstream valves. So ordering that part number for replacement springs could be a little hit or miss. I never had a problem with any of the ones I put in balanced/adjustables.
As mentioned by halocline, spring for 108HP is the 01-020-216.
OP
I have a flowmeter, vacuum pump and magnehelic gauge. I’ve only had the 108 in a 15 foot pool with no free flow, but to be honest I don’t remember what it was tuned to at the time.
How did your 108 at depth compare to your BA when it was working stable?
OP
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