My new G250Vs and ramblings

[rsingler]

Happy new year!

I still have a hard time understanding how the venturi intensity can be related to a different spring tension, if the spring/lever assembly can be adjusted to the same cracking pressure? Then the venturi effect should be about case geometry overcoming spring force to depress the lever. It seems regs with slightly elevated cracking effort will still freeflow on max viva, so I am not sure I fully understand...

I agree with you. That's why I asked about the curly foot levers. It seems like width of valve opening should be the only factor maintaining Venturi-induced flow unless cracking effort was significantly higher.
There is one other possibility - that the curve of dynamic increase in spring resistance (i.e., stiffness) is much higher with the 215. But as @Open Ocean Diver has noted, I don't see much difference between the springs. The 215 was first introduced with the C300 to decrease friction with its coating, I believe. Otherwise, I thought their performance was identical.

 

[Couv]

This (known as spring rate) is probably the answer:

There is one other possibility - that the curve of dynamic increase in spring resistance (i.e., stiffness) is much higher with the 218.

But let's back up to this statement I skipped over on first reading:

Swapped out .218 with a .216 on primary, did nothing else,

@buddhasummer Was the cracking effort exactly the same after swapping out the springs? If lower, was it still within specs?

You see, the problem with convicting a part (in this case the spring) is Simon does not have a known good G250V to place the "suspect" spring into and duplicate the problem.

 

[Couv]

spring lowers Venturi effect, but why did they bother?

Not exactly; the Venturi effect is not altered by the force of the spring*-it's a question of whether the Venturi effect is strong enough to override the closing force of the entire demand valve.

*If the springs were different shapes/sizes and in the air path, yes they could in theory affect the laminar flow; but I think we would be splitting hairs with the two example springs.

 

[Open Ocean Diver]

it's a question of whether the Venturi effect is strong enough to override the closing force of the entire demand valve.

My experience with my 108HP would agree with your analyses, the 218 spring is stiffer dynamically compared to the 216 as @rsingler said.

 

[buddhasummer]

Im afraid my understanding of the physics involved is way beyond my brain all I know is after swapping spring to .216 on my 2 G250Vs they both violently free flowed. To me logic indicated the spring as the cause as I did nothing else. Happy to try other things if anyone has suggestions. I think the cracking was slightly lower with the .216 but not significantly.

 

[buddhasummer]

Just seems too coincidental. I'll try with more springs I guess to see if it's consistently repeatable. Happy to send someone .218 springs for them to try.?

 

[halocline]

Simon, try increasing the IP to the maximum allowed (maybe 145 or so) and see if it free flows with the .218 spring.

 

[buddhasummer]

Simon, try increasing the IP to the maximum allowed (maybe 145 or so) and see if it free flows with the .218 spring.

Thanks, Matt, currently it's at 135. I'll try that later today. Although my spring swap did solve the "issue" it does seem strange to me but given it did with no other changes made I just decided that it was the spring.

 

[buddhasummer]

Got a full tank of air, I'll try to be as methodical as possible, but will do 5x spring swap on each G250V this should give a better sample to gauge results from. I'll use 5 of each spring on each.

 

[Open Ocean Diver]

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