Importance of Tuning 1st stage with particular 2nd stage?

[Andrew Dawson]

Greetings,

I did search around but could not find a good, definitive answer.

I have 3 1st stages:

MK25
MK25
MK20UL [but upgraded with a newer swivel turret and MK25 guts]


...and 5 2nd stages:

G250HP
S600
S600
R380
G250 [being fixed]

These were all recently serviced with zero dives on any of them.

Some of the regs were serviced while coupled with a particular MK25, others were not.

I have never dove any of these particular regs [yes, lots of MK25s/S600 and R380s before but not these ones] would like to see which reg I like the best for my primary and for octos, etc.

So, here is the combos I want to make

MK25-A on a steel 120:
S600
S600

MK25-B on a 19cf Pony:
G250
G250HP

MK20UL on a 19cf Pony:
R380

Questions: When a 1st and 2nd stage reg goes in for service and is...."tuned"...how much of an effect is there when switching the 1st and 2nd stages around?

Also, for MK25s does having the 2nd stage on the bottom of the turret LP port improve air flow/supply? I read that having the 2nd stage on that LP port was for optimal air supply...but, I imagine that is practically immeasurable...here is a pic:

 

[Timmy V]

It should be negligible if the IP was set similar on the first stages. 135 +/- 10

And yes. Bottom port flows best but to the average person not noticeable.

 

[Timmy V]

The difference would be if you you tried an octo as a primary as they are set to a higher "breaking point"

 

[tbone1004]

the only one that will care is the R380. The rest of them are balanced and adjustable, you won't be able to tell

 

[Andrew Dawson]

Excellent, I forgot along the path...about Octos having the higher cracking force...to prevent free flows on the surface...which is why they were never great breathers!

Yeah, I am still getting back into things it seems

Great info, guys!

the only one that will care is the R380. The rest of them are balanced and adjustable, you won't be able to tell

Why would the R380 care which 1st stage it has?

 

[Timmy V]

The R380 will only care if the IP is out of whack between 1st stages.

 

[Andrew Dawson]

If the IP on two different MK25s were very much different [say 120psi on one and 170psi on the other]...would balanced 2nd stages be affected as far as breathing effort?

I see, so the R380 is more sensitive to different IP pressures as it is non-balanced? [just a downstream reg?]

 

[Timmy V]

The breathing (cracking effort) would not really be affected much but the air flow would be. And yes a downstream reg would freeflow at an increased IP.

 

[tbone1004]

Excellent, I forgot along the path...about Octos having the higher cracking force...to prevent free flows on the surface...which is why they were never great breathers!

Yeah, I am still getting back into things it seems

Great info, guys!



Why would the R380 care which 1st stage it has?

@Timmy V some octo's may be set to higher cracking efforts, but there is nothing that says they can't be tuned right to the edge. I also call BS on anyone being able to tell a difference in flow based on which port you are breathing out of. Heck, I'd be surprised if the machines can tell.

The R380 is the only unbalanced second stages which means if there is a decent change in IP, i.e. one is set to 135 and the other to 145, the cracking effort will change. If the regulator is set right at the edge on a regulator that is at 135psi, and the other one is 145psi, then it will freeflow. A couple psi doesn't really matter, but 5 or more will

 

[Timmy V]

@tbone1004 you're pretty much echoing what I said. A 2nd stage can be set to whatever you want it to be. Octo or not. That said a typical "shop tuned" octo will have a higher breaking point. As for the better flow out the bottom? I assure you a machine can tell as it's one less 90 degree turn vs side exit. You or I would not be able to tell.