R190 air delivery and exhalation effort

[ericpitar]

Greetings all,

I've just tested my newly serviced R190 in open water and found there's a bit too much air delivery. I had it adjusted and tested it on the pool but found it now has a tiny bit too much "inhalation" resistance but the exhalation effort significantly increased.

Question: Is there a tradeoff between air delivery and exhalation effort? that is, if I had too much air delivery but perfect exhalation effort initially and want to adjust to lessen the air delivery, would I inevitably pay with higher exhalation effort?


Thanks all.

e

 

[redacted]

Inhalation effort and exhalation effort are unrelated. If you do not have a freeflow problem, then inhalation (cracking pressure) really can't be too easy. But some divers are not comfortable with the feeling of positive pressure breathing (as if air is being forced into your mouth). You should be able to control this a bit using the viva adjustment to "block" some ogf the air flow into your mouth. If that does not work, you might talk to your tech about the problem. The housing has two opening that allow air into the reg. One is normally plugged (depending on which side the hose is connected). The tech may be able to change the air flow characteristics inside the case by removing or changing the plug. When I started DIY, I noticed my R190 has both plugs removed. I suspect that may reduce the positive pressure breathing sensation but I've never played with it to see for sure. Hopefully DAAquamaster will be along and help.

As far as the high exhalation effort, that should not be unless the exhaust valve is too heavy or sticking to the sealing surface. It is not adjustable. Talk to your tech about this problem and see what he can do. See if he replaced the exhaust valve. Hopefully no one lubed the seating surfaces which might cause the valve to stick.

 

[halocline]

Sorry, I have no idea what you're talking about. Exhalation effort is governed only by the exhaust valve. I also don't understand your comment "too much air delivery" although I suppose you could be talking about a pronounced venturi effect. Try turning the VIVA to min and see if that changes it.

Adjusting the the inhalation or "cracking effort" is a simple process. On mine, I adjust it for about 1.5" of water (a guess, I use a bowl of water to test it) basically just enough so it doesn't freeflow.

Edit: Whoops, AWAP beat me to it.

 

[ericpitar]

Additional info......The tech changed the IP from 145 to 140. Also, this R190 is actually an octo and now that you mentioned about the "plug", I recall somebody (perhaps DA Aqua) mentioning a difference in the "plug(s)" between an octo and non-octo R190. Are we on to something here?

Meanwhile, the R295 that was my primary-turned-octo no breathes better than the R190 so I might actually promote the R295 back to its primary 2nd stage status.

 

[redacted]

DA was probably referring to the large plug that goes in the case opposite the LP hose connection. I'm referring to smaller housing plug which blocks one of the two openings in the housing which contains the poppet assembly and spring.

 

[Hoosier]

DA was probably referring to the large plug that goes in the case opposite the LP hose connection. I'm referring to smaller housing plug which blocks one of the two openings in the housing which contains the poppet assembly and spring.

Which side do you used to block, either mouthpiece side or other side?

As you know, there is a different on air exhaust (flow) when you push a purge button...

 

[DA Aquamaster]

There are two holes in the poppet assembly and in the good old day, both were open. The plugs cam along to plug one of them to increase free flow resistance to meet EU standards. The plug normally goes in the aspirator hole that points away from the mouthpiece.

Personally, if I owned an R190, I'd take the plug out.

The VIVA flow vane works well to reduce the positive pressure effect when breathing from the reg. My thoughts are that an R190 should be adjusted for minimum inhalation effort of 1.2" of water.

 

[ericpitar]

My thoughts are that an R190 should be adjusted for minimum inhalation effort of 1.2" of water.

What exactly do I tell the technician? "Please adjust for minimum inhalation effort of 1.2" of water"?

Can someone describe how he would do this? I don't want him telling me he "did it" by turning a little screw if there's something else involved in doing this.

 

[ericpitar]

Recall the air was a tad too much at 145 and now quite stingy at 140.

Would it likely remedy or lessen the problem if I had the tech set the IP to something like 143 which would be around halfway between the initial 145 and 140?

Or would unplugging the hole on the poppet assembly be more effective?


er

 

[DA Aquamaster]

It depends what you have the R190 on.

If the first stage is unbalanced (a Mk 2) the IP will drop about 20 psi from a tank pressure opf 3300 psi to 300 psi. In that case, you want the IP at or very close to 145 psi at 3300 psi tank pressure to ensurer it is still a healthy 125 psi at low tank pressure.

Another issue with an unbalanced first and second stage combination is that you want to adjust the second stage for minmum inhalation effort at the highest IP it will encounter. If you adjust it to a low inhalation effort at a low or midrange tank pressue, it will freeflow slightly at high tank pressures.

If the first stage is balanced the IP will be stable. How stable depends on the design. The older Mk 5 and MK 10 would vary about 4-6 psi while the Mk 20, MK 27, Mk 17, etc, will not vary at all. In that case, you can adjust the second stage inhalation effort at any supply pressure and not worry about it.

On some piston first stages (like the Mk 2, Mk 3, Mk 5, Mk 10, Mk 15, Mk 20) IP adjustment is done in 5 psi steps with shims so adjustment from 145 to 143 psi is not really possible (or really needed either). On a diaphragm design with a sporing adjustment pad or with the Mk 25 with the adjustable seat retainer, precise IP adjustment can be achieved. But again a less than 5 psi change in IP makes no difference in how a first stage performs, what matters is the second stage adjustment.

On the R190. the inhalation effort is primarily adjusted by turing the orifice in or out slightly, although in some cases, it may be neccesary to readjust the nut securing the lever on the poppet assembly. In a few cases, it may require a new spring if the old one is too stiff to get the inhalation effort down to the minimum spec.

The biggest potential problem with a dual adjustment second stage like the R190 can occur when increasing the inhalation effort. As the orifice is turned in to increase inhaltion effort, it increases the play in the lever, if the play in the lever is excessive, the dipahragm can no longer fully open the valve and a greatly reduced air delivery will result from the restricted working range of the valve. If the lever is properly adjusted, the reg should begin delivering air with only a slight depression of the purge button. If it requires more depression than normal to get the reg to purge, it should be taken in to be readjusted.