Optima ADV Adjustment

Drmike

min loop means you have enough volume for a full breath no more and no less.

so i would assume if your adv is firing at the end of inhale that suggests either you either have too little volume or the optima adv is way too light..from what Marc is saying perhaps its the latter. Cant this be fixed?

FWIW I found diving too close to min loop is not always a good idea from a wob and good lung ventilation perspective.

Min loop + works better for me

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jiseson

i have enuff vol for just one breath, my adv is detuned-by mark of dre! if i leave adv on it WILL add dil! so i shut it off and breath happily the min. loop vol. .in addition, by having it off i am able to realize when my PO2 is dropping by bouyancy change. not sure what u are not getting

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Drmike

really? my post apears quite straight forward to me, but to clarify;

Sounds to me like the adv is far too sensitive.

Re: detecting ppo2 drop via bouyancy change; what degree of ppo2 drop are you able to detect?? I would assume the loop vol change/0.1bar PPO2 wouldnt be very much at all (especially when deep) and easily masked by small changes in depth (especially when shallow)

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Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

n2diving

The O2ptima ADV, as delivered from the factory is indeed far too sensitive for nearly all divers. This is deliberate decision on their part, for safety reasons. For the O2ptima ADV, which is located in the breathing loop in front of the inhalation counter lung, a sharp forceful inhale will trigger it to release some gas into the loop even if the CL's do not bottom out. Thus, leaving it on during the dive will make attaining and maintaining an ideal loop volume difficult for some divers. A properly weighted diver who instinctively takes an abnormally deep breath right before descent will sometimes have difficulty starting their descent as the O2ptima CL's, when over full, can add an enourmous amount of lift that must be overcome. We teach to leave the O2ptima ADV on for the descent, and immediately turn it off once on the bottom.

Instructors usually assist the student in adjusting the O2ptima ADV to be a bit more stiff, and the simple proceedure is also clearly described in the O2ptima manaul, but I suspect most of us don't really crank it down on students as much as we would do for ourselves.

Like most any reg, it also performs better in some orientations than others and does not perform as well when the diver is inverted, so that has to be kept in mind when adjusting for our area since inverted rapid descents are common here. Detuning it enough to make it right for a slow head's up descent will make the diver work hard to get a breath on a rapid inverted descent. Under some circumstances, some divers including myself, prefer to use the manual addition valve to manage the CL volume on some types descents. The O2ptima design provides the benefit of making this very easy to accomplish those who choose to manage CL volume manually.

All that being said, Marc is a special case and there are issues for him with ADV's on two different CCR designs which are not fully understood. Marc has an exceptionally large lung volume, but I also suspect a very forceful inhalation as well.

Drmike

perhaps it should be...once the adv lightness issue is fixed and users dont have to shut it off

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

Drmike

thanks for the details.

My thinking for a good adv is it should be tuned so that it can be left on all the time and still run min loop vol. This I feel is safer than people shutting off their advs. I know some designs make that harder but many apear to achieve it.

Id suggest an adv thats tighter but able to be left on all the time is safer than one thats light - and so turned off

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Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

LEDiveVideo

I agree with Mark that this thread has deviated from the original intent, and that the ADV open or closed would have had little bearing on the accident.

Although Mark's buddy, I dive my ADV differently than he does. As he indicated, the ADV can be adjusted so that it takes a somewhat strong inhale to activate. This is how I have mine set. Unlike Mark, I descend with my ADV turned on, and this works very well for me. Once at depth, I turn it off, simply because I don't need it anymore. As Mark stated, an Optima diver is trained to do a dil flush with the manual add button, not with the ADV. On occasion where I have forgotten to turn it off, and am letting the solenoid manage the PO2, my ADV is not so sensitive that it is adding dil unnecessarily. However, if I am manually managing my PO2, I want to detect the drop in minimum loop volume without the ADV kicking in. It might or it might not, the point is I don't want it to, so I turn it off. I'm not trying to disagree with how others manage their ADV, as I said, Mark does not dive his the same as I do. I'm simply pointing out how I dive it, and that this works quite well for me.

Also, this is not unusual to the Optima. Mark and I were recently in the Red Sea to be trained on the Sentinel, and after the first couple of training dives were told that we could turn the ADV off once we reached depth, and most of us in my group did so from then on.

silent running

I agree with this.

In my experience, having an ADV that needs to be shut off would be at best not desirable and at worst, dangerous. Having to spend even .5 of second fiddling with a shut-off to get fresh gas negates the advantage of an ADV in dealing "automatically", meaning fastest and hands free, with an emergency such as the onset of a CO2 hit or being caught in a sudden down welling. If it has to have a shut off, it's not really an "automatic" DV anymore is it?

Genesis

Ok, I don't get it.

What's so difficult about hitting the manual add?

I don't have an ADV on my (homebuilt) unit. An intentional decision (one less thing to break or screw up on you, or for you to screw up)

So far I've not seen an issue. I can manual add fast enough to keep up with a quick descent, and I can manual-add fast enough to keep up with a moderate inhalation pace starting from "exhale all loop volume through nose".

So where's the problem? I understand the convenience of an ADV, but not the necessity. And one that fires when the loop is not bottomed out just begs for it to be disabled, in which case you don't have one at all.

When in need of a breath on bottomed out CLs, do you want one potential reaction to that situation or two? With an ADV and shutoff, you have two. WIthout an ADV, you have one.

Pick.

And yes, I can easily detect a 0.2 PO2 drop by the CLs bottoming out on inhalation when running minimum volume; which I consider (another) safety feature. Since I can't get dil added except by explicit action its not possible if I start with minimum volume at constant depth for me to get to a hypoxic loop without bottoming out the CLs. (Yes, I "get it" that this "feature" is negated if I am ascending, of course, but this is a tertiary level of safety; every bit helps!)

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diverreb

Another reason for shutting off the ADV on an O2ptima is it fires in certain body positions. When I turn on my side, I believe its my right side, when looking in holes or under plates for Lobster and if I have to maintain that position while trying to get the Lobster, the ADV goes off. I believe it's the Hydrostatic pressure of the lung positions that cause it.

I don't know if that can be stopped by adjusting the ADV, but if I'm in hunting mode, I'll keep it off on bottom.

It is fairly sensitive, and I want it that way. I've heard people say the ADV won't dump quickly... The way mine is set it can blow up the lungs in second or two.... and flush very quickly, if necessary.

Richie