Meg Course with Ted McCoy

[tbone1004]

How do you retune the cracking pressure on the ADV? Since it is a schrader valve with a built it spring you can't really alter the spring tension
I would suggest if your adv is not firing because it does not hit squarely against your chest then an adjustment of your counterlung or possibly taking the twist out of the breathing hose between the T-piece and the head will fix that.

Haven't taken it apart, but I adjusted the lung and t-pieces a couple times and every time I was diving min-loop it kept getting pushed off to the side since it was turned off. I'm sure if it was left on it would increase the lung volume a bit and stay put, but it just isn't something I want to mess with compared to going to the iBov that has the ADV built into the mouthpiece

 

[wedivebc]

I am not famiar with the iBOV but I've always liked the concept of a ADV in the BOV. SInce you will likely be scootering you may want to ensure you can isolate it if the water pressure may screw up your min loop volume in a hurry.
The meg is a very well designed unit and I caution my students not to be too quick to modify their unit in order to solve a problem that may not exist. I don't scooter in caves so I haven't experienced some of the problems you seem to be having with the ADV. If you are changing the BOV just to solve this problem there may be a simpler fix.

 

[tbone1004]

@wedivebc thanks for the insight. Thankfully on the iBov you have three modes on the dial, OC, ADV, Loop so you can dial it over to turn the ADV off if you don't want to put an inline shutoff on. Also looking at the Poseidon bov which uses the Xstream second stage and that won't fire when in the flow.

Switching to the bov is for some other reasons, but the iBov and Poseidon went to the top of the list because of the integrated ADV

 

[rjack321]

I made my own Meg checklist too, Leon and his lawyers would have a fit if we had done that in class however.

I agree on the cave vs "standard" dil flush. Unless my loop is crazy high I just exhale through my nose and let the ADV fire to drop my ppO2. But I have actually only done this once, scootering Clear Cut cave in the Tallahassee area that had a ton of ups and down (down to 102ft and up to about 3ft). But I am using the TOS lungs which are comparatively small, so scootering in someplace like Ginnie I tend to vent more on the ups than the average CCR diver. Which means I have re-add volume on the downs, which prevents ppO2 spikes unless then dip is really substantive.

My guess is that part of your issues was a too loose dump valve. They last a few years but scootering into flow with a loose one will create pressure on the CLs and force it to dump.