I want to publicly acknowledge how right @Superlyte27 was/is.
I've been diving a rEvo for 4 years. I was happy with it. I still am! But, I knew from about Day 2 that it does not breathe all that great if you are in perfectly flat trim. I almost gave up on diving a CCR at all after my first day in open water during my MOD1 class on rEvo. I was swimming around doing my best to stay totally flat. I went to bail out several times during that dive, just to catch my breath. To be fair, conditions were a bit rough that day with a lot of surge on the bottom on Molasses Reef. Then I figured out that if I just swam just a little bit head up, the breathing was fine. And that has carried me through my 4 years on the rEvo.
Last month (December), I went to cave diver school and got cave trained and certified on OC then did a crossover to CCR Cave on my rEvo. The rEvo diving culminated in a long dive in Ginnie Springs. The Ginnie dive was my longest dive I've ever done, at 170 minutes. It would have been longer, but after about 130 minutes, swimming into the current and doing my best to stay in perfectly flat trim, I had to give up. The work of breathing had brought me to the point of getting the chokes. I turned the dive before we got to where we were trying to go. I was confident that if I continued any further, I was going to have a serious emergency. As it was, we turned and mostly just drifted to let the current carry us out, but I still switched to BO for about a minute at one point, just to let my airway relax and recover a bit. I went back on the loop and was fine for the rest of the exit. But, that dive showed me my limitations when it comes to diving a rEvo in a cave.
2 days later, my friend said he was opening a Dive Rite account for our shop and ordering a Choptima for himself. I jumped right in on that and ordered one, too. I don't want to dive caves on OC. And I don't really want to dive them on my rEvo, either.
Last week, we went down to DR HQ, took delivery of our new units, and did the crossover training to get certified on our new units. Then we went cave diving.
Our last dive of the trip was back to Ginnie. This time, I did a 233 minute dive and never once felt out of breath. And that is the real summation of my Choptima testimonial.
I've been reading @Superlyte27's slander (lol) of the rEvo for years now, but basically had no experience to really understand how accurate (or not) he was being. It was the only unit I had any time on. Now, I get it. I feel like the rEvo does not breathe as poorly as he makes it sound - in an all-purpose diving context. In a pure cave diving context, well, I pretty much agree with him. I only have a bit over 11 hours on the Choptima, so far, but now that I have it, I can't see ever taking my rEvo into a cave again.
Don't get me wrong, though. I still love my rEvo and will continue to use it for just about any other diving that I can think of - except maybe diving where I fly and it's more or less recreational stuff. Then I would pack the Choptima and use it with my single tank OC rig.
The Choptima is certainly not the be-all, end-all CCR (for me). I've been diving it with a Katana 2 sidemount rig and it was great in the caves. But, there are some things about it that are reasons why my rEvo will still get used for my non-cave diving. They include:
- I do like a clean, uncluttered chest and the Chop is the opposite of that.
- I do not care for diving sidemount off an ocean boat. So, to use the Chop, I would be diving it with back mounted doubles. I would much rather have a rEvo on my back and sling BO bottles on my sides than dive with a Chop on my front and double steel tanks on my back.
- I do not like that the Chop has (and needs) an inline shutoff on the dil input. With it shut off, I can't get any dil into the loop via ADV or manual add. I would prefer it to have a manual add that I can use at any time, and an ADV that worked where I could pull air through it when I want, but not pull air through it when I don't want. (which is how my rEvo ADV works).
- The Chop ADV and dil manual add are the same device - basically a device like a drysuit inflation valve that is mounted on the left side of the unit. Thus why you cannot have one on and the other off. They are the same thing. You can suck against it to pull dil via the ADV or you can press on it to add dil manually. What took me a couple of days of diving to figure out is that that valve adds dil to the loop MUCH more slowly than the rEvo ADV and MAV do.
In 2 different dives during my crossover, I ended up switching to bail out. Both times it was because I felt like I couldn't get a breath. I would think "I can't get a breath, I need to add some dil to the loop." I would add dil and still not be able to get a breath. So then I would think "did I add too much? Is the loop full now and that's why I can't get a breath?" So then I would try venting some gas from the loop and still not be able to get a breath.
It turned out that both times the problem was simply that the loop volume was too low and when I manually added I was not adding enough, because of how slowly it adds. I was/am used to the rEvo where manually adding or pulling through the ADV, either way, results in a lot of gas very quickly. So, what felt like a long time of holding down the Chop manual add simply was not nearly long enough. Once I figured that out, I didn't have any more trouble with breathing on the Chop.
I do not like how that works. Further, we were told numerous times in training that, if we were ever going to do hot drops in the ocean, we would want to change the dil connection from a LP inflator connect to a QC6. Otherwise, the dil valve would not be able to keep up with the volume requirement of a deep, fast descent. Apparently, part of that is because the Chop dil reg is setup for an IP of about 85 psi, versus a more normal 140 psi or so on the rEvo dil reg.
I don't like how it works, but I don't dislike it so much that I wouldn't dive it. Now that I understand it, I can work with it just fine for cave diving, or even for recreational-ish ocean diving.
- I am not thrilled that I cannot reach my power inflator for my wing with my right hand when I have the Chop clipped on. When diving my rEvo, I often use either hand for adding gas to my wing or adding O2 or dil to my loop. With the Chop, adding dil or wing gas is a left hand-only affair. And, if I have a light on the back of my left hand, I can't use it to reach my drysuit inflator, either.
- I feel like the breathing loop hoses are too short for me. I kept saying all during my class that whenever I was simply in horizontal trim and looking straight ahead, it felt like the loop hoses were trying to pull the DSV out of my mouth. I adjusted the Chop repeatedly to let it ride higher and higher up on my chest, but nothing I did fixed it. It came with 12" hoses, but they also offer 15" ones. I have a set of those on the way to try.
- I like the rEvo Monitoring System. It lets me use my sorb very efficiently. And it gives me confidence that I am not in imminent danger of breakthrough. I rarely throw away any significant amount of unused sorb. Now, I will likely be throwing out an hour (or more) worth of unused sorb on a somewhat regular basis. I do wish the Chop had something like rEvo's rMS.
- I got my Chop with a NERD 2 controller. It uses the Divesoft mounting system to attach it to the DSV. I wish it held the NERD lower. I bent the bracket to get the NERD as low as I could but it is still higher in my field of view than I would like - i.e. higher than the NERD on my rEvo. But, it is really nice that it holds the NERD solidly and doesn't let it shift around on the DSV like the rEvo mount allows.
Other notes:
We were diving during class using EAC cartridges. For the 2 days after class, I packed the scrubber using Sofnolime 8-12. My very subjective sense was/is that using loose sorb resulted in easier breathing than I had with a cartridge. John only dived the last day with loose sorb, but he said that he felt like it breathed WAY better with loose sorb than with a cartridge. I'm getting a 4-pack of cartridges to have on hand for "just in case", but I will have loose sorb on hand anyway, for use with my rEvo, so I expect to continue to use loose sorb in the Chop, too, as my SOP.
The Chop is definitely more complicated to assemble and to breakdown for post-dive maintenance than my rEvo. Not hugely so. But, there are just more pieces/parts to take apart and put back together as part of the normal routine.
The chop is fully electronic where the rEvo is a hybrid, which has a Constant Mass Flow orifice to continuously feed O2 into the loop. What I noticed is that the Chop solenoid fires a LOT more often. When swimming on low set point and maintaining a higher pO2 manually, I had to manually add O2 a LOT more often. But, it also seemed that the solenoid fired shorter bursts of a lower volume. Running with the solenoid on the Chop seemed like it had less of an effect on my buoyancy than diving the rEvo and letting its solenoid manage the loop's pO2.
I am really looking forward to getting more cave experience diving the Chop - and continuing to dive in the ocean with my rEvo. Tools for different purposes and I love 'em both!
TL;DR
Skimmed through all that and have 2 points.
The chest clutter is real and definitely takes a while to get used to. The tradeoff is the ability to don/doff in water and access to everything on the unit for trouble shooting. Don/doff has been useful for me when diving off of a small rib with a full tech load.
2nd, I am not a fan of the ADV or the shutoff. I removed both and replaced with the DR MAV (I took the O2 shutoff off too)
