Diving Suunto D4 in 50% RGBM ?

[Divealpha]

I've seen on different forums that Suunto computers are fairly restrictive compared to other brands. My regular buddy(wife) and me are going on a liveboard in the Red sea in March, and have heard that the Diveops grounds you on the boat if your computer fails....
Setting the RGBM to 50% instead of 100% may give us a little more to go on, compared to many of the other divers we will dive with, who uses Oceanics, Liquision, and other brands.
The main reason I'm asking, is that we both have experienced:
Both D4's went in Gauge mode, my 3rd dive, buddy's 1st that day(Suunto support says we both must have started the dives in Free mode).
I'm sure mine was in Divemode, because I look at it a lot, escpecially when descending...

When the computers went in Gauge mode, one had one dive less during the last 24 hrs...
Asked the DiveOp if we could use tables for the rest of the trip, since both computers locked for 48hrs..
He proposed renting computers for the remaining 2 days, but dive in Air mode the next dive(since we dived Nitrox before) to be a bit on the safe side.
I know we should have a 12 hour break going by the book, but it was the last dive this day, and we then got almost 12 hours before the next dive.

I've heard that DM's in Egypt won't be that forgiving, so that's why I'm asking for advice or input on what to do.
The only other alternative would be buying a backup computer........
Changed batteries prior to last liveaboard, so that's not the issue(and got a pressure check as well from the local distributor)
A year ago, batteries went out once on both on same dive(70 dives on one, 50 on the other one), but that could be a coincidence...

I'm a bit concerned about loosing dives on this trip......

 

[Dive Bug Bit Me]

The main reason I'm asking, is that we both have experienced:
Both D4's went in Gauge mode, my 3rd dive, buddy's 1st that day(Suunto support says we both must have started the dives in Free mode).
I'm sure mine was in Divemode, because I look at it a lot, escpecially when descending...

When the computers went in Gauge mode, one had one dive less during the last 24 hrs...
Asked the DiveOp if we could use tables for the rest of the trip, since both computers locked for 48hrs..
He proposed renting computers for the remaining 2 days, but dive in Air mode the next dive(since we dived Nitrox before) to be a bit on the safe side.

If I get this right, you and your buddy went on a dive with the computer properly set up (cause you watched it on the way down), put the computer into deco (per its algorithm) then ignored that on an ascent getting locked out for 48 hours. But heck, no worry you just rent another computer and set it conservative for the next dive. (or both computers coincidentally had identical problems on the same dive)

Here are some thoughts:
- Get a VR NHeO computer. You can do 30 mins at 130 ft (40m) and shoot to the surface. It will flash some warnings, but will not lock you out. Admittedly the profile might give you a case of being dead, the computer however will function perfectly on the next dive.
- You could pay attention to your computer and when it says your remaining no deco time is zero, your dive is over.
- If you pay attention to the computer when you ascend, you can avoid getting locked out by stopping where it indicates. This assumes you have planned your breathing gas correctly. Don't rely on this until you are trained in deco planning. Also do not rely on your computer's time to surface function because it assumes a perfect profile. You are going to surface slower than indicated.
- Basically what I am saying is that if you are going to dive with a computer and ignore it because those around you are on more aggressive profiles then why bother with taking a computer along?

- From the little I know about RGBM it is more sensitive to reverse profiles and saw tooth profiles. This could be impacting your no deco limits.
- I would also guess that RGBM threw a deep stop at you which you missed (easily done).

In answer to your question of setting the computer to a 50% Reduced Gradient Bubble Model, I don't know. You have a decent computer so I would use the dive planning function to see what NDL time the computer allows at say 60ft (20m). Change the algorithm and conservatism settings and look at the revised NDL.

 

[Divealpha]

Wow!
Day one two dives 28meters 45min on 21%/Air
dive 3 27m 41min 30% Nitrox
div4 11m 32min 21% AIR 19:30
Sleep

day 2 07:09 28meters 40min 32%
dive 2 10:32 27m , 32% and the computer went in Gauge mode after 10minutes.

My buddydid only dive the second dive day 2, same depth, and it also went in Gauge mode........My D4 is from 2007, buddys from 2010.
I was prepared to us PADI tables to plan the next dive, based on the log, for the next dive, or spend the next ours on deck, but the DiveOp suggested using the rental in Airmode using Nitrox ...

We have been lucky enough to dive with far more experienced divers(even tech instructors) , who dives with D9, who sometimes could not figure out our computers behavior...
Suunto support says we both must have dived in freedive mode... I don't agree, but may give in, since I was the one who set the Oxygen percent in both computers...

We are not experienced divers (82-100), but have dived several places in both cold & warm water in Europe, and Asia, so please correct me !
Maybe I should mention that most of the dives where in strong currents, but the dive with the computerfailure was one of the better ones.

 

[DiveNav]

.....Day one two dives 28meters 45min on 21%/Air.

IF those dives were square profiles you should be dead

​

So, I assume they were multilevel dives. But, what profile? That is what really matter!

Send over the profiles so we can analyze them.

Alberto (aka eDiver)

 

[Foxfish]

I use the Suunto D4 and have also had this happen on the second dive of the day. I accidentally put it into freediving mode. It gave me a bit of a scare because the second dive went out to around 50 minutes with a maximum depth of over twenty metres. The first dive was similar abut slightly shorter. Computer locked me out for 48 hours. I presume that it assumes you died having freedived for over ten minutes. It is the only hassle I've had with the D4. Have to remember when putting on gear to check the computer is in the right mode.

 

[Divealpha]

Here are the two dives:



Diver 2 had the first dive with dive 2.

 

[DiveNav]

Here are the two dives:.....

Thank you.
Can you send me the actual logs? ediver-at-divenav-dot-com

Alberto (aka eDiver)

 

[Bubbletrubble]

I'm confused. Gauge Mode ≠ Mode the computer enters when a diver surfaces with a deco obligation.
I've never had a Suunto computer "automatically" switch dive modes from Air or Nitrox to Gauge.

Suunto computers will "lock out" in permanent Error mode for 48 hours if a diver surfaces with an unfulfilled deco obligation and fails to descend below the deco ceiling within a given time frame (3 minutes).

FWIW, the repetitive dive series that you described does not sound aggressive at all. It would be appropriate to try to rule out computer malfunction. However, the chances of two computers failing in a similar way on the same repetitive dive series points to operator error.

Have you read the manual for your dive computer? I only ask because very few people read the manuals nowadays.

Setting the proprietary Suunto-modified RGBM to 50% (vs. 100%) will give you greater NDLs on many dive profiles.
Before changing the RGBM setting to 50%, though, you should understand how this alters the kind of DCI "protection" provided by the RGBM algorithm. At least then you'd be making an informed decision.

For dive vacations where I want to minimize the chance of missing a dive due to computer failure, I'll bring along a backup computer. I purchased a used Suunto Vyper for $100 on Ebay. Perhaps you could pick up a relatively inexpensive backup computer for your upcoming trip.

 

[Mr Carcharodon]

Checking that you understand your computer settings with another experienced D4 user would be a first step. Can someone at your dive store help with that? If your computers are really spontaneously changing modes, and losing dives, I would try talking to your local dive shop and see what they can do to replace the units. Personally I have found Suunto to be entirely unresponsive to e-mail requests for support. If you have a significant trip coming up why not just buy a different computer?

The plots were pretty low resolution but it looks like the dives would not have worked on tables, and would be marginally OK at best with a computer. Out of curiosity how did you plan that? If you have a consistent way to do the plan in gauge mode that is one way to go. If you do not have a way to plan I would recommend aborting the dive, or keeping it to 10-15 m max depth. Even then you need a way to track depth and time and if your computer is doing odd things I would not trust it.

 

[Crowley]

I have been using a Suunto Vyper for almost 7 years, and my average day is 3 dives per day, maximum depth of the first dive 30m, I almost always have my computer set in air mode, despite the fact that I am diving nitrox, and I can easily work 10-12 days consecutive diving - as do most of the guides here in the Red Sea.

With this in mind, I would like to make the following points
- the Suunto computers are yes, more conservative than other brands (for example anything from Uwatec) but I would put them on a similar footing to Oceanic, and the Mares RGM model gives you less time than the Suunto computers
- Most of the recreational diving we do here should accommodate a 3 or 4 dive day on air without even coming close to deco. One exception is the wreck of the Thistlegorm, where air divers can easily head into deco if they are not careful, however with 32% nitrox it's next to impossible to reach that limit, assuming you dive the wreck "correctly"
- Suunto computers do not switch modes during dives, nor is it possible to change modes manually during a dive, so if a dive ended in Gauge mode, it means it was set in gauge mode, not dive mode, at the start of the dive.
- computers don't go into gauge mode if you violate a decompression obligation - they simply stop working. There would be no point to manufacturing a dive computer otherwise.
- computers do occasionally have software issues and if it is indeed randomly changing modes, then it needs replacing. Suunto have an excellent returns policy and usually dish out a replacement free of charge. It would be highly unlikely for two computers to do this at the same time, however.
- Dive guides in Egypt (and in many other locations, actually) will indeed ground you if you do not fulfill a decompression obligation. I have even done this to somebody who was diving nitrox and forgot to set his computer and left it in air mode. His computer went so far into deco it locked him out, but even though he was on nitrox, we have no way of knowing his decompression profile, and therefore we could not allow him to dive. I blogged about it after it happened.
- If you have accurate profile information and can re-calculated your dive using tables, then I would quite happily allow a diver to continue diving based upon the tables. This is often impossible though, because a typical first dive for me has a maximum depth of 30m, with a gradual ascent to the safety stop, and lasts for 60 minutes. Doesn't put my computer even close to deco, but is waaaaay off the limits of the tables.
- Suunto computers may err on the side of caution, but (At least for recreational diving) I would never suggest that somebody should buy an Uwatec (or whatever) simply because it allows longer time until reaching deco - recreational divers should not be pushing either limit, in my opinion and I am not going to argue with companies that have invested 30+ years and millions of dollars into researching their decompression algorithms!

Please everybody - read the manual and learn how to use your computers, because I get sooooo many divers who don't, and they are a valuable piece of safety equipment, not toys.

I'll shut up now!

Safe diving,

C.