Suunto computers....

[DC53]

My Suunto Vyper Air seems absurdly conservative. At least that is the way it seems; I have never had any DCS. However, I wear a Veo 250 on my right wrist and a Suunto Vyper Air on the left (with tank transmitter). I pay more attention to the Suunto because it is supposed to be a better computer and it provides a lot of easily readable information.

However, even when both computers are set for the same nitrox, the difference in No Deco Time is HUGE. Today diving off Palm Beach, the Suunto had me with a few minutes of deco obligation when the Veo was still in double digits of No Deco time (15-19). And no, I was sure the nitrox percentage was set the same for both. Also, I was loosely diving with others who all stayed down longer on the same nitrox and their various computers did not show deco obligations. Now, I don't have a lot of DCS risk factors... Although I am 56 years old, I am slender with a low body fat percentage, in good shape, have never had a DCS incident.

What I would like is opinions as to whether my sense that Suuntos are conservative to a fault is true or not. And, if so, how much should I adjust the computer to a less conservative calcualation? Any opinions welcomed and are welcomed as opinions only with no obligation or liability for being accurate.

 

[Katamuki]

If you compare a given FO2 at a given depth for a given time in a square profile you will find that the Suunto calls "deco" one "box" of time limit before a printed NAUI table. This can shave a few minutes from a dive obviously. What so many new divers seem to do is treat a computer like an egg timer rather than a measuring device. It is NOT a good idea to chase NDL limits by going up a few feet to gain a few more minutes. Nitrogen saturation will continue to occur as you are not off-gassing as you continue acend slowly.

The Veo uses a set of tables that are very liberal as far as time. I have never done actual comparisons to their computations vs a printed table but I suspect they are no different than any DSAT/Oceanic/Hollis product. Whether their algorithm is too lenient is a matter of opinion but for me I would rather be safe than sorry. If you do ever develop a deco obligation this is where a huge difference between the two computers shows up. The Suunto will credit you with deep stops or 10ft stops or whatever you have been trained in and clear its time obligation for decompression. The Veo will top-load the time and despite whatever ascent schedule you run it will require you to hang at 10ft (I believe 10 is the level...) for the entire deco time.

If you run a deco plan on V-Planner and do the dive in Computer mode with a Vyper Air and a Veo while following the V-Plan you will find the Suunto clearing wihin 1 or 2 minutes of the total schedule and the Veo saving almost every minute for a 10ft stop. For the recored I own an Atom 2.0, VT3 and a Vyper Air.

Bottom line for me is that I understand how the Suunto tracks dives and this makes me confident in it but then I also use IDeco and V-Planner to generate slates.

 

[Jorgy]

Among dive computers Suunto's are known to be in the "most conservative" group....

As far as making it less conservative that is not possible, you can make it more conservative but not less......

http://www.scubadiving.com/files/old/images/pdf/200806_chambertest.pdf

14 New Computers | Scuba Diving Magazine

Hope this helps......M

 

[ickybingh]

Make sure it is set to A0/P0. This can make a pretty big difference in no deco times.

 

[DC53]

A couple of things..
"SUUNTO Vytec has the ability to set the RGBM model to 50% effect, thereby making the model less conservative. This is for "experienced divers who are less prone to decomression illnes and who are willing to accept a greater risk", according to the Vytec intstruction manual" Research of other relevant posts suggests this is a relatively small incremental difference in NDL, although the percentage difference seems to increase as the number of repetitive dives increases.

Before I got my Suunto Vyper Air, I used to rely on my Veo 250. I recall that during some Caribbean deeper dives or second dives I used to get pretty close to the NDL limits... Not right on them mind you, but with maybe 4-5 minutes left before starting up. (My SAC rates runs between .43 to .52 on most dives so I can get close to NDL well before running low on gas. I never got any DCS symptoms during those dives.

Now if were to use the VEO as my guide to NDL my Suunto would have me incurring a multiminute obligation. Another little item is that I was recently diving a long deep dive with a DM off the Florida coast. We dove side by side on the same Nitrox and my Suunto finally counted down to zero NDL and then gave me a ceiling depth. (My Veo said I had about 15 more minutes.) I pointed out the reading on the Suunto and indicated I was going up and he continued on at the same level.

So something is not right. Either the Veo is way off or the Suunto is way too conservative. The same results occur with different nitrox settings, by the way. Yesterday I dived with my wife and the Suunto NDL times got down to 2 minutes and I showed it to her and she showed me her VEO 180 which said 15 minutes and indeed it agreed with VEO 250 on my right wrist which said 16 minutes. On the boat she said "yo nuts about NDL's with that Suunto."

By the way does the Vyper AIR have AO/PO settings and how do they work.... I did read the manual cover to cover and don't recall that setting; perhaps I missed that.

 

[Katamuki]

My first bit of advice DC53 is that if your going to be extending your dive times like that you need to take a TechNitrox/Deco Theory class. This will shine a light on the issues you have raised.

When the Suunto sets a "ceiling" as a mandatory stop depending on the minutes involved this can clear with the normal safety stop you do at 20ft, 15ft or 10ft. This time will also be reduced by an ascent profile using 50% stops and subsequent mulit-level stops, again this will be covered in advanced training. In comparison to the Veo the Suunto will follow your profile as you ascend and reduce the overall near-surface interval based on how the offgassing profile has been generated. The Veo simply cannot handle the deco issue as its a recreational computer per its manufacturer. Read this article...
A sense of algorithm - Divernet

It is also important to understand that the RGBM algorithm is monitoring not only the time spent under pressure but also is measuring an abrupt change in pressure over time. If this change in pressure exceeds the a given (M?) value then an automatic stop is generated regardless of time underwater to allow any nitrogen seeds to be offgassed safely.

As for being too conservative, this is hard to say about the Suunto. If you look at printed tables and believe them and understand that the Suunto is following them (minus one box of time at a given depth) then only YOU can decide if it isnt right for your dive style.

Hope this wasnt confusing, I have been up and down chasing kids away from presents and food while trying to write this...

 

[DC53]

Thank you for the input. Indeed, after finishing the last bit of Master Diver, I plan on doing some tech instruction. However, there is still a problem here, it seems to me...

To be more specific, here are the differences in the way VEO and SUUNTO VYPER handle calculations. The below is based on using the Plan Modes, with Nitrox set at 34% for each, at P=0 and A=0 on the Suunto, and at 50% and 100% RGBM modes on the Suunto....

SUUNTO@50%RGBM--SUUNTO@100%RGBM-----VEO 250------Delta@50%--Delta@100%
Depth--NDLTime------Depth--NDLTime-------Depth--NDLTime---Min---------Min

60Ft.----80min--------60------76------------60------106------26---------30
70Ft.----58min--------70------56------------70-------71------13---------15
80Ft.----43min--------80------41------------80-------55------12---------14
90Ft.----33min--------90------32------------90-------41-------8----------9
100Ft.---27min--------100-----26------------100------32-------5----------6

(Hope the above is legible!)

As you can see the differences aren't that large near the MOD but become HUGE in the more moderate depths. The theory & application behind the programming of the two computers really seems to be dramatically different particularly in the mid depths (where most rec diving is done). If Oceanic is right, then Suunto is shortening dive time & depth by a large margin. If Suunto is correct, it would seem to me there ought to be an awful lot of DCS with VEO divers following the limits allowed by the computer. And all theory and tech study aside, 99% of us follow what the computers allow, not what the tables and the theory say.

By the way, although I have not taken tech courses (yet), I read everything I can get my hands on with regards to bubble formation and the factors that cause it, suppress it, exacerbate it and the problems that result from it. (And, I am also a physician.)

I am not sure there is an answer to this other than looking at the epidemiology of DCS with VEO/Oceanic computer users, vs Suunto users. Perhaps that data exists but any light anyone can shed on this is appreciated.

 

[RJP]

To be more specific, here are the differences in the way VEO and SUUNTO VYPER handle calculations.

Interesting that the VEO gives you more NDL at 70' (111 min) than it does at 60' (106min) - or is that a typo?

 

[QatarDiver]

DC53, Many thanks for the table of values. I also dive a Vyper Air and have similar observations when diving with buddies with other computers. I ended up setting my Vyper to 50%, thinking that changing from 100% to 50% might be a bit radical. I didnt realise it made so little difference. I'll stick with the Vyper, and with the 50% setting, and just accept the fact that it might go and beep at me before my buddies computer beeps at him/her.

 

[Katamuki]

DC, I would have been happy to look the data over but thats a screwball nitrox mix percentage. I dont have a quick table for 34 and am not willing to figure out EAD for each level to generate an NDL amount. 32 or 36 would have been easier...