Suunto Cobra Conservatism

Many, many times I've read posts saying "I've heard that Cobra's are on the conservative side".

Well, it's easy to check, no?

I'm looking at my PADI RDP, and, for example, it says that the NDL time for a 90 ft. dive is 25 minutes.

Now, using my Cobra simulator (P0 Personal Setting), I draw a profile where I drop to 90 ft., and at around 21 minutes it shows my NDL time goes to 0. So that's conservative by 4 minutes compared to the tables.

If I do a similar profile using the Cobra's conservative Personal Setting of P2 (my normal setting), the NDL time drops to about 14 minutes. So that's 11 minutes conservative compared to the tables.

So it seems that, at least in this example, when using the Personal Setting of P2 it's "way conservative". Would you also call the 4 minute (P0) number "way conservative"?

The cobra is a recreation diving computer. With that said, with a dive to 90 feet I don't think that the 4 minutes is "way conservative". We teach students never to push the limits of the tables. But students don't always follow what they were told. Perhaps Suunto builds in the extra cushion to account for new divers who don't always follow their instructors advice and push the tables and do a faster than normal ascent. Now if we are talking about a computer for technical diving, then that extra cushion would mean more time decompressing. I would be interested to see they gap for Nitrox tables. I'll have to find mine and compare the Cobra with the tables.

If you really want to see how conservative the Cobra is then you are going about it all wrong.

Do a fast ascent, reverse profile, or a very short surface interval and see how short your NDL will be on the next dive. THAT's where the conservatism really shows up (correctly IMO, YMMV).

You can test all this with the SIMDIVE mode dive simulator (section 4.2.1 in your manual). Note that there are two other simulation/planning modes SIMPLAN and PLAN, but SIMDIVE is the mode where you can actually button-press realistic dive *profiles* to see their effect on your NDLs.