1st and 2nd stage effects on performance

[meisburger]

I have an old Brut regulator set I bought used eight years ago that I keep on a tank by the pool, and an Oceanic set I bought four or five years ago. Neither breathes very well, but the Oceanic is worst. Yesterday I picked up Aqualung Titan, and popped on one of the Brut 2nd stages as a second. Both breath nicely in the pool, but I noticed the Brut is smoother and quieter than the new Titan. I think this suggests that the first stage has a lot more effect on breathing performance than the second stage. Is that correct?

I think I'll try the Oceanic 2nd tonight and see how it breathes. I've tuned second stages, and will see what I can do on the new Titan.

Tim

 

[DA Aquamaster]

There are two things going on here.

1. The stability of the intermediate pressure in the first stage is key to getting good performance from the second stage. If the IP drops excessively on inhalation (due to either a low flow rate of the first stage or excessive lag in the regulator finally producing adequate flow) the performance and flow rate of the second stage will be affected.

With a first stage like the Brut, there is very little internal volume and very little intermediate pressure air to draw on during the initial inhalation, so lag in the system is a real performance killer.

2. At the same time, while I dislike Sherwood first stages in general, I have found their simple and inexpensive down stream poppet designed second stages to be surprisingly good performers when placed on a good first stage. In the shop, it's common to have a "cheap" Sherwood second stage used as an octo on a quality first stage that is capable of being tuned to provide as good as or even better performance than the "expensive" second stage that came with the other company's first stage. As you have noted, they breathe much smoother than they have any right to based on their price and appearance.

So in short, a quality first stage is required to get peak performance from a good performing second stage, but both stages have a significant impact on over all performance and both are only as good as the weakest link.

 

[meisburger]

Thanks DA. I don't know why I assumed the 2nd stage was most critical to performance. As you explain it, it makes sense. Since it is so easy to swap things around, i think I'll try several of the 2nd stages I have lying around on the new first stage.

Cheers, Tim

 

[jmps]

Thanks DA. I don't know why I assumed the 2nd stage was most critical to performance. As you explain it, it makes sense. Since it is so easy to swap things around, i think I'll try several of the 2nd stages I have lying around on the new first stage.

Cheers, Tim

Tim,

It would be really interesting to compare the Brut second to a Titan LX second on the Titan if you had access to one.