Mistral rebuild clarification question.

[Ghost95]

Morning all, hope you are doing well and getting some nice dives in.

I'm about to begin the rebuild of the new to me Aqua Lung Mistral and I want to make sure I understand something.

Because this is a single stage regulator, there is no IP to adjust correct? It's just tank pressure reduced to ambient and all tunning is done by the lever height adjustment right?

Are there any other tunning tweaks I need to know about?

Thanks for your time. Have a good day.

C-

 

[James79]

Morning all, hope you are doing well and getting some nice dives in.

I'm about to begin the rebuild of the new to me Aqua Lung Mistral and I want to make sure I understand something.

Because this is a single stage regulator, there is no IP to adjust correct? It's just tank pressure reduced to ambient and all tunning is done by the level height adjustment right?

Are there any other tunning tweaks I need to know about?

Thanks for your time. Have a good day.

C-

Yep, that's it. It is also upstream and unbalanced... so it will breathe easier as tank pressure drops. I haven't used a Mistral myself, but my Healthways Scuba (similar upstream single stage) breathes pretty stiff over about 2400 PSI, and rivals my RAM below 1000 PSI.

 

[jvanostrand]

Most mistrals directed air flow into the inhalation horn to create a "venturi" effect. Earlier models directed the air flow at the can or the edge of the horn. If you have one that directs air at the can or edge you can improve performance by directing it into the horn. You'd have to either replace the bottom can, or drill a new locating hole. There was also a difference in the length of the tube directing air flow. Some had a short, perhaps 1cm tube and most had one about twice as long..

Mistrals are great breathing regs.

You shouldn't need to do anything else for performance, although there are new "wagon wheels" that have tapered edges to smooth air flow into and out of the mouthpiece. There are silicone reproduction parts like hoses and mouthpieces that make it more comfortable. There is also a "duckbill eliminator" that supposedly eases exhalation too.

 

[Ghost95]

Yep, that's it. It is also upstream and unbalanced... so it will breathe easier as tank pressure drops. I haven't used a Mistral myself, but my Healthways Scuba (similar upstream single stage) breathes pretty stiff over about 2400 PSI, and rivals my RAM below 1000 PSI.

Thanks James.

 

[Ghost95]

Most mistrals directed air flow into the inhalation horn to create a "venturi" effect. Earlier models directed the air flow at the can or the edge of the horn. If you have one that directs air at the can or edge you can improve performance by directing it into the horn. You'd have to either replace the bottom can, or drill a new locating hole. There was also a difference in the length of the tube directing air flow. Some had a short, perhaps 1cm tube and most had one about twice as long..

Mistrals are great breathing regs.

You shouldn't need to do anything else for performance, although there are new "wagon wheels" that have tapered edges to smooth air flow into and out of the mouthpiece. There are silicone reproduction parts like hoses and mouthpieces that make it more comfortable. There is also a "duckbill eliminator" that supposedly eases exhalation too.

Thanks. It appears the Venturi tube on my mistral is longer than 1cm, and if I remember correctly from my disassembly it was pointed very nearly down the hose.

On a side note, for some reason I "feel" that my DAAM with an improved silicone duckbill exhales easier than the one with the eliminator. I think the wagon wheels are the same but not 100% sure about that.

Crazy how simple this regulator is.

Thanks all. Have a good day.

 

[James79]

Crazy how simple this regulator is.

Beauty in simplicity.... from what I gather the go roughly eons between rebuilds if rinsed well.... just nothing really to go wrong with them!

 

[Scuba Lawyer]

Be sure and tune the lever height using a tank with less than 500 psi. I use 300 psi. Adjusting lever height on a full tank will result in free-flowing at the end of the dive. Don't ask me how I know this. M

 

[Ghost95]

Be sure and tune the lever height using a tank with less than 500 psi. I use 300 psi. Adjusting lever height on a full tank will result in free-flowing at the end of the dive. Don't ask me how I know this. M

Thanks for the tip. It makes perfect sense if you think about it but in the fun of the rebuild I might have missed it. Thank you for possibly eliminating a headache.

 

[John C. Ratliff]

Yes, the lever height is critical, and I've found that about 1/4 inch above the box height is better than the recommended by U.S. Divers Company that it be at the box height. Again, as Scuba Lawyer says, do it at low tank pressure. What I do is adjust it up until there is a slight leaking of air when I put the two boxes together with the diaphragm. Squeeze hard to ensure that there is no leakage, but the maximum height will give the best breathing. There is a nut that needs to be loosened to raise the lever height, then a wheel (#7, Adjustment nut) that can be turned to increase or decrease the lever plate (#6) to adjust the height of the levers.

SeaRat

 

[Ghost95]

Thanks for the tip John.

I'll be tinkering with this when I get home from my rotation at work. I bought an SCBA adapter so I can fill a pony bottle at work and play with these projects in my off time at work.

Have a good day.

C-