Weird Venturi Designs - Scuba Tech Tips: S16E03

Most new regulators include venturi assisted breathing but what does that mean? Alec shows 3 weird venturi designs and explains how venturis help divers breath.
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[@vincentsubmarinismo774]

Always a pleasure Alec. Thanks for sharing 🤿👍🇬🇧

[@AlecPeirceScuba_SeaHunter]

Glad you enjoyed it A

[@montypythonish]

Not many more experience drives that Alec. Definitely knows his stuff. Thanks for all the many years experience.

[@AlecPeirceScuba_SeaHunter]

My pleasure! A

[@dalerichardson8842]

Always helpful and entertaining Alec, many thanks 😊

[@AlecPeirceScuba_SeaHunter]

Happy to hear that! A

[@bloodymarvelous4790]

Finally someone who explains what the Venturi is actually for. This is one of your gems Alec. So many people will tell you the Venturi lever interrupts a freeflow, but that's not what it does. The Venturi effect is that the pressure drops as the speed increases. This will maintain a vacuum in your second stage, which will keep the diaphragm pulled in and the airflow going. That forces more air into your lungs. If your second stage doesn't have a Venturi control lever, it's set up so it won't freeflow. If you have a Venturi control lever, you can make it deliver more air, but that also makes it more prone to freeflowing, because once the valve is open, it stays open until it meets resistance. If the regulator is in your mouth, the resistance will come when you close your airway. If it's not in your mouth, you'll need to shove a finger in the mouthpiece to provide resistance Most regulators nowadays will come with a Venturi lever, but you can breathe fine while it's in the "pre-dive" setting.

[@AlecPeirceScuba_SeaHunter]

The majority of regs have a venturi but to give divers a lower price, some regs don't have them. It give the maker a path to upsell. A

[@mikkel4606]

Hey Alec. great video! been watching a bunch of your videos for a while and i love all the interesting things you show! its great to hear the history of scuba from someone who has actually been through it all.

[@AlecPeirceScuba_SeaHunter]

Thanks, lots more to share from this stone age diver. A

[@diverdave4056]

…mmm…🤔 and my 47 year old - Dacor Parker 900s are still working perfectly since you fine tuned it for me ! THANK YOU AGAIN ! 😘

[@AlecPeirceScuba_SeaHunter]

Great to hear and keep on diving. A

[@TerryRossi]

That dacor venturi design is really cool. As a new diver I am sucking on that regulator like a mad man!

[@AlecPeirceScuba_SeaHunter]

Maybe a peak performance buoyancy course will help with extending your air time. A

[@ErSlickVic]

i love this guy. thanks for all the info

[@AlecPeirceScuba_SeaHunter]

I appreciate that! A

[@josephdracula7487]

👍😎🇵🇭🤿I great explanation!

[@AlecPeirceScuba_SeaHunter]

Thanks! 😃 A

[@RichardEPGodfrey]

Another awesome video ... I've been using Mares Abyss regs for years which I find to be incredibly 'easy' to breath from but now I finally know why 😂 ... thanks Alec !! 🏴󠁧󠁢󠁳󠁣󠁴󠁿

[@AlecPeirceScuba_SeaHunter]

Nice to know the history behind your reg right! A

[@jacquespoirier9071]

venturi is the principle that is based on the bernoulli's equations and it is used in all carburetors including the constant velocity ones ( SU, Stromberg ) to name a few this technique applied to a diving regulator is a refinement of an excellent design that takes age. very good topic very good video

[@AlecPeirceScuba_SeaHunter]

Great point! A

[@barryinkpen6026]

I still have a couple old regs that I use occasionally that still work like new and can still be serviced. One is a Swimaster MR12 and the other is a Mares MR12-2. One has the venturi and the other does not but otherwise they are identical. Mares chose not to change much in this reg when they bought out Swimaster.

[@AlecPeirceScuba_SeaHunter]

Mares regs still have the "bypass" pipe on their regs. Kind of like a signature look but it still works just as well today. A

[@Dive-D]

DACOR Pacer's have the Venturamatic System. Big difference is, the venturi is automatic and Lever flap helps it to never free flow when venturi is on demand. Any other regulator in the market with a venturi will always free flow, if its automatic or manually set to, it doesn'tmatter. In addition which you didn't mention is that the mouthpieces right chamber is actually the Water Guide Chamber forthe (Anti-Free Flow Device) or AFD which will not let the PACER free flow underwater since its a vacuum that changes pressure in the diaphragm. It's fascinating how DACOR design this fabulous innovation that works together. DACOR's meticulous 24 year development of this innovative system showcases its flawless functionality and cohesive design. Really amazing regulators and breathing effort still tops todays regulators.

[@AlecPeirceScuba_SeaHunter]

I dove, sold, repaired and loved Dacor regs. Sadly sold my last one years ago. A

[@owenmougenot712]

Hi Alec. I always thought those metal flaps inside the older regs was to redirect your breathing out exhaust toward the valve to warm it slightly and reduce the chance of it freezing. Even us old guys can learn something new, ok I might have known that but just forgot it. Take care Owen m

[@AlecPeirceScuba_SeaHunter]

Lots more to learn from this old guy. Take care Owen. A

[@LarsSveen]

I have a reg that I thought had a manual venturi, but when I opened it, I noticed that all the switch did was limit how far the valve lever could depress. That's kind of an odd design that I'd love Alec's thoughts on.

[@AlecPeirceScuba_SeaHunter]

I can't place that regulator. Do you know the make/model? Trying to picture it, I'm not sure how that would create a venturi effect. I wonder if you are turning it the wrong way. That is, it may in regular mode when the lever is restricted & in venturi mode when not. The higher flow of air when the lever is wide open may be considered a venturi effect.

[@duncan2565]

Hey Alec, great video and finally clear to me. BTW are we ever going to see Kevin? lol

[@AlecPeirceScuba_SeaHunter]

Probably not. He has a face only for radio (his words not mine). A

[@maxtorque2277]

BTW, worth noting that on any modern regulator, say since about 1985.... 😀, Work of Breath (WOB) is pretty much entirely dominated by exhalation effort not inhalation effort, thanks primarily to well designed venturi systems, where the reduction in pressure across the first stage (IP -> ambient pressure) generates work used to help push air into the divers lungs. When you breath out, there is no such helping hand, and until recently a lot of regulators had high exhaust valve losses. Modern regs, esp. plastic ones, now can be designed to help reduce these losses, with nice smooth transitions and throats, and by using very flexible silicone exhaust valves, and by using external guides to try to form nice smooth bubbles in the water. But still something like 70% of the WOB is caused by the exhalation action !

[@AlecPeirceScuba_SeaHunter]

Thanks for the idea of a video on WOB. Viewers may want to learn more about how effort is measured. A

[@maxtorque2277]

@@AlecPeirceScuba_SeaHunter yup could be an interesting video 🙂

[@Caderic]

It is almost like positive pressure/forced systems like in aircraft, SCBA or CPAP. Almost. Like cousin.

[@AlecPeirceScuba_SeaHunter]

Ok lets go with distant cousin. A

[@Caderic]

@@AlecPeirceScuba_SeaHunter LOL, your right, probably distant cousin...Kissing cousin? LOL As always, love your videos. I would love to have half your knowledge, here and the ranch. Ironically, I came across both channels about the same time, looking for two completely different things.

[@renatogodinhorg]

🤩👌💥👏💥👏💥👏💥👏🍻

[@AlecPeirceScuba_SeaHunter]

Thank you very much. A

[@maxtorque2277]

On the Dacor reg at 5:56, are you sure the little flap on the actuation lever INCREASES the venturi effect? I suspect it actually REDUCES the effect it in order to prevent freeflow from excessive venturi effect? This is why the little flap is twisted, because that acts to push the airstream from the outlet hole sideways and AWAY from direct impingment on the the curved guide fins in the mouthpiece tube. Reducing the flow through the venturi path and increasing it through the main path effectively means a higher pressure acting on the diaphram. This is suspect means they have set the reg up to have a lot of venturi at low flows (ie very easy normal breathing) but use the little flap to limit the venturi effect at high flows to prevent the reg from feeling like it is "Blowing up" the divers lungs and helping to prevent out-of-mouth freeflows?

[@AlecPeirceScuba_SeaHunter]

I'm going with increases as I serviced and used a Dacor 900 for decades. A

[@maxtorque2277]

@@AlecPeirceScuba_SeaHunter I just commented on the apparent angle of the little fin, which as the lever depresses seems to actually divert the 2nd stage air exit jet from pointing directly at the ventury tunnel 😀

[@richardstratford9419]

Did AMF swimaster borrow this from Mares?

[@AlecPeirceScuba_SeaHunter]

Going by memory without my morning coffee, it's the reverse. Mares in 1976, sold AMF/Swimaster MR12 II branded regs. Kevin researched this for me from his cataloge collection. In 1977 - 1979 the Swimaster catalog showed the MR12-II with the AMF brand. When AMF/Swimaster folded, Mares bought the company and it has been called the Mares MR12 II since. It was only about 3-4 years before Mares took over and its still make in 2023. Hope this helps and I have the facts right. A

[@benheckendorn2696]

Hi Alec, again such an amazing tec tip. 🫶👍 I guess they mean easier, because it may feel easier to breath. And of course, they want to sell so they may tell it's much easier to breath. I would say if it's not this much more expensive, a ventury is worth to have. ❤️

[@AlecPeirceScuba_SeaHunter]

Absolutely! A