Correct usage of Venturi effect lever

[BoltSnap]

I can't see any reason to have the cracking effort turned all the way in. On the primary 2nd stage, I don't see any reason to ever change it from all the way out for anything other than the example given previously - you're facing into a current and it's causing a freeflow.

If it is out of the mouth in water (surface or underwater), it will freeflow. I find it much better to turn it in until I use it. If you can find a setting to stop the free flow without turning it all the way, great.

Note: For storage, the venturi lever position does not matter, but the cracking effort adjustment should always be all the way out.

This is true, the turning in of the creaking effort adjustment need to be turned in only when in water otherwise it is left all the way out.

I bet you couldn't tell the difference in the inhalation effort with it in either position at depth (unless you are an ANSTI machine).
I appreciate that dealers say they cannot sell a regulator in North America unless they have these features.

It is VERY easy for me and/or for my student to discern the difference in the venture setting in the SP regulators.

 

[BoltSnap]

I'm curious about that. Why store it with the adjustment in a particular position?

Storing it with the cracking effort adjustment all the way out eases the pressure on the adjustment spring which is better for the spring in the long term. It will also prevent damage to the seat by lessening the pressure on it and preventing further wear on it.

 

[rsingler]

I'm curious about that. Why store it with the adjustment in a particular position?

The adjustment knob controls the amount of pressure on the poppet spring. With the knob screwed in, there is more pressure on the poppet as it presses against the sharp circular sealing edge of the orifice. With more pressure, during storage, the poppet seat is more likely to get a permanent indentation in its surface. That indentation is effectively like unscrewing the orifice a touch, because the pressure on the poppet between the sealing edge and the bottom of that groove is now slightly decreased. It's why a reg that's been left in storage may freeflow and need retuning or a new seat.

It's why the earliest Scubapro 109 chrome beauties came with a "key" that you inserted into the Scubapro "S" on the faceplate. That key depressed the diaphragm a little during storage and lifted the poppet off the knife edge of the orifice. Since no one supplies a "key" any more (or a place to insert it), I store my G-250's with a little short cylinder of PVC pipe that fits in the purge button hole. I wrap the reg so the button is depressed and there is no pressure on the seat.

It's why the "seat-saver" feature that Atomic uses was introduced. The seat saver is a spring behind the orifice that backs it away from the poppet seat when the reg is unpressurized, so the seat never takes a groove and lasts longer between services. All the complaints about water potentially getting in the hoses when you soak the regs unpressurized are (IMO) FAR OUTWEIGHED by the benefit of taking the poppet off the orifice during storage. You just soak your second stage in the sink and leave the first stage on the counter, if you can't soak it pressurized. Then soak the first stage while the second is on the counter (but make sure the intake is plugged, of course). Yeah, I think the seat saver feature is great. When I service my Atomics, the poppet seat is almost completely unaffected by the orifice at the 2 year mark.

Ah! I see @BurhanMuntasser beat me to it. Lol!

 

[stuartv]

I'm curious about that. Why store it with the adjustment in a particular position?

I agree that you'd be hard pressed to tell the difference in venturi lever position. At least, that's the case with my scubapro s600. I'd almost prefer a regulator which just permanently is in the "minus" position.

I think the first question has been sufficiently answered by others (like @rsingler) and I agree with them (for what THAT'S worth LOL).

With my S620Tis, I can't really feel any difference between the venturi level positions.

With the G260, I feel like I can tell a little difference. After it cracks and starts flowing, venturi in the Dive position (vs Pre-dive) does feel slightly nicer.

If it is out of the mouth in water (surface or underwater), it will freeflow.

I haven't run across a reg yet that had to be turned ALL THE WAY IN to stop it from freeflowing. Like I said, 1 turn generally seems like plenty. All the way in seems like a LOT of extra pressure to put on the seat, for no reason. Especially if it's your octo and you forget to open it back up after you finish your dive, so it ends up stored like that.

 

[stuartv]

It's why the earliest Scubapro 109 chrome beauties came with a "key" that you inserted into the Scubapro "S" on the faceplate. That key depressed the diaphragm a little during storage and lifted the poppet off the knife edge of the orifice. Since no one supplies a "key" any more (or a place to insert it), I store my G-250's with a little short cylinder of PVC pipe that fits in the purge button hole. I wrap the reg so the button is depressed and there is no pressure on the seat.

With the G260 and, I believe, the R395, you can push the center of the purge valve in and turn it about 1/8 of a turn, for storage. That holds the valve slightly open, as you described.

 

[BoltSnap]

I think the first question has been sufficiently answered by others (like @rsingler) and I agree with them (for what THAT'S worth LOL).

With my S620Tis, I can't really feel any difference between the venturi level positions.

With the G260, I feel like I can tell a little difference. After it cracks and starts flowing, venturi in the Dive position (vs Pre-dive) does feel slightly nicer.



I haven't run across a reg yet that had to be turned ALL THE WAY IN to stop it from freeflowing. Like I said, 1 turn generally seems like plenty. All the way in seems like a LOT of extra pressure to put on the seat, for no reason. Especially if it's your octo and you forget to open it back up after you finish your dive, so it ends up stored like that.

When you are making a water entry, giant stride for example, or swimming in wavy conditions, there is more chance of a free flow if it isn't all the way in or close to it. I tune my regulators to almost leaking air when open all the way out for the easiest cracking effort (but no leaks of any kind).

 

[kelemvor]

Huh.. glad I asked. Since I've been using FFM's lately, my S600's have been shelved indefinitely... and I've a few deco regs that hardly ever get used. I don't think those have adjustments so I might have to do something along the lines of what @rsingler described.

 

[caruso]

If your venturi lever is opened too high you just might look like this

 

[rsingler]

If your venturi lever is opened too high you just might look like this

View attachment 459340

Actually, you're not wrong!
There are several regs that, when incorrectly tuned, will "cross over" into freeflow at certain air flow rates. Therefore, heavy breathing at the surface might be effortless, as the Venturi effect helps hold the valve wide open and delivers easy air. But at high gas gensity (e.g., several atmospheres of depth) the venturi effect becomes so pronounced that it changes from "slight cracking effort" into freeflow, and the second stage will blow air at you. Of course all you have to do is allow pressure to build in the reg by resisting the breath and the valve will close. But it can be a little uncomfortable, and you're increasing your (expiratory) Work Of Breathing.

There are positions where you can't do that however, like inverted (where the exhalation valve is higher than the center of the diaphragm), and once a freeflow starts, it won't stop until you return "right side up".

The lesson? Don't dive a poorly tuned reg when upside down at 99 feet!

 

[caruso]

Actually, you're not wrong!

I know. A venturi knob that is opened too much can leave a diver feeling like the air is going to inflate them like a balloon, it's an uncomfortable feeling to say the least.