Fine tuning Mares Abyss

[jwal001]

Hi,
Was wondering if anyone has a few tips for fine tuning Abyss 2nd stage. I have the correct manuals and instructions, i.e. setting demand lever to approx 8mm above the reg body. But i find fine-fine tuning involves a series of blind adjustments to the lever lock nut. Whereas with other regs, its a matter of adjusting the poppet body until the lever drops.

Can anyone suggest any tricks or tips?
Thanks

 

[rescuediver009]

unfortunately on regs with the lock nut on them and not adjustable orofice in the second stage, it is a little more difficult of easier depending on how you look at it. I don't know if the newest generation Abyss has the adjustable orofice or not. You know where it is right? Otherwise, you can leave the reg pressurized and remove the purge cover and diaphragm along with the brass ring that holds the mess together. Find the right size nut driver, usually 6mm I believe, and slowly loosen the nut. The air will eventually begin to flow. Turn it back just a notch. Place the diaphragm and purge cover in place and hold it there without attaching the ring. Ensure that the weight of the diaphragm does not create a trickle. If so adjust it accordingly. then you are god to go.

Now, sometimes you run into the problem of the entire seat assembly turning with the nut. In this case you have to add in taking off the hose and holding the seat casing in place with either the specialty tool or a small flathead screwdriver. Then turn the nut on the other side while holding the poppet in place with the screwdriver. Obviously this method cannot be done all in one shot and the reg and has to be depressurized each time you make an ajustment. It takes a little longer. If you minimuze the hoses connected while doing this method, you will find pressurizing and depressurizing is alot easier.

Hope this helps rather than confuse. Something that the manual and all the books cannot really help with.

 

[jwal001]

I don't know if the newest generation Abyss has the adjustable orofice or not. You know where it is right?

Adjustable orifice? Hmmm....i think i know what you mean? A plug you can unsrew, in the reg body opposite to the lever nut. Which makes acessing the lever nut easier?
Please correct me if i am wrong.

 

[rescuediver009]

It is not quite a plug, but rather a cone that the seat sits on so you can adjust the breathing resistance. Like I said I don't know if the current Mares has one. But here is a pic anyhow, it is number 1. (keep in mind this is not a Mares reg) Otherwise is everything else clear?

 

[jwal001]

It is not quite a plug, but rather a cone that the seat sits on so you can adjust the breathing resistance. Like I said I don't know if the current Mares has one. But here is a pic anyhow, it is number 1. (keep in mind this is not a Mares reg) Otherwise is everything else clear?

Thanks for the diagram!
The internals of the 2nd stage is quite simple, (looking for a exloded diagram actually!) the seat sits inside a seat connector, can adjust the distance that the seat extends out from the connector, but the manual recommends to extend the seat all the way out then retract it, screwing it counter clockwise 3 complete turns. Other than that all other adjustments are done by adjusting demand lever height. Have had 2 attempts at it, with the help of a friend whos knows quite a bit and are both struggling to get it just right. Dived yesterday to 10m. It was fine! Went for next dive and knocked my reg as i geared up and the 2nd stage started to hissss. Dismantled it and quickly adjusted it to stop the hisss, dived to 18m, but it wasn't breathing quite right???
Open to suggestions?

 

[Greg Barlow]

Thanks for the diagram!
The internals of the 2nd stage is quite simple, (looking for a exloded diagram actually!) the seat sits inside a seat connector, can adjust the distance that the seat extends out from the connector, but the manual recommends to extend the seat all the way out then retract it, screwing it counter clockwise 3 complete turns. Other than that all other adjustments are done by adjusting demand lever height. Have had 2 attempts at it, with the help of a friend whos knows quite a bit and are both struggling to get it just right. Dived yesterday to 10m. It was fine! Went for next dive and knocked my reg as i geared up and the 2nd stage started to hissss. Dismantled it and quickly adjusted it to stop the hisss, dived to 18m, but it wasn't breathing quite right???
Open to suggestions?

First, of all, the orifice is completely adjustable. The setting is somewhat critical, as the poppet will not retract the correct distance from the orifice. It the distance is too great then the valve will leak. If the distance is too short then the gas flow will be significantly diminished thus affecting the breathing.

Setting the lever height on the Abyss is a bit tough as there is no access port as with the other Mares second stages. Mares makes a lever positioning gauge that sits on the edge of the case to "ballpark" the height. I typically don't use it, as I adjust the lever so that gas begins to audibly flow when the purge button is depressed approximately 2mm-3mm. You can hold the two case halves together in your hand without the clamp ring installed to make this adjustment. After getting it set, then reinstall the clamp ring and test the setting by inverting the second stage into a container of water. Keep the mouthpiece completely vertical and slowly lower it into the water. The gas should begin to slightly flow when the water level is between the zip tie on the mouthpiece and the opening of the mouthpiece. The cracking effort should never be below 1.0" of water as it will free flow when in a horizontal swimming position due to the case geometry. I set all Mares primary regs to have a cracking effort of 1.25", with AAS set a 1.5". I've tuned more than a hundred, and only had one sligthly free flow with this technique. If you want to actually measure the cracking effort on the second stage, then apply a piece of masking tape to the housing and measure up 1.25" from the front edge of the retaining ring (closest to purge).

Greg

 

[oxyhacker]

While some Mares 2nds have something that appears to be an adjustable orifice, Mares does not describe it as such, nor recommend using it as such in the service literature, which just says to screw it out a certain number of turns and leave it alone.

The reason being, according to Mares, is because of the Mares VAD bypass, which blows air directly into the mouthpiece. If the orifice is adjusted too far, it can partially block the VAD port, degrading the stage's performance.

If you want to fine tune cracking pressure, Mares says to use the IP!

 

[EricQ]

This is one way to do it.Use a 5mm hex key to screw the orifice out a distance of 1/8"...I stand the assembly on a flat surface ,orifice down, and slide a 1/8" hex key towards the orifice to get the distance. Then I adjust the lever height same as Greg explained. This setting stops the reg from going into violent free flow whenever the purge is pressed.
you can use this as a starting point if you want more sensitive breathing effort.

 

[Greg Barlow]

I have standardized setting the orifice at 0.125" from the base of the connector. I use a dial indicator to make the setting. This is mid-range of Mares's recommendation of 0.118-0.138". The new Mares regs that I have checked typically fall within a few thousandths of this setting.

Greg

 

[rescuediver009]

While some Mares 2nds have something that appears to be an adjustable orifice, Mares does not describe it as such, nor recommend using it as such in the service literature, which just says to screw it out a certain number of turns and leave it alone.

The reason being, according to Mares, is because of the Mares VAD bypass, which blows air directly into the mouthpiece. If the orifice is adjusted too far, it can partially block the VAD port, degrading the stage's performance.

If you want to fine tune cracking pressure, Mares says to use the IP!

I would think that this is definetely not the way to do things. Not only do I think that it is incorrect, but no other manufacturer recommends using the IP as a cracking adjustor. I don't know that this would affect the VAD bypass. I would have to look at one.