ADVANCED TUNING for those with JSAR Raptors or the SS-2 Balanced Valves

[Motorhead]

Let me start with saying what I'm going to disclose myself and Travis Whitney of JSAR had discussed Many times in the past 6+ months or so as the R&D behind the scenes was happening.  We had the conversation that at some time these tuning traits should be brought to light and shared.  In the past 6+ months further testing and tuning with an Actual Raptor valve ( SS-2 in function ) retrofitted into my WarP , have got to get some really good data and more importantly some Cause & Effect when changes are made in TRANSFER PORT SIZE ... which for now will be the focus of this thread.

To recap on how these valves work ... simply put is by having a DUAL use poppet head, one larger diameter side sealing the valve throat as is typical, Other end being reduced in diameter and extended into a sealed tube / chamber and sealed via an o-ring.  * What has happened is the pressure within the valve internal space bearing down on the closed poppet has had PART OF IT'S TOTAL AREA isolated by having the opposing end up in the o-ring sealed chamber. THUS the pressure exerted on the poppet seat is greatly reduced and the valve will break free and open far easier with not only LESS hammer weight, but less strike energy as well ( Softer hammer spring, less hammer stroke etc ..   )

While this sounds all good & fine we all like easy cocking fast cyclic actions  there is now the issue of getting the valve poppet to close quickly and this by design utilizes a partially hollow valve stem that goes from just under the poppet head within valves throat up into the end of the poppet within the chamber.  * So at any time when valves pressurized the chamber at the upper end of poppet is at atmospheric pressure being vented via the poppet stem into throat, then out the barrel. Yet there is pressure surrounding the poppet that is kept from escaping via the o-ring mentioned earlier sealing it.

Here is where we're going .... WHEN THE GUN IS FIRED there is a spike in pressure filling the valves throat and ultimately launching the pellet or slug.  In that very short time span that released pressure travels up threw the partially hollow valve stem and INTO the chamber pressurizing that space.  In this instance the poppet which has traveled inward within the chamber via the seat side being lifted is now acted on by the pressure filling chamber and is quickly pushed back down the chamber violently closing the seat.      Crazy stuff !! and now with this base knowledge to chew on we will address the purpose of this thread 




Understanding the hammer that opened the valve, it's weight mass etc is also holding the poppet from closing very fast being reliant on the Balance chamber to push back so hard the hammers lift on poppet can be stopped with hammer forced to then go back the direction from which it came and allow poppet to close again.   This is the tuning trick that for those incline will find HUGE efficiency gains, lower muzzle report and less air used in general at any given power level.

Because these valves have such generous port values, huge throat and transfer path they BREATH SUPER WELL releasing mass volumes of air that produce Really big power !!
Controlling there DWELL ( How long the air is flowing is dwell ) and this is controlled by HOW EFFECTIVE THE BALANCE CHAMBER is to sense the mass flow and SHUT IT DOWN !!!
For once the pellet or slug is underway and moving 1/2 the barrel length or less, releasing more air IS NOT DOING A THING or very little and somewhat caliber & projectile weight dependent.

TRANSFER PORT SIZE MATTERS and is a MAJOR major tuning parameter with these valves and Bigger IS NOT better in many instances belief it or not
AS WE CONSTRICT THE OUTFLOW or air leaving valves throat we are INCREASING the amount and strength of the air that makes it into the balance chamber / tube and gets the valve to close.
Valve opens EASY and breathes volumes, but control of getting it shut down is paramount to Efficiency & a Low muzzle report.

Below is a test recently done while shooting NSA .22 caliber slugs. hammer weight, stroke, spring tension never changed ONLY TRANSFER PORT SIZE.  * Barrel is @24" with an elongated transfer port offering FULL caliber port specs so it to breaths to the bores caliber 100%.  Pressure regulated at 2200 psi.

BIG transfer port at .250" being slightly greater than caliber @ 935/940 fps
>Caliber spec transfer port at @ .210" @ 980 fps
Smaller yet transfer port at .175"  @ 980 fps
Smaller yet transfer port at .160"  @ 960 fps
Smallest transfer port tried at .140" @ 915 fps

Whats really interesting is listening to the gun fire with the top 4 tests especially ( All Shots are exceeding 50 ft lbs ! ) in .22 caliber too.     NOISE, that of the residual after the shot released air that is the heard muzzle report.

The largest port arguably having excessive volume poppet to slug and the least efficient with a good WOOOSH sound upon firing. * Still making great power !!
With the .210 transfer the report was notably quieter and as a tuner you know the dwell was reduced. YET it making MORE power ... kewl !
With the .175 transfer the report becomes a muffled SNAP and is quieter yet again.  Whoa same power too ! Now I know we're wasting less air and dwell has really been cut back.
With the .160 transfer the report sounds like a 12fpe pcp with LDC ... Sounds like a cricket farting being weirdly concerning the guns power had tanked, yet we only lost 20 fps.
Finally  the .140 transfer ... about like the above just less power tho still FLINGING these 24.8 slugs with authority !


With all my testing coming to light in this shared manor, I not going to get into efficiency number beyond a recent check I just did a few days ago.  That being when the .210 port was fitted and thought I was done and giggle happy. Efficiency numbers crunched at 1.29 fpe/cu in shooting the NSA 24.8 at the above speed which was Awesome.   Having just run these smaller transfer port tests just hours ago ... IT'S EVEN BETTER and going to keep the .160" transfer in place for now and see just what the efficiency does.  * Have a fun shoot next weekend and will be shooting the gun quite a bit and able to really gain some extensive real world numbers.







Hope this all makes some sense, was not overly long winded and you gain some knowledge from it 

Scott S
 

[Rat Sniper (AKA: PaulT58)]

Wow!  Most of this went way over my head, but it looks like the .160 TP is an optimal set-up!  Cool stuff!

[ranchibi]

Scott, what you wrote made me understand how the balance valve works in my Raptor and why it’s so flexible and efficient. Thank you!

[bear air]

Thanks for sharing all this valuable info Scott. Keep it coming!!!!!

[jarmstrong]

  WOW Scott, it all makes perfect sense
this is this first use of a variable transfer port makes sense to me. in other guns choking the port for lower power wastes air on Fx and Hatsans
But would be desirable for the SS-2 tunability,,,just WOW

[RDB]

Thanks for taking the to be long winded! Lots to soak up in those few paragraphs.

So say you wanted to make it a 35fpe pellet shooter, you could choke the t port even more and get some super efficiency numbers if im follow correctly? Less t port= shorter dwell? I would imagine 2.0 wouldn't be too much of a stretch.

[Tonycalves]

Great info! Thanks for the break down. Is the gun your testing on regulated?

[cobalt327]

"Pressure regulated at 2200 psi."

Info opens up some interesting possibilities...

[rsterne]

Great writeup, Scott.... It sounds like when you choke up on the transfer port you are raising the pressure in the throat of the valve, which causes the pressure in the balance chamber to rise faster.... therefore closing the valve quicker.... Interestingly, you are still getting enough air in the barrel to stay very close to the plateau velocity....

The only thing that didn't fit with my expectations is the reduced velocity with a 1/4" transfer port.... Then I reread your post and realized that you are only working with a .22 cal barrel.... Therefore you are creating a pressure drop between the throat and the pellet which is unnecessary and undesireable.... My guess is that is having two effects.... It is reducing the pressure available to push on the pellet.... while simultaneously causing that lower pressure in the balance chamber to be less effective in closing the valve....

In any case, whether that explanation is valid or not.... NICE JOB !!!.... and thanks for sharing.... I would ask you one question.... Is there any possibility that in the test with the 1/4" transfer port that the hammer could be hitting the back of the valve (because of the reduced closing force)…. and therefore bouncing back and reducing the velocity?....

Bob

[Motorhead]

Thanks for taking the to be long winded! Lots to soak up in those few paragraphs.

So say you wanted to make it a 35fpe pellet shooter, you could choke the t port even more and get some super efficiency numbers if im follow correctly? Less t port= shorter dwell? I would imagine 2.0 wouldn't be too much of a stretch.

Understand these valves are primarily focused on MAKING POWER ! .... If your application can be well served by a conventional valve at low to modest power there is little point to go this route IMO.

As too ever smaller transfer size, there is a limit quickly reached that happen sooner with a heavier hammer and increased tuneablity with a light hammer.
This simply because at any given pressure within the valve and throat, and that pressure threw the small hole / path connecting to a given area balance chamber ... can and will only exert a given amount of push back based on the pressure / area within the chamber.

As a hammer gets heavier the inertia it carried via the hammer spring throwing it to open the valve is less effected by the closing forces created by the chamber getting pressurized.  Lighter the hammer greater is the ability to influence its motion by the opposing force created by the chamber / poppet pushing back. 

Yes some stuff going on no doubt ... Cause & effect, just keep whats doing what and it starts to make more sense.

The limit of reduced transfer size becomes relative to being able to stop the hammers LIFT and reverse its direction with any control.   As you go smaller it is still somewhat GREY to really get a handle on IF OR NOT ? the power finally drops away because DWELL is so controlled/ chopped ? ... Or the Restriction in flow controlling the power potential ?  * I think this has a large bearing on a hammers weight where a heavier hammer over powers the closing effects of the chamber less so than a light hammer.

ying - yang to be sure ....

[Motorhead]

. I would ask you one question.... Is there any possibility that in the test with the 1/4" transfer port that the hammer could be hitting the back of the valve (because of the reduced closing force)…. and therefore bouncing back and reducing the velocity?....

Bob

Can't say ... When it happened originally a few days ago actually replaced the .250 transfer with the .210 transfer no less than 3 times figuring a pinched o-ring, misaligned port or something ... validating the velocity drop on the big port and rising with the smaller one.   Being the firing system is only using 30 grams of hammer weight and an SSG did not think so.
Previous testing with my other balanced valve ( WAR converted valve ) which opens even easier, my PEAK power was still sitting at @ 980 fps with the 14.8's or 1020 fps with the 23's  THIS BASED ON REGULATOR SET POINT and available air within plenum.   Raising pressure the power rises and less pressure it becomes slower. 
Getting this DROP may very well be excessive lift and the kinetic rebound of the hammers striker off the back of valve body simply don't know

Scott S

[Buldawg76]

following

[Rohmpm]

I have been seriously considering a Raptor and this may be the final reason to place my order.
1. Are the transfer ports replaceable?
2. If so, what level of disassembly is required
3. What affect on the different transfers will reducing the regulator set point produce
Thanks

[Motorhead]

I have been seriously considering a Raptor and this may be the final reason to place my order.
1. Are the transfer ports replaceable?
2. If so, what level of disassembly is required
3. What affect on the different transfers will reducing the regulator set point produce
Thanks

Yes transfer ports are replaceable by removing the upper receiver & barrel assembly from the lower tube.
* THE PRODUCTION JSAR RAPTOR uses a different weight hammer, different operating pressures, different calibers etc etc etc ….  This post if for those who wish to TUNE there guns or valves based upon there specifics at hand.  There is no way to have a paint by numbers give me this size transfer etc without a whole lot more folks having them and giving tangible input as to what they find optimal ..  We understand it, can cover the mechanics / pneumatics, but shy of a sure fire cook book. 

I have no official affiliation with JSAR and can't speak to what the future holds for manufacturer provided fine tuning parts or pieces.

THIS IS A TUTORIAL for those who wish to spend the time and effort to FINE TUNE beyond factory spec / as delivered guns or valves.

[KnifeMaker]

And I thought My excitement was already peaked! Oh yeah, this is gonna be "Special"! 


Knife

[Blutroop]

I have one of the gen 2 valves. I am on the fence about building up a rifle though as I’m really liking the size and weight of my prod better. I’m having a hard time getting all the power I want out of a prod in .172 (so far hit 755 fps with a 26gr slug) but it appears after reading this the gen 2 valve could be overkill for .172? I may have to build up a different caliber just to utilize my valve to it’s full potential..

[Rocker1]

 Great Stuff Scott thank you. David

[darkcharisma]

thx for the insight into those efficiency numbers

[rsterne]

Jeremy.... I don't think you have to worry about having the valve "too big".... Last winter I made my own version of the SS-2 valve (it started in my thread on developing a simple balanced valve)…. sized for a .357 cal.... I successfully used barrels in .308, 7mm, .257 and .224 caliber, just by changing the transfer port diameter to taper the (large) valve exhaust port down to the size of the barrel port.... A bit of playing with the hammer spring preload, and all 5 calibers worked great....

Bob

[Motorhead]

I have one of the gen 2 valves. I am on the fence about building up a rifle though as I’m really liking the size and weight of my prod better. I’m having a hard time getting all the power I want out of a prod in .172 (so far hit 755 fps with a 26gr slug) but it appears after reading this the gen 2 valve could be overkill for .172? I may have to build up a different caliber just to utilize my valve to it’s full potential..

Adding additional info ... In .172" you have such little area for the pressure to work against that the velocity achieved is going to be more tied to PRESSURE than valve output volume.
In a P-rod, 1720 sized air tube running at high pressure to get any speed ( providing as well sufficient barrel length ) your not going to have many shots available before pressure become too low for the power you got while pressure was higher.

In small calibers at the upper power levels in said caliber ... PRESSURE wins the day and there is no work around.