Tuning Larger calibers seem much more efficient?

[Stubbers]

Im gonna definietly try it asap as i will have the opportunity. But what you mean with "balanced valve"? Just because till now i heard this expression only in marketing bullpoops and still have no idea what the balanced valve is.

You implied originally "non assisted valve" which is what I interpret as conventional valve, balanced valve is what FX has used for years and has becoming more regularly available on the market with higher end guns. They reduce the pressure seen at the head of the poppet by using a piston (or walls of a bore) that displaces that pressure on itself (a stationary piston) within the bore of the poppet, or in reverse, where the poppet is a piston.

-Matt

 

[Stubbers]

Another 'dry fire' perspective, is when you're hammer collides with the poppet stem, you're creating a momentary act of compression, where the poppet must lift off the seat to create air flow, and to do so must compress the air within the plenum, albeit very, very minimally, before you can let that chamber then decompress into your throat...

Heavier projectiles or immovable objects such as fully choked tp's OR as some bloke a few days ago loaded 12~ over sized slugs into his FX and it wouldn't fire at all...that creates too much back pressure, not allowing the act of compression to fully occur, denying the hammer to freely open the valve and let air flow through the barrel.....this isn't a bell curve effect that diminishes somewhere with lighter pellets where lighter pellets start becoming more efficient...its a slope, where lighter pellets will always be less efficiently capable then their heavier counterparts...

Heavier projectiles = more volumetric / thermal efficiency / energy efficiency
Lighter projectiles = higher peak velocity, lower peak energy / volumetric / thermal

Also, why do some valves literally self destruct or become damaged upon a dry fire? They're over driven...for the above reasons...cmon Scott.

-Matt

 

[explorer]

The efficiency is clear for me from the beginning and agree.
But this part is still unclear ....
Heavier projectiles or immovable objects such as fully choked tp's OR as some bloke a few days ago loaded 12~ over sized slugs into his FX and it wouldn't fire at all...that creates too much back pressure, not allowing the act of compression to fully occur, denying the hammer to freely open the valve and let air flow through the barrel...
What you mean with backpressure? The valve is closed by the differential of plenum and chamber pressure. Higher chamber pressure makes smaller differential and keeps the valve to open easier. The valve is opening to inside to way of plenum so the valve needs to compress the plenum air slightly in same way with and without pellet if the plenum pressure is the same ofc.

 

[Jez]

I have read all, most of the above posts and have to admit alot of it is beyond me but have always thought that .22 is more efficient than .177. You guys are very lucky to be able to have no power restrictions on you air rifles. Here in the UK with our sub12 fpe rule and my experience with springers at this power (sub 12) a .177 has a harder cycle to push the small and generally lighter pellet to its permitted velocity were as all being equal and swapping out to a .22 barrel velocity will diminish but you will end up with a harder hitting pellet and have to be carefully not to exceed 12 fpe.

 

[sb327]

In a conventional valve, the most significant event that affects closing force (and subsequently, closing speed) is the pressure at the stem diameter (acting as a piston). With a heavier projectile, the pressure is developed faster and higher than with a lighter pellet or a dry fire. To me, this is the most significant event that causes dry fires to use more air per shot.

As far as a larger caliber being more efficient, it has been explained well here.

These are just my opinions and each system has its own little quirks that can change how projectiles react. Therefore, the statements above are general in nature.

Dave

 

[explorer]

In a conventional valve, the most significant event that affects closing force (and subsequently, closing speed) is the pressure at the stem diameter (acting as a piston). With a heavier projectile, the pressure is developed faster and higher than with a lighter pellet or a dry fire. To me, this is the most significant event that causes dry fires to use more air per shot.

As far as a larger caliber being more efficient, it has been explained well here.

These are just my opinions and each system has its own little quirks that can change how projectiles react. Therefore, the statements above are general in nature.

Dave

Maybe im the stupid and dont know what a conventional valve looks like. What the hell guys?
How the heck the pressure behind the projectile can make the valve close faster?

 

[sb327]

If you draw your valve in the open position, it will become apparent that the pressure in the transfer port acts on the stem which is acted upon on the hammer side by atmospheric pressure.

Dave

 

[explorer]

If you draw your valve in the open position, it will become apparent that the pressure in the transfer port acts on the stem which is acted upon on the hammer side by atmospheric pressure.

Dave

The pressure acts to the stem but also to the valve surface on the left and as the surface of the valve (including the stem) is bigger than the stem alone on the right side the backpressure going to make its impact to left side (opening way of valve) i think.
No?

 

[sb327]

The effect of pressure at the valve surface to the left depends on the position of the poppet. If the poppet is open any significant amount, the pressure there is essentially the same as plenum pressure and therefore the differential doesn’t affect the poppet movement. Of course there are exceptions as I stated above where a gun is tuned to not fully open the poppet.

Dave

 

[explorer]

the pressure there is essentially the same as plenum pressure -and this is what makes it to close slower
Anyways, I did 10 shots with and without pellets with my PR900W Gen2 and with dryshots it consumed less of air. Im pretty sure there is a bunch of other rifles which works this way. So i think we can stop with the proving of our teories, move on, lets see whos rifle works this way or no.

 

[Stubbers]

To OP.

I did the math on the pressure drop difference between a .22 caliber bore and .30 cal bore as the projectile travels down it of equal length at 23"

The average was around 8%, which explains partially why you won't see the full difference in surface diameter gained swapping calibers. That would take the 46% figure down to 38% (op saw 35%). The remainder is likely the added friction due to surface diameter as I mentioned earlier, and whatever else I may be leaving out.

Changing barrel volume, pressure, pellet weight, % of bores porting, and various other variables, on either bore would result in skewing the above simple approach of using only bore diameter and the average difference of pressure drop behind the projectile down the bore.

-Matt

 

[Stubbers]

If a 'dry shot' over drives a valve to the point the hammer bounces off the rear of the valve, it will shut faster. This is also why some valves will destruct or cause damage on dry fire.

I know for a fact my rifle does not operate under these conditions with either conventional nor non-conventional valves, my .177 will empty much faster when I dry fire it down opposed to shooting pellets, likewise the lighter the pellet, shooting 7.9gr will obtain many less shots than shooting 16gr with the same hammer strike.

-Matt

 

[EPG]

To OP.

I did the math on the pressure drop difference between a .22 caliber bore and .30 cal bore as the projectile travels down it of equal length at 23"

The average was around 8%, which explains partially why you won't see the full difference in surface diameter gained swapping calibers. That would take the 46% figure down to 38% (op saw 35%). The remainder is likely the added friction due to surface diameter as I mentioned earlier, and whatever else I may be leaving out.

Changing barrel volume, pressure, pellet weight, % of bores porting, and various other variables, on either bore would result in skewing the above simple approach of using only bore diameter and the average difference of pressure drop behind the projectile down the bore.

-Matt

Awesome Matt, thanks for confirming that my 35% was a reasonable amount of energy to gain!

Wow, the best thing about this is that I have tunes of:

915fps in .22 shooting MRDs
850fps in .30 shooting 44.8g JSBs

Both calibers are accurate as heck with this tune!

And all I have to do is swap barrel and pellet probe. Takes less than 3 minutes with the Prophet to swap…

…Not only is the Prophet Performance V1 the easiest airgun to adjust (reg pressure & hammer spring preload) … its also the easiest rifle to NOT have to adjust, lol.

Got two Prophet Performance V1s and .177, .22 LR, .25 LR and .30 barrels. Just love this rifle - incredible.

- Ed

 

[Stubbers]

the pressure there is essentially the same as plenum pressure -and this is what makes it to close slower
Anyways, I did 10 shots with and without pellets with my PR900W Gen2 and with dryshots it consumed less of air. Im pretty sure there is a bunch of other rifles which works this way. So i think we can stop with the proving of our teories, move on, lets see whos rifle works this way or no.

View attachment 377751

View attachment 377752

Your gauge is more full without pellets? I am confused now...(never mind I see you said it consumed less air dry shot...heh, my brain hurts after I tested this and made so much noise)

(My test so far show identical air usage in .177, gonna try a larger caliber opened up, I could very well be wrong!)

 

[Stubbers]

Ok here is my conclusion for "do dry fires use more air" .

The larger the air/pellet ratio in favor of pellet mass, the more air you'll save compared to dry firing. I tested and confirmed this today. I do believe there is sonic choking occurring with dry fires where with a light enough pellet, it will use less air.

So I will apologize to Scott, he wasn't entirely wrong (nor right as it was a generalized bias towards light ammo, where it ultimately depends on caliber and most importantly air/pellet ratio)...but I do believe he isn't partially right for the wrong reason, and that is opinion, which we're all entitled to. (I believe sonic choking occurs with extraordinarily light pellets / dry fires, opposed to it being a sail effect, in fact there should be less 'sail effect'/drag on the poppet when there is sonic choking, and subsequently less air leaving the barrel, either scenario is plausible but I favor sonic choking)

Test gun : Unregulated Stock valved marauder in .177/.25.

In 25 cal the dry fire used a lot more air than shooting heavier weight pellets (this is a caliber I am most familiar with) (nearly 2x air use dry fire compared to 48 gr slugs...same tune / .14" valve but a .225" tp was used instead of .14", other than that small change only changed barrel)

In .177 shooting heavier ammo used less air shooting than dry firing, but lighter (10gr) pellets used a hair more than dry fire, and I mean a hair...I had to repeat the test about 3 times to make sure it wasn't neck and neck. I cannot confirm nor deny if I was bouncing of the rear of the valve. State of tune would effect this as well, if I reduced my hammer strike enough, eventually even the 7.9 gr .177 pellet will shoot with less air than the dry fire, or if I opened the ports enough to eliminate the sonic choke occurring...this is a .14" ported valve lol, my .225" ported valve behaves much differently, and doesn't experience as much sonic choking, and was not used in either .177/.25 test here...as its not in my hands right now. I am also at 11 psi atm vs many being at 13-14.7 psi, which means my dry fires *in theory* are less efficient than yours.

That to ME makes this a Lognormal distribution due to (what I believe is) sonic choking being introduced once you approach pellets that are abnormally below your ejected air's mass based on your available porting/pressure used, barrel length... (Opinion, not FACT)


(Similar to the blue line seen on this graph, where there is a cut off, and heavier enough ammo will always be more efficient than a dry fire.) (Observed opinion)

-Matt

 

[Emu]

Assuming same hit of the hammer to open for the same time the valve to release same amount of air on both calibers, the difference in efficiency need to become from a combination of surface of pushing and the length of the barrel.

 

[Stubbers]

Assuming same hit of the hammer to open for the same time the valve to release same amount of air on both calibers, the difference in efficiency need to become from a combination of surface of pushing and the length of the barrel.

Minus the pressure drop difference down the bore length, which is not solely tied to surface area.

 

[Stubbers]

SD1 = 3.14159*(SmallerBoreDiameter/2)^2
SD2 = 3.14159*(LargerBoreDiameter/2)^2

SD1 = .03812
SD2 = .07068

PD =((1-(SD1/SD2))*100)-√((1-(SD1/SD2))*100)*1.5

PD (Power Difference expressed in FPE) = 36% (this calculates the decrease from .30 to .22, one would have to extrapolate to get increase)


Not sure how this scales, with different barrel lengths, or even different calibers/states of tunes, but if you keep pellet ratio in excess of this result or just your sd1/sd2 difference, you should end up somewhere close using the above formula

 

[Stubbers]

 

[explorer]

First of all ... i was starting to re-read the efficiency thread on the beginning and im stuck at one thing.
47/72 = 35% gain in energy (and thermal efficiency) -how the heck you got this number? The increas from 47 to 72 is increase of around 53 percent.
It would be a 35 percent in case of drop. I hope your other calculations are with correct percentage calculations
If a 'dry shot' over drives a valve to the point the hammer bounces off the rear of the valve, it will shut faster. -it can be ...
Awesome Matt, thanks for confirming that my 35% was a reasonable amount of energy to gain! -yeah actually it was 53
Not only is the Prophet Performance V1 the easiest airgun to adjust (reg pressure & hammer spring preload) … its also the easiest rifle to NOT have to adjust, lol.
-need to deeply agree as a prophet 2 owner ... damn that rifle shoots extremely well even without tune not like an FX what without tune shoots 6 MOA groups
What is sonic choking? I googled for it but probably you dont mean this one ....