.22 synrod max tune ????

[shorty]

So, I have been reading Bullfrogs "exhaust port and transfer port" post or topic and thought is was a really good post along with Motorheads "light hammer" posts. Bullfrogs 70fpe .25 mrod is a power house. This just made me want to see what my stock .22 synrod is actually capable of because I definitely want to do a hog hunt with it. Even though I usually just run the gun at 15 to 20 fpe for 70 or more backyard shooting shots.

I only had a couple heavy weight pellets (19.09 barracudas) to tune with but I was able to get 18 shots at or around 37fpe. As far as I know the .22 synrod or Mrod was only doing 35 fpe max with a very low shot count (<10 shots) stock.

I was able to hit 18 shots all above the 35 fpe and most near or over 37 fpe and the gun was not at max. Something strange happened around 2500psi and 18 shots which I can figure out. Below 2500psi the gun changed it's tune (sound). It almost sounded like a quick blast of air and then fewwwwww. I stopped the shot count there.

So my question is what happen? I plan I getting some 21 grain pellets because I think my .22 synrod will be able to hit over 40fpe with a minimum of 10 shots (good enough for hunting bigger game)
and
If the .22 synrod really does have some of the .25 internals, shouldn't we be able to see some 50fpe shot counts with the .22 synrod?

If there is something that can be done to the .22 synrod that will allow for 50fpe and still be able to tune for backyard plinking with extremely high shot count I am all ears and willing to learn.

Here's my shot 1st attempt at a max tune on the .22 synrod.

[Motorhead]

Running a PCP as a DUMP gun w/o regulation the tuning is pretty straight forward and most understand it.
Go after BIG POWER then the flow path needs more area to get the pressure pulse behind pellet quicker and with higher amplitude.

BOTH the .22 & .25 Syn-rod valves run raised seat poppets.  A .22 will benefit by REAMING throat to .250" and opening transfer hole within valve body & Transfer tube to @ .150"
This will give you quite a bit more power and tune down fairly well if need be ... but WILL NOT be as efficient on air as the factory stock specs are.

Look at it like this ....
Small block Chevy with factory heads & cam can make near 20 mpg and a comfortable 250/275 HP
Add free flowing fuel y heads and a cam to UP the horse power ... it will make 350 + but at the expense of gas use and mileage no matter how easy you are on throttle.

PCP's are the same thing ... want power ? it's going to cost you in mileage and efficiency even when throttled down taking small sips 

** There are MANY ways to balance and make the most from power tunes ... but that is not the discussion we're currently having here.

JMO,
Scott

If you simply wish to go after EASY power with heavy pellets and will forgo low power / high shot count use 
Throat at .250 & underturn poppet stem within throat to @ .100" or use a ATA poppet if you can get one  ... Transfer hole at @ .170" ... Poly tube Transfer tube of same I.D. ... Drill & deburr barrel at .170" ... 10 or 12# hammer spring. 

Have fun !!

 

[shorty]

I kind of understand the airflow concept with opening and polishing ports and running a dump gun. But, want I was really trying to understand is what is happening at the 2500psi point.

Can 2500 psi and lower still achieve high fpe (>35fpe) no matter what size transfer port sizes or regulation ?

[Motorhead]

Can 2500 psi and lower still achieve high fpe (>35fpe) no matter what size transfer port sizes or regulation ?

Generally NO .... as pressure decreases so does the potential energy that can be extracted from it.  To get the most energy from the reduced pressure the passages and plumbing must flow better.  Smaller ports ... and/or lower pressure in general = lower power.