Tuning Dual hole transfer port power increase without matching probe...

[ladwict]

I have installed a HUMA dual hole transfer port ( newest version) in my Wildcat MK3 .22. I have the option to install it with or without matching pellet probe . ( matching from HUMA or leave FX original probe in) 

Now i have tried first with leaving the original FX probe and this already gives a staggering 35 fps velocity increase ! How is it possible that when you leave the smallest port unchanged the velocity gets up. I would think the smallest port defines the amount of air passage. Is there someone who can explain this to me and maybe give me a clue what I can expect when I add the matching pellet probe. I do not want to install the bigger probe now as I have achieved my power target already unexpectedly with the dual transfer port only .
Please let me have your highly appreciated comments

 

[M0ist0ne]

Sounds about right. You'll gain a few fps by upgrading to the probe, but the transfer port itself provides the biggest gains as that's the main bottleneck. 

 

[dizzums]

alot of airflow characteristics are defined by port shape and the corners and path it has to traverse, not simply by size or number of ports .. a whole scientific paper could be written on influences im sure .. one simple 'dimple' in the correct location within the air path could cause the air to tumble just right and increase flow 'more than' just increasing port size, as an example ... so if you got all you need youre there lol, simple as that ..

 

[ladwict]

Thanks a lot guys. Makes sense. I read several comments re bigger transferports with the idea that if you only change/ increase the transferport it makes no sense as the probe hole is still the same hence being the bottleneck that would make the bigger transferport being useless as only so much air can pass as the smalles passage would allow for.

This seems not be the case then.... Would plenum sizes and reg setting also play a roll in this process ? I have an increased plenum ( approx. 35 cc total volume ) and work with a 135 bar reg setting. 

 

[Long_Gun_Dallas]

venturi effect. My port work on my crown got 75fps in 22, modified factory parts

 

[ladwict]

venturi effect. My port work on my crown got 75fps in 22, modified factory parts

Thanks for your reply. Did you also only change the transfer port and not the probe size/shape in order to achieve that 75fps ?

 

[triggertreat]

Yep. Don't forget the probe.

 

[qball]

At higher power/regulator pressure tune the increase from dual transfer port is more than that! All you need is 10 minutes with a dremal to gain another 10fps.


Keep in mind the consistency for pellets could be much harder to find. The smaller/older transfer port also is tuned to acted as a way to regulate speed at higher power for pellets in each caliber so if you want to shoot pellets also then it’s best to get one with a smaller pellet hole like ernest or FX TPs and flip the barrel when shooting pellets. 

 

[PappiPT]

Well, I hope it's going to work out the same on my fx crown in .177. The valve port is weird! shooting on the .30 setting doesn't have any effect, due to the small transferport. and the low setting is a lot lower because of the miniscule porthole on the powerwheel. Huma TP is on the way, can't wait now! This promises good stuff!

 

[Long_Gun_Dallas]

venturi effect. My port work on my crown got 75fps in 22, modified factory parts

Thanks for your reply. Did you also only change the transfer port and not the probe size/shape in order to achieve that 75fps ?

I did change the tanfer port hole into a large bellmouth. But I left the upper part of it alone, except to add a radius for the turn into the barrel. If I opened the whole thing up, I would have lost velocity. I cut the probe to match. I run port wheel wide open (.25-.30) 

 

[ladwict]

Nice portraits of home industry gents. Do you also agree to the fact that a bigger transferport makes the biggest difference in the TP and probe combo ? 80/20 or so ?

 

[Long_Gun_Dallas]

It should, at least on a gen 1 Crown and the impacts as well I can verify

 

[triggertreat]

The one thing that concerns me with the 8mm x 8mm DIY modified Huma porting is the amount of air it takes to fill all of this area per shot between the O-ring seals. I would much rather have a direct seal over the TP with O-rings without all of the extra space to be filled per shot. That said, I did experience a good 40 to 50 FPS increase over the OEM TP porting after all was said and done with the TP and probe mods. So, this is just all in my head, but makes good sense to me to have concerns with this. The .30 cal will now push 45gr over a 1000 FPS with a lower reg pressure, so not much concern, really. This does include a PP and a slug kit mod as well as sized projectiles to the bore (.299") using Slug A and Superior liners (700mm).