Please post Impact X/MKII Power Plenum .30 cal performance.

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This is all great info for those interested in custom tweaking and/or machining to wring out more power from their Impacts, but I'm not into that right now. As I mentioned when starting the thread, I was looking for actual data (physical settings and results achieved with those settings) for stock .30 cal Impacts that are either stock from the factory with the FX PP, or stock .30 cal Impacts that have had the FX PP Kit installed in the stock manner. There is a fair amount of data on the .25 cal, but .30 is really lacking.

I'm not knocking all the machining and porting info posted in this thread, as it's an incredible driving force for improvements we've seen in the Impact, but please try not to hy-jack the thread too far off topic. There are plenty of threads containing the machining and porting info, but this thread was started for other info.

Again, please don't take offense to my trying to get this back onto the original info request topic.

Thanks all!
 
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I spoke with a tech at FX USA and got the general setup guidelines they use when they install a Power Plenum kit upgrade on an Impact/X/MKII (this assumes an AMP regulator is installed... I didn't inquire about Gen 1 Impact with a pre-AMP regulator installed). Keep in mind they don't harmonically tune the guns for accuracy, but rather set them up for a generally good FPS setup condition for the specific caliber and pellet. The data the tech gave me applies to the .30 cal, shooting the JSB EXACT 44.75 gr pellets.

The tech stated the following is the GENERAL setup configuration for the .30 cal Power Plenum kit installation, but each gun can vary:

.30 cal / 44.75 gr JSB / Regulator at 100-105 bar / HSTA at ~16mm / VSA between 2nd and 3rd lines / FPS ~ 880-890 / 52mm hammer spring

At least for now, I'm not interested in shooting slugs, but only improved efficiency &/or accuracy in shooting pellets for 50 to 100 yard benchrest. For this reason, I installed my PP kit using the lighter 52mm hammer spring included with the kit. After installing the Power Plenum kit on my Impact X, I ended in the following configuration (chronographed on the bench with a MagnetoSpeed V3, but when moving outdoors, will be verified with a LabRadar):



1584541604_11149359015e722fa40d9a17.67173071.jpg




I don't know yet how it will group, but I was happy with a 10-shot group giving an ES of 3 fps. Should be a good starting place, as 870-880 has always been good for this gun.

I hope this provides others a good idea of a starting point for similar conditions.
 
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That looks really good Chuck. I know a while back there were a lot of guys trying to get the 44.75 or 50.1 JSB as fast as possible, some over 1000 FPS. Truth is, at least for pellets, the power race leads you nowhere. And anything over 950 is just outright detrimental to performance. Even if you have accuracy and precision at over about 950, you still are more susceptible to wind drift since your BC rises past that point. The sweet spot is in the 860 to 910 range for the 44.75 JSB. Honestly, the only reason for the big power mods is to shoot heavier slugs faster…

Edit: above where I said rises I meant lowers above 950 FPS.


 
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That looks really good Chuck. I know a while back there were a lot of guys trying to get the 44.75 or 50.1 JSB as fast as possible, some over 1000 FPS. Truth is, at least for pellets, the power race leads you nowhere. And anything over 950 is just outright detrimental to performance. Even if you have accuracy and precision at over about 950, you still are more susceptible to wind drift since your BC rises past that point. The sweet spot is in the 860 to 910 range for the 44.75 JSB. Honestly, the only reason for the big power mods is to shoot heavier slugs faster…
Click to expand...

Helps with efficiency also as ive shown. So not really the "only reason".
 
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That looks really good Chuck. I know a while back there were a lot of guys trying to get the 44.75 or 50.1 JSB as fast as possible, some over 1000 FPS. Truth is, at least for pellets, the power race leads you nowhere. And anything over 950 is just outright detrimental to performance. Even if you have accuracy and precision at over about 950, you still are more susceptible to wind drift since your BC rises past that point. The sweet spot is in the 860 to 910 range for the 44.75 JSB. Honestly, the only reason for the big power mods is to shoot heavier slugs faster…
Click to expand...


Thank, CC. I agree on the power need for shooting pellets. I have never believed higher velocity always equates to higher accuracy. I did try the original 57mm hammer spring in the PP install initially, but I felt it was more power, plus higher wear & tear than I wanted if I wasn't going to be shooting slugs in the near future. I also figured the lighter hitting hammer spring might help with the harmonics and accuracy. As a reference for comparison, here is what I experienced (all things being equal except hammer spring):

Regulator: 111 bar / HSTA: 17.16 mm / VSA: at 4th line, with Notch #1 (smallest) at 3:00 when knob is viewed from muzzle end of gun / JSB 44.75 gr

57mm (original) hammer spring: 919 fps

52mm (new) hammer spring: 729 fps

These were just spot chronograph readings off a labradar, and not a series average.


 
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So has anyone added a polish power plenum to a mk2 pp gun? It seems the lower reg pressure helps with the harmonics of the gun. I’m considering the 357impact and wondering if the polish power plenum would be a worthwhile upgrade, probably use it for varmints.
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The Polish version is about 16-17cc larger in volume so yes it will help in .30 caliber and larger. You could also add an external for a boost in 357 but you will reach a point where valve size and porting are holding you back.

The plenum from Poland costs about $150 shipped UPS and fits MKI and MKII. Don't listen to anyone telling you the price is higher or they have exclusive import rights because it's not true. I just confirmed this with the manufacturer and proved it to the forum owner. If you email him give him a few days to respond because he's busy.


AT Michał Osyda


98-300 Gaszyn, ul.Źródlana 13a

Tel. 883999733



http://www.airguntuning.pl


 
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Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
 
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Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
Click to expand...

The power difference because of different hammer springs. The new valve adjuster can be opened all the way just before the oring. The 4 groves are not relevant anymore. Some people still think the 4th line is the maximum they can get from the valve adjuster. It could be true in older impact's without power plenum, but all newer impact with power plenum or new valving have a spring. 
 
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Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
Click to expand...


What is the OD of the power plenum?
 
Upvote 0
Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
Click to expand...


What is the OD of the power plenum?
Click to expand...

Haven't measured it yet Nathan (I'm also not at home right now) but looking at the pictures, the Polish plenum sits flush with the magazine plate underneath the breech block, exactly like it is the case with the FX PP.
That makes me wonder if there really is a 17cc difference in between both plenums like the rumors say. 

Just watched the video about the install of the Polish plenum, and there is a collar which needs to be mounted on the original valve housing, it looks a lot bigger than the original FX valve housing collar. If that is the case, it also takes away some volume from the plenum chamber.

But again, I'm just speculating and judging from pictures, I haven't taken any real life measurements yet :)
 
Upvote 0
Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
Click to expand...


What is the OD of the power plenum?
Click to expand...

Haven't measured it yet Nathan (I'm also not at home right now) but looking at the pictures, the Polish plenum sits flush with the magazine plate underneath the breech block, exactly like it is the case with the FX PP.
That makes me wonder if there really is a 17cc difference in between both plenums like the rumors say. 

Just watched the video about the install of the Polish plenum, and there is a collar which needs to be mounted on the original valve housing, it looks a lot bigger than the original FX valve housing collar. If that is the case, it also takes away some volume from the plenum chamber.

But again, I'm just speculating and judging from pictures, I haven't taken any real life measurements yet :)
Click to expand...

I think that collar is only used pre impact mk2. I didnt use it on mine and it wasnt included after i told Michal i needed a plenum for mk2.
 
Upvote 0
Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
Click to expand...

The power difference because of different hammer springs. The new valve adjuster can be opened all the way just before the oring. The 4 groves are not relevant anymore. Some people still think the 4th line is the maximum they can get from the valve adjuster. It could be true in older impact's without power plenum, but all newer impact with power plenum or new valving have a spring.
Click to expand...

Here you can see the difference in valve housing between the PP valve housing (left) and the Impact X valve housing with separate valve seat (right).

The PP valve seat sits way deeper than the old style valve seat, creating sort of a 10.5mm tunnel around the outer diameter of the valve poppet, which (IMHO) reduces flow.

I found out that the speed of my gun had decreased when I installed my upgraded valve stem with PEEK poppet, which I made 0.3mm bigger in diameter than the stock valve......

When I turned down the OD of the PEEK valve a bit, the speed increased again to the stock value.

The old valve sits way higher, and the slots go all the way to the beginning of the valve seat, which means it is not in a tunnel like the PP valve housing. (Read: less restrictive)

I hope my story is clear (it is difficult to explain), but when you check the photo below, you will know what I mean :)



1584670320_10041843045e7426706e7e09.09762012.jpg

 
Upvote 0
Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...

I keep on wondering about that too......... The outer dimensions look identical, so I can't really point where the claimed extra 17cc is coming from........

One of the reasons that the Polish plenum is said to be more powerful could be that it uses the "old" valve housing, which looks to be less restrictive than the original PP valve housing.

That's also the main reason why I have decided to make a new valve housing for the original power plenum, and I am getting some very good numbers in 22 cal.

(fyi https://www.airgunnation.com/topic/pp-valve-housing-2-0/ )
Click to expand...


What is the OD of the power plenum?
Click to expand...

Haven't measured it yet Nathan (I'm also not at home right now) but looking at the pictures, the Polish plenum sits flush with the magazine plate underneath the breech block, exactly like it is the case with the FX PP.
That makes me wonder if there really is a 17cc difference in between both plenums like the rumors say. 

Just watched the video about the install of the Polish plenum, and there is a collar which needs to be mounted on the original valve housing, it looks a lot bigger than the original FX valve housing collar. If that is the case, it also takes away some volume from the plenum chamber.

But again, I'm just speculating and judging from pictures, I haven't taken any real life measurements yet :)
Click to expand...

I think that collar is only used pre impact mk2. I didnt use it on mine and it wasnt included after i told Michal i needed a plenum for mk2.
Click to expand...

Copy that, thanks for the heads up :)

I haven't seen a Polish plenum in real life, so I still can't say if my approach is true. (Just crushing my virtual 3D model brains on this one LOL) 

I'll measure the OD of the PP when I have the chance, and post it here :) 

Cheers, G
 
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I might be mistaken, its been a while since I installed it so I may be wrong. I got roughly 33mm as the OD on the Polish plenum.
Click to expand...

It actually doesn't matter much, as we apparently have a poopload of power available on tap with both designs ;)

Happy days, I'm really enjoying my Impact as a tuning platform again. Lost a bit of interest in AG's due to the ELR shooting thing, but now it all came back again.

Would love to see a Polish plenum in real life, but they are not around in big numbers where I live.


 
Upvote 0
Heavy-impact, have you measured both plenums? I had both plenums and I think they are the same size so I sold the the polish plenum and kept the fx one as I think it has way better build quality.
Click to expand...


I just took the manufacturer's word's on it. FX advertises 53-54cc 

Michal Osyda says...

"I can make that plenum for you. Volume of that has exactly 3 times larger capacity than original mk2 plenum (near 70ccm3)"
Click to expand...


 
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