Nee HPA install - inconsistent output

[Gunboat Diplomat]

Any help welcome and appreciated on this one.
 

Just completed (well, assembled) a new HPA build using an Inferno Gen2 on my boneyard Specna M4. 
 

I’m getting inconsistent output shot to shot. 
 

On semi, each shot is very weak with an audibly weak output (think mouse fart), often failing to fire completely or posting very low sub 100 fps. 
 

On quick double taps of semi, the second shot is much stronger. 
 

And on full auto, output is audibly more consistent shot to shot. 

Have tried output pressure between 90-110psi with no observable change in behaviour.  Reg pressure gauge cycles as expected with each shot. 
 

Splitting the lower shows it’s nothing barrel or hop related. 
 

Will post a vid to demonstrate shortly. 

https://youtube.com/shorts/Rv-CdfinMqk?si=EQp79Y1U4V8hxUiB

 

[ButcherBill]

That's an easy fix.

I do that when I'm constipated... your HPA needs to poop.

 

[Impulse]

Have you tried increasing the dwell? It might be that the dwell is too low so you're horrendously undervoluming. I had similar issues with my MTW 308 and that solved it for me.

 

[Gunboat Diplomat]

Have you tried increasing the dwell? It might be that the dwell is too low so you're horrendously undervoluming. I had similar issues with my MTW 308 and that solved it for me.

Must admit I’ve not adjusted dwell yet from factory defaults. Didn’t consider it would make a difference since the engine is under powering even out of the barrel. 
 

Good shout though, will give it a try and see if it changes anything. 

 

[Gunboat Diplomat]

I’m a nob. Bad lipo, one of the cells is dead. Didn’t have enough power to cycle the solenoid. 
 

Fresh battery - all good.