[SiliconeSword]

So back in 2018 or 2019 I made an HPA engine for my old Double Bell VSR-10 and quite liked it, but eventually I got a Wolverine BOLT in a separate gun and the homemade engine broke not long after.
The cause was I didn't use any glue to affix a gasket into a little piston and the gasket came out, and since I pressed and glued the engine together there was no fixing it.
The second failure was the trigger valve, I assume because I didn't know about oils back then and had used WD-40 on the O-rings.
Excuse the terrible camera quality, this was an extremely bad phone.

Fast forward to 2 weeks ago, where I made this here GEN2 engine

Sensitive content, not recommended for those under 18

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So the major improvements
Not inside of a cylinder, replaces the cylinder
Better nozzle geometry
COMPLETELY DISASSEMBLES
Better refresh rate
Lower volume (more controllable power)
Better trigger valve
More simple
Cooler looking

So this system is a QEV (Quick Exhaust Valve) with a 2/3 (2 position 3 way) normally open trigger and can output probably 4J with a good length barrel and heavy BBs, and will do so with good FPS consistency.
Not really much else to say except that I'll be putting it in my current ultra custom VSR-10 and selling it once I am pleased with how it shoots, so look forward to that upcoming post if you are interested.

Also, here's a blank firing demonstration

Another thing, you guys are completely allowed to make these if you so desire, but you need an understanding of airguns and air systems.
Still, 13-14 year old me was able to build my first one which lasted 30K shots or so, so it's not rocket science.
For better information on these, look of QEV airgun and QEV pen gun/flashlight gun and maybe try building one of those first as they aren't so hard.

 

[BlackDogAirsoft]

Nice. Might be a future project.

 

[SiliconeSword]

Didn't realize the 18+ thing, stupid bots

 

[mrvanagas]

Didn't realize the 18+ thing, stupid bots

Cause thats too damn sexy for anyone under 18

 

[Dimitri MdP]

That's so awesome. Gotta admit it makes a funny noise though

 

[wyz2285]

You can easily get 5 plus Joules with a piston valve setup like this if the piston is well made.
Downside is the exhausted air. But the valve is normally way more efficient than a simple solenoid and makes up for it.

 

[SiliconeSword]

That's so awesome. Gotta admit it makes a funny noise though

The noise is less noticable when it's in a gun, but it's certainly annoying lol.
It's kinda like hearing someone shooting a PTW and you're totally confused for a bit.
I bet that if I make another piston that's tighter or something then it won't make that noise, but it's not very urgent.

You can easily get 5 plus Joules with a piston valve setup like this if the piston is well made.
Downside is the exhausted air. But the valve is normally way more efficient than a simple solenoid and makes up for it.

My old engine once stuck a .36g BB into a piece of wood when my shitty Redline SFR pressure crept, and that's with a 313X6.01 barrel and a terrible air seal (an AEG bucking inside of an AA chamber because some dipshit said it's good) and I wasn't able to get even a .48g to stick into that piece of wood a few years later even with 3.6J, so that must have been some serious power.
That engine had an air volume that was extremely oversize, so I made this newer one smaller to make it more efficient.
Also seeing as this one is able to be disassembled, you can put plastic or metal discs on the small tube inside, taking up volume and reducing wasted air.
You only want to add spacers until you drop in FPS as you probably know, as then you'd just have to turn up the PSI and then you'd be slightly less efficient.

That's because the higher the PSI the more air comes out of the trigger valve to fire the piston, as the air is more compact.
But yeah, if you lower the PSI and maximize the volume then you will waste less air to fire the piston, and you can tune the volume that goes out the barrel with the before mentioned volume adjusters.