QEV modding

[Daltonultra]

Well, I found a spring I think will work right for my QEV, now I just need to know what size hole I need to drill through the piston to allow it to pressurize from the chamber side without rendering it unfireable.

It's a 1/2" QEV from Fastenal

[Lentamentalisk]

Just start with a tinsy hole, and move up from there if it doesn't work fast enough for you.

[jackssmirkingrevenge]

Essentially the important thing is that the rate of flow past the piston is lower than the rate of flow through your pilot.

[Eddbot]

while we're on the subject, i've got a QEV like this, when filled from the pilot, the air slips past on the slanted edges



if i turned it around like this, and added a spring, would i even need to put a hole in the piston to fill from the chamber?

[psycix]

if i turned it around like this, and added a spring, would i even need to put a hole in the piston to fill from the chamber?

No edd, but it would let alot of air through on pilotting.

Dalton, I would start with the smallest hole possible. Like a needle.
Maybe you should PM brian the brain.
He is the one who knows most about this.

[Daltonultra]

if i turned it around like this, and added a spring, would i even need to put a hole in the piston to fill from the chamber?

No edd, but it would let alot of air through on pilotting.

I think it would also tear up the edges of the piston really badly. That is exactly how mine looks inside, and there is a plastic sealing ring inside the top. If I reversed the piston like Edd suggests, the edge of the piston would hit that ring, and over time it would shred it.

Dalton, I would start with the smallest hole possible. Like a needle.
Maybe you should PM brian the brain.
He is the one who knows most about this.

I'll do that. Failing his reply, I'll start at 1/32". I believe I have one in my model drill kit.

[biged]

I have made replacement rubber pistons for these valves.
I used a piece of 1/4" rubber and cut it the same diameter. Beveled the edges slightly. Drilled two 1/16th inch holes on either side, with a groove cut across the bottom on the pilot side. Works lightning fast even at pressures up to 250 psi. Has only a minimum bleed through on the pilot with the groove cut.



If you do not get the new rubber piston just rite, it will turn on, but not turn off at higher pressures. Took several attempts to get it rite.

I use it as a relay valve for a bb flamethrower.
http://i70.photobucket.com/albums/i110/ ... ower_7.jpg

///ed///

[Daltonultra]

That's a great idea, I may have to try that before I go drilling the factory piston...

[psycix]

The factory pistons can be bought separately. They cost just a few bucks.
So dont freak out if you think you've destroyed your QEV.

[Daltonultra]

I can make new ones out of a hockey puck anyways. $1.05 a hockey puck and twenty minutes in the garage gets me two pistons, I figure.