Velocity all over the place on Illusion

[Drachen]

Got a new to me illusion in. Tried it out yesterday for the first time. In the morning the velocity was a little bit spiky but I chrono'd low and it wasn't a big deal. Never going above 290 and only went as low as 275.

Afternoon comes around and I'm shooting about 310-320 (chrono for pumps at this field is 300).

I try to adjust it back down and it doesn't matter if I adjust the reg, or the screw on the front I'm either consistently 215-230 or 330+. There was no middle ground. The faster I shot the higher the velocity went.

I'm not super sure how to tune these. It's been years since I've messed with one. I plan to get a reg tester, but I don't even know what the reg should be set to, or if that reg is shot.

I have flyweight Nate's valve in it, and the azodin rock hpr. Does anybody have a tuning guide for the illusion?

[Jonnydread]

In my experience Illusions are a bit trickier to tune than pump cockers. They use a choke screw to adjust velocity vs. spring tension, which can be a bit finicky and more challenging to balance.

Firstly, are you sure you weren't getting rollouts or partials? That will eff up your velocity numbers significantly.

Second, stock Illusions usually use fairly high pressure. You mentioned you have Nate's valve, but what about the valve pin? I recall the modded valve pin (may have been from a Diadem?) helped increase consistency with the new valve at a lower pressure. You should be able to get it to a point where you can use the choke screw OR the HPR to adjust velocity, but I would try to avoid re-balancing both.

flyweightnate may have some more insights for you

EDIT: not actually a choke screw, it’s actually adjusting valve spring tension. See Gabe’s post below

[flyweightnate]

... The faster I shot the higher the velocity went.

I'm not super sure how to tune these. It's been years since I've messed with one. I plan to get a reg tester, but I don't even know what the reg should be set to, or if that reg is shot.

I have flyweight Nate's valve in it, and the azodin rock hpr. Does anybody have a tuning guide for the illusion?

That first quoted sentence above is super interesting - it sounds like reg shoot down increased velocity!

I know very little about the Azodin regs, but if it were me, I'd be rebuilding it right away with a light coating of grease, and looking for scoring around the piston.

If the valve is what's causing issues, 450-550 psi always worked best on my Sentinel; I might need to double check my Illusion pressures abs let you know what I'm running.

[gabe]

In my experience Illusions are a bit trickier to tune than pump cockers. They use a choke screw to adjust velocity vs. spring tension, which can be a bit finicky and more challenging to balance.

Second, stock Illusions usually use fairly high pressure. You mentioned you have Nate's valve, but what about the valve pin? I recall the modded valve pin (may have been from a Diadem?) helped increase consistency with the new valve at a lower pressure. You should be able to get it to a point where you can use the choke screw OR the HPR to adjust velocity, but I would try to avoid re-balancing both.

flyweightnate may have some more insights for you

Not actually a choke screw, they just have a screw that adjusts tension on the valve spring instead of the hammer spring like most guns. Turning it out lowers valve spring tension and raises velocity. Another cool side effect is that the valve spring guide acts as a stop for the valve so it only opens as far as the adjuster allows. If you turn the adjuster inwards it not only increases valve spring tension but also limits valve opening causing velocity to fall.

I ended up using the Diadem valve stem which helps a lot. My baseline was to screw the front adjuster in until you can no longer hear the hammer hitting the face of the valve. It'll sound like a softer "thud" instead of a "chunk" sound. This is the lowest tension you would run with high pressure. Now go another full turn out and leave the front adjuster. Run the reg up until you get field velocity. If you can't fine tune with the reg without getting big jumps then something is wrong with the reg. The valvetrain adjustment is pretty much set and forget and you go off the reg for velocity.

Chances are good you're in the "sweetspot" but as there isn't one for a gun adjusted off the valve spring you're just on the edge of getting great long dwell and running low pressure and having enough pressure to snap the valve closed. You need to go further out with the valve spring (honestly you can just run it all the way out and be fine) and then just turn the pressure up until it works. It's not a very good low pressure setup; you're just making the valve hang open a long time and running less pressure. The Illusion was really designed around high pressure.

[Jonnydread]

Thanks for the correction, just had a peep at the manual and you’re spot on.

[rathbaster]

The Illusion was really designed around high pressure.

And CO2 (which is of course high pressure)

I owned one when they first came out and ran it stock class, 12 grams and a stock class feed all the time (I never see the stock class feed come up for sale...I know others had them at the time)
When I did put a hopper on it (once) I continued to run it on unregulated CO2 and it ran fine

[Cunha]

Seems like hpr may be too high.

the valve you had should work on good low pressure.