P90 PolarStar Fusion Engine Conversion

The P90 gun is very compact bull-pup design that has a very futuristic look. Since the gun is so compact, it is popular on CQB fields, but can also be used effectively on outdoor fields as well. To take the gun to the next level of performance, it would seem that adding it to the PolarStar Fusion Engine family is the next step. Todd Malan wanted to be the owner the highest performing, fully loaded P90 airsoft gun available, so he sent it out to have a Fusion Engine installed. After a couple fits and starts, I was able to make the Fusion Engine work in the P90 without the complication of a “Z” nozzle and still maintain the ability to port the Fusion Engine to other V2 gearbox guns in the future if desired.

There are two key challenges to fit the Fusion Engine in the P90 platform. First, the P90 uses a V6 gearbox with an offset nozzle. Similar to the F2000 gun, the nozzle is offset toward the top of the gearbox, but the P90 body is much smaller than the F2000, so aligning the Fusion Engine so a straight nozzle was a bit more difficult. Second, the P90 airsoft body is one piece, or rather it is two halves factory glued together, and separating the two halves results in a high risk of destroying the body. So installing the Fusion Engine into a body where you can’t easily modify or examine the internals of the box is very difficult.

Fortunately, I was able to acquire a boneyard P90 body that was already cleanly split in half (thanks to Rob Sollars of OpposingForce Airsoft). I could then determine the best placement for the Fusion Engine and other parts by test fitting them against one half of the P90 body. I initially devised an installation plan based on fitting the Fusion Engine against one half of the P90 body, so I attempted to follow this pattern on Todd Malan’s P90. Unfortunately in my attempts to split the glued P90 body, I managed to warp the body (note, boiling a plastic body to try and break glue bonds does not work, it merely allows you to easily twist the body into a mangled mess). Todd was understanding enough on this misstep to allow me to replace the body of his P90 with a new one, and this provided me opportunity to find a new way to install the Fusion Engine without splitting the body. I was able to work out an install plan on the split P90 body, knowing the final install would be on a single piece body.

I wanted to avoid using a “Z” nozzle in the P90 conversion. The nozzle offset is not as large as the M14 nozzle, so it would be very difficult to make a “Z” nozzle (with my modest equipment) where the nozzles would overlap. The Fusion Engine would need to be shifted up to make sure the nozzle would align with the hopup, but there is basically no headroom in the P90 body. The AEG gearbox rests against the top of the body shell. After some careful measuring it was apparent that the Fusion Engine cylinder would fit by milling down the top of the cylinder, allowing it to be shifted up enough to match the nozzle and hopup.

I milled down the Fusion Engine front cylinder and back cylinder. The middle (poppet) cylinder needs to remain intact to protect the large sealing o-ring. If this cylinder is milled down, the o-ring is exposed and the integrity of the air seal is compromised. To accommodate the unmodified middle cylinder, a small clearance window had to be cut into the P90 body. The Fusion Engine cylinder assembly can then be locked into place using a screw from the top, and supported at the back using the existing AEG gearbox support plate.

The P90 uses the same trigger, safe, semi-auto and full-auto mechanism as the F2000. It has a metal push rod loop to activate the trigger on the AEG gearbox. Microswitches were used to provide the trigger and full-auto fire functionality.

The stock nozzle was milled down to match the stock P90 AEG nozzle, and a small custom circuit board was used to replace the large stock trigger circuit board of the Fusion Engine.

With the single body shell, the microswitch mount locations could be drilled from the outside and mounted on the inside using the bottom access plate and Fusion Engine could be installed from the back, just like the AEG gearbox.

Todd dressed his P90 up with a tri-rail, high powered flashlight, extended inner barrel, suppressor, box mag and hi-cap magazine. With the rapid fire capabilities of the Fusion Engine, the P90 box mag becomes an ideal addition to the P90. This PolarStar Fusion Engine powered P90 is now a very fearsome airsoft gun on both CQB and field games.

 UPDATE 10/30/2012
Here’s a video review of one of my Fusion Engine P90 conversions:

Happy Airsofting,

– Rudy