Fuel-Injection Method

[Spudinator]

I recently discovered a great way to fuel minis, I think you guys will like it. You dont have to worry about getting a good fuel mixture, and if you do it right you dont even have to vent the chamber. It uses the Venturi system from a mini-torch, like the ones you find in gas stations (not a regular lighter, the ones that have a hot blue flame). The parts you'll need for it are the torch, a long-stem lighter (for the fuel canister and tubing), and a few small screwdrivers to disassemble the lighter.


First off, you need to seperate the venturi (just so you know, the end of the venturi is where the flame comes out) from the body and fuel canister of the lighter. Most mini-torches have a small phillips screw at the bottom, this usually will allow most of the lighter to come apart.

From there, seperate the butane canister from the venturi (usually connected by a small rubber hose), then unscrew the venturi from the torch body. If you did it right, you should have what is showing in the pic labeled "Venturi".

To use it in a gun, you'll need to drill a hole just a bit smaller than the threads in the chamber (Pill bottles will do great with these), then use a small wire stuck in the end of the venturi to guide it into that hole from the inside of the chamber. When you have it through, use a pair of pliers to twist the threads in from the outside. Connect the fuel hose to the small barb at the bottom of the venturi, and thats it.

Make sure the chamber isn't sealed when you inject fuel, the back pressure prevents the venturi from injecting the correct fuel:air ratio.



Any Questions? Comments?

[jackssmirkingrevenge]

Since ratio is so critical on a smaller scale, how do you calculate the volume you're injecting?

[f.c]

i think it would work. though id be more likely to just use my propane torch. and yes i have made a propane powered mini

[jimmy101]

Jacksmirk..., I believe what Spudinator is going for is to not have to calculate anything at all.

The venturi supplies an air + fuel mixture in the correct ratio. To use, you need to flush the chamber several times with the gas mix this produces. Or, install it on one end of the chamber, open the other, and just flush fuel mix through for a while. Not exactly fuel efficient but in a mini it really wouldn't matter much.

Like f.c. said, the same thin has been done with a standard Benzomatic torch head. A torch head, and this "venturi" are both the same thing as a Bunsen Burner, which should also work.

I've always wondered if the gas flow through the nozzle is dependent on the thing actually being lit. Does a Benzomatic torch suck as much air in through it's vents when the flame is not lit as it does when it is lit?

[jackssmirkingrevenge]

*blink*

I completely missed the "venturi" bit.

I need to get away from this PC

[Spudinator]

Jimmy~ You are correct, once you fire you can either blow into the chamber to vent it then inject fuel, or simply inject fuel after firing, but you have to run the venturi for a bit longer.

The entire reason I posted this was so you don't have to use a propane torch, they are way to bulky and incovenient to use in a mini (although I do swear by them with large combustions). With the venturi system, you can have the fuel cansister and everything onboard the gun, which would make it much more convenient to use, you simply have to push that little lever on the butane canister (or, like I am doing, rig up a system that loads a BB, vents the chamber, and fuels it all at the same time) to fuel your mini.

I can probably get several hundred shots out of one of those butane canisters (and they are refillable too, you unscrew the adjustment lever out a ways so it flows fast, then stick the butane refill canister over the brass barb and push it up with the lever), so I dont think efficiency is a big issue here either.

You guys should try it out, it really is a great fueling system. I'd like to see how other people like it...

[jimmy101]

Spudinator: How many chamber volumes do you think you need to flush through to get a reasonably complete fueling?

Best case scenario would say one chamber volume would only give you 50% fueling. Two chamber volumes 75%...

Ten chamber volumes would certainly give you ~100% but that is a heck of a lot of waste.

[Hubb]

I just built and posted a mini that operates with butane. It hasn't misfired but I have gotten inconsistent shots with it. This seems like a good idea for me to use, since it will ratio the fuel properly (luckily I saved this little piece when I disassembled the lighter).

Thanks for this info.

[Spudinator]

Jimmy~ Really, all you have to do is give it a couple seconds to run, as long as there is a vent port (the barrel will do as long as its a decent diam, think 3/8+) to eliminate backpressure. If you set the venturi up so that the gases flow around the chamber a bit, say like the port of a vortex BB gun, it fills the chamber rather thoroughly. The gun I have been using this on has a somewhat small chamber, 1.5" x 2", so it may take a tad longer for larger chambers, but not by much. I think you'd be surprised by how much gas comes out of it, especially if you turn the flow rate up on the butane canister.


Hubb017~ In the beginning I also got inconsistent shots, I fixed the problem by increasing the vent size and giving it a bit of a longer fueling, try that and see if it fixes the problem.

[SpudBlaster15]

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[Spudinator]

Uhh, how are you correlating my post with Mr Douche? I posted this for mini spudguns (I'm pretty sure you arent going to find ball valves, regulators, and fittings to make a metered propane system for a mini heh), and I'm not an asshole like Affliction. I'm not sure if many know this, but I was one of the mods on Spudtech for some time, so I HATE assholes/douchebags/Afflictions...



Anybody else tried the system?

[frankrede]

Uhh, how are you correlating my post with Mr Douche? I posted this for mini spudguns (I'm pretty sure you arent going to find ball valves, regulators, and fittings to make a metered propane system for a mini heh), and I'm not an asshole like Affliction. I'm not sure if many know this, but I was one of the mods on Spudtech for some time, so I HATE assholes/douchebags/Afflictions...



Anybody else tried the system?

I haven't tried it, but its something I plan to try soon.


And don't worry, you are in no way like affliction.
Affliction said his system was better and denounced all other systems.