How To Make Flamethrower Exhaust - ATV Quad

By reading this you WILL learn how to make your exhaust shoot flames.


I accept no responsibility for any injuries related to replicating my system. This is for instructional purposes only. Do not try this at home. Wink wink... You will learn how to make a flamethrower exhaust using propane and a grill ignitor. A flashback arrestor would be a good addition to this setup, however I opted not to spend the money on it as there are other insurances that the flames won't travel back up the hose (detailed later in this guide). This is by far the most complete and (as far as I can tell) really the only tutorial on how to make a flaming exhaust on the web. I couldn't find any decent practical advice on how to do this, just a bunch of forum threads asking if it's possible. So here's your answer.

Things you will need:

1. Gas ball valve
2. 1/4 gas hose ~ 10'
3. Various Brass Fittings
4. Mr Heater #F273754 1/4" Male Pipe Thread
5. Battery Grill Ignitor
6. Disposable 1lbs propane cylinder
7. A decent selection of tools
8. Teflon Thread Tape
9. Balls.

I bought all of these from the local Menards store, Lowes did not have the disposable cylinder to 1/4" male adapter. I would suggest you buy these parts at your local store since they were much cheaper there than online. I just provided the links so you can see what you need to get. The brass fittings will have to be selected to fit the scenario in which you are working, I got help from a store employee who knew a lot more about brass fittings than I did. I simply told him what I needed to fit where and he took care of the rest. Expect to spend $40-$50. The biggest hitters were the sparker ($16), the gas ball valve ($8), and the cylinder-to-male adapter ($8). 

This isn't going to be the exact same process for everyone, and I have no idea how different exhausts, engines, carburetors, etc will react to this modification. It was a no-brainer for me because the ATV is old and dying anyways and I often perform mad-science experiments on it. Be careful that you don't permanently ruin your vehicle! The hole in the header pipe is irreversible (unless you weld a patch over it) and it may require you to re-jet the more finicky carbeurated engines. If you want to do this to a vehicle such as a car or truck, you'll need a 20lbs propane tank, different adapters, flashback arrestors (so your car doesn't turn into a bomb) and a little sense of adventure/death wish. The general concept here will remain unchanged no matter what you try this mod on. DO NOT TRY THIS WITHOUT THE ENGINE RUNNIG! Having exhaust gasses mixing with and carrying the propane out of the exhaust pipe is vital to prevent the flames from traveling back up into the header pipe and eventually finding their way back to your propane bottle. This could potentially cause an explosion even though propane needs oxygen to burn, and I doubt that it would ignite inside of the tank (oxygen-less environment) but I suggest you don't find out.

I'm not going to explain every tool you will need and exactly where and how to do the drills and cuts. For this reason, if you don't have enough ingenuity to understand what tools and what techniques to use to do this: don't even try it. You'll probably just kill yourself.

Use thread tape on all fittings to prevent leaks of propane gas!!!

How to:

Here's the general concept:

Setup Secured Between Handlebars (black sparker button)

The propane bottle is your fuel source (don't try MAPP gas, it doesn't work very well). The gas ball valve gives you the ability to control when the propane mixes with your exhaust. The ball valve is fitted with a barbed adapter on the out-going end to attach to some 1/4" hose that will run to your header pipe, just in front of the muffler. There, you will drill a hole and insert another brass barb fitting to accept the 1/4" pipe bringing the propane to the exhaust. The propane will mix with the exhaust gasses as they exit the muffler, and be ignited by the electric grill sparker at the exit of the muffler.




Here's the breakdown:

Disposable Cylinder to Male 1/4"

Gas Ball Valve

Brass Barb Fitting to 1/4" Hose

If you've been paying attention then you know that (as the propane gas) our journey now continues into the 1/4" hose. Where does this hose terminate? At the other brass barb fitting that is inserted into the header pipe just before the muffler. Here's the picture of that part.

Header pipe coming from the right, to muffler left. Brass barb clearly visible.

There is the potential here for the exhaust gases to heat up the barb/hose enough to melt the hose. If this become a problem for you, then get braided steel hose, or make a more elaborate joint here to diffuse the heat conduction through the brass.

Now we move on to rigging up the sparker. I suggest you stop at this point and test your rig by lighting with with a sparkler or some constant flame source rigged behind your tailpipe. I used a propane torch duct taped to a 6' stick. Once you know that your exhaust is indeed flammable, then you can proceed to lighting it by spark. Expect a flame two feet high, and a foot or so horizontal to the ground. Check the video to see an example of this rig in action so you have an idea what you're going to be getting yourself into!

You could most likely work this rig with a piezo manual ignitor, but you'd better be able to push that button really fast! The exhaust usually takes a few sparks to catch and you don't want explosive propane fumes building up while you're trying to get it lit. The battery powered models come with the insulated electrodes you'll need to effectively light this baby up and they provide a steady stream of sparks between the electrodes for as long as you hold down the button. The way you work this onto your vehicle is up to you, I can't presume to give you instructions on that. You'll need a little intuition and ingenuity to figure it out.

Sparkers Attached to Expanded Metal Exhaust Modification

Sparkers have a 3/8" Gap as Suggested by Manufacturer

The Battery Sparker is Shaded "Puke" Color, Wires connect it to Electrodes in Muffler

Now all you need to do is test your electrodes, ensure they're insulated from any grounding metal, check that there's a spark jumping between the tips reliably. You could set up the sparkers differently, say by drilling into the muffler right at the end or by welding on a couple of brackets to hold the electrodes at the end. Just be sure that wherever your spark is jumping is where the propane has had a chance to mix with the air to get oxygen. It won't ignite otherwise. So don't drill into the side of the muffler and put your electrodes in there, the propane won't ignite! Notice how my own electrode sit a few inches past the muffler's end? Also watch out that your wires are protected from the flames. That would put a quick end to your adventure.

That's all there is to it. Please comment to ask me any questions you have about making your own propane exhaust. I am not a chemist, I don't work for propane companies, I have no plumbing or gas working experience. Just a pair of balls and a workshop... oh and an old ATV to test things on! I hope you enjoyed this tutorial on how to make your own flamethrower exhaust using propane!