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I have been searching over the past week or so trying to educate myself as much as possible before going ahead and trying to build an exhaust flame kit from scratch (the ones on sale on the internet are ridiculously overpriced for essentially and some assorted electronics).

I have a Honda CBR (motorbike) and I want to split the fuel line with a small electric fuel pump and a NOS fogger in the exhaust. Have a separate fuel supply (probably a propane canister) with a solenoid valve and a spark (plug + coil).

My question is - does anyone know of any good documentation on creating/installing these kinds of set ups?

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    Please don't put a flame thrower on your CBR, it will make my CBR cry ( tears of shame ).
    – Scott Hillson
    May 8, 2013 at 18:23
  • It's cool in moderation :)
    – Bill
    May 9, 2013 at 8:56

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A quick google search got me to here:

http://www.rs25.com/forums/f105/t41589-diy-flame-thrower-exhaust.html

It's got pretty good diagrams for the electrical part, I haven't gone through the whole document myself though. I imagine you'd want to adapt this guide to your needs and maybe read other ways people do flamethrowers, i.e. google for "diy flamethrower".

There are also people selling instructions on how to do this on ebay (that's how the person got the info above in the first place). Here's one link, for example:

http://www.ebay.com/itm/FlameThrower-Exhaust-Single-and-Duel-/110952173786?pt=Motors_Car_Truck_Parts_Accessories&hash=item19d543d0da&vxp=mtr

These are quite cheap, so maybe spending ten bucks on something like this would be worth it.

If you think you have the fuel part covered (e.g. a pressured propane tank and a 12V activated valve, for example --- btw the pressured propane tank sounds very dangerous in case of an accident) then the electric circuit you'd need is like this:

mod to the wiring diagram for flamethrower

You'll have to figure out a good relay valve to use with propane, something like this might work.

Also, let me say that, in my humble opinion, nobody should be doing this, so if you do, please make sure you're not putting anyone else in danger. In particular, I would not drive with a pressurized propane tank attached to my car anytime there's a possibility of mechanical damage.

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  • That's pretty good :) I couldn't find anything this good.. But as there's a bounty, I'll accept if you can give me a similar link for motorbikes? ;)
    – Bill
    May 14, 2013 at 23:48
  • I don't see why doing this on a motorcycle would be any different. All of the kits I found that you can buy online are for both cars and bikes, and I'd be really surprised if the instructions differed significantly between the two. The real problem with the link I gave is that it interrupts the spark to the engine such that the fuel mixture doesn't burn until it comes out the exhaust. This means you can't really ride and shoot flames at the same time, and you engine might stall.
    – vlsd
    May 15, 2013 at 17:49
  • Yeah I need a kit that doesn't wire into the spark to the engine - a standalone spark unit if you will. Do you think it would be enough to simply not wire it up?
    – Bill
    May 15, 2013 at 23:07
  • I don't think the spark is the problem, the battery should be ok handling one extra spark plug. The problem is, in order for the exhaust to be flammable you'd have to stop the combustion in the engine, which is never ideal. I would have a separate circuit to create a spark and then a way to deliver pressurized fuel to where you want the flames to come out. You could use a propane tank, or patch into your fuel system (past the fuel pump) and then have a relay operated valve to only let the fuel out when you want flames.
    – vlsd
    May 16, 2013 at 14:36
  • I want to have a separate propane tank (I did specify this, possibly badly, sorry) because flushing petrol through the engine will ruin my cat and exhaust and will generally damage my bike, and it's much harder to remove (for MOT etc.). I am going to mount a Prop canister and have a solenoid valve hooked up, All I want is a kit that essentially is a pre-assembled coil and whatever makes the spark (this is where I reckon my DIY would no longer be good enough)
    – Bill
    May 16, 2013 at 17:09
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Most people that do this tend to keep their methods secret. I have seen it done at carshows,races etc and from the smell I can tell you they aren't burning gasoline. The issue with using fuel from you tank is these things burn large amounts of fuel and you have a relatively small tank that is fairly close to you body. Any malfunction or miscalculation could be deadly. At the least you may consider getting the installation instructions from a commercially available kit so you'll be aware of some of the safety factors built into the system.

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  • Yes some people use NOS or Propane, among other things (sometimes a dedicated fuel tank with special fuel mixes), usually for coloured flames (blue flames are awesome!). Using a propane system would remove some of the dangerous elements of it and I will think about doing this. Thanks for your input
    – Bill
    May 8, 2013 at 8:56
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A few years back, I saw a show where they installed flame throwers on a car. They used a system that would kill the spark on the engine (can't remember if they killed spark entirely, switched on/off, half the cylinders, etc.) sending raw air fuel mixture through the exhaust, then ignite it with a coil and spark plug in the exhaust. Might be able to rig something up with a relay to send the coil signal to the engine coil (normally) or tail pile coil(for flames). Rev it up and hit the button, when the RPMs drop, release, let it rev up again and hit it again. This would require the least amount of modification, as you would not need a secondary fuel supply, pump, nozzle, valve. Running unburnt fuel through your exhaust isn't great, but shouldn't be a big deal overall. Might want to change the oil a bit more often. Also, this will not work of you have a cat.

As I'm writing this, I'm thinking there is going to be a perfect air fuel mixture through your entire exhaust system, so I'm not sure what kept the entire thing from exploding...

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