Homemade Flame Exhaust Kit
In the 1950s, exhaust flamethrowers were all the rage on the custom street scene but went out of fashion some time in the 1970s. Credit for their recent resurrection could be attributed to nostalgia or to certain flame-spewing street racing movies, but either way the big burn is back. Modern fuel-injected cars will require a little more creative approach to flaming than old school carbureted rides, but the basic principles remain the same.
The primary difference between modern flamethrower setups and carbureted ones is the source of fuel. A flamethrower relies on a steady source of unburnt fuel, and this was once accomplished simply by turning off the engine’s ignition coil and allowing spent gases to pass through the engine. These gases would then be ignited by a tailpipe mounted spark plug and WHOOSH…massive flames.
Modern fuel-injected engines are programmed to stop injecting fuel when the ignition is cut, so the old approach isn’t going to work. Aside from that, any catalytic converter is going to converter most of that unburned fuel into other chemicals, so old-school setups on modern cars are double-doomed from the start.
Triggering your system is simple. Install a spark plug into your tailpipe 3 to 6 inches from the tip, and trigger it with an ignition coil from a 1985 ford F-150. Trigger your coil by splicing into the engine’s ignition coil, and use a three-position switch to alternate between the two circuits.
Fueling the Fire
There are a number of different solutions to the problem, and they all involve injecting fuel into your tailpipe. One of the more popular approaches is to use propane injection, which is cheap and easy to install. Propane injection requires a pressurized tank, an activation solenoid like those used on nitrous setups and an injection line. Propane setups will yield a 5- to 6-foot plume of bright yellow flame.
If you want a huge dragon tail of 20-foot flames or those bright blue afterburners from the movies, you’re going to have to inject fuel. Most people use a a large fuel injector plumbed into the car’s fuel system (activated with a simple 12-volt switch), which works well. Bear in mind that you’re going to want to inject the fuel after the mufflers, or you risk turning your car’s silencers into a bomb.
An alternative to using the car’s fuel system is to use a dedicated fuel pump drawing from its own tank, which gives you the option of varying the fuel mix to produce different colors and effects. For instance, adding alcohol will make for a more transparent blue flame, adding some boric acid will yield an otherworldly green blaze, and the material from a road flare will burn a bright crimson.
To trigger your flames, rev the engine up to between 4,000 and 7,000 RPM, and quickly flick your switch from the “engine” position to the “flamethrower” position. Put your switch back into the “engine” position before the car drops below 1,000 RPM to prevent stalling.