Making your car shoot flames, often called an "afterfire," primarily involves modifying the exhaust system to allow unburnt fuel to ignite outside the engine. The most common methods involve tuning the engine to run rich (excess fuel) and installing an anti-lag system or a spark plug in the exhaust tip. However, this practice is extremely dangerous, can cause severe damage to your engine and exhaust components, and is almost always illegal for street use due to emissions and safety laws. It should only be attempted by professionals in a controlled, off-road environment like a race track.
The principle is straightforward: you need to get fuel into the hot exhaust system where it can combust. On turbocharged cars, an anti-lag system (ALS) is often used in rally racing. It keeps the throttle open and retards ignition timing, forcing a fuel-air mixture into the hot exhaust manifold to keep the turbocharger spooled up between gear shifts, resulting in loud bangs and flames. For naturally aspirated engines, a "2-step rev limiter" can achieve a similar effect by altering the ignition cut at a preset RPM, causing fuel to dump into the exhaust.
Another method involves installing a secondary spark plug in the exhaust pipe, often connected to a switch or controller. This plug directly ignites the unburned fuel. Regardless of the method, running the engine this repetitively rich washes oil off cylinder walls, increasing engine wear, and can destroy catalytic converters and oxygen sensors.
| Consideration | Implication | Risk Level |
|---|
| Engine Damage | Washed cylinder walls, premature wear, potential misfires. | High |
| Exhaust System Damage | Melts catalytic converters, destroys oxygen sensors, damages mufflers. | High |
| Legal Consequences | Violates federal and state emissions laws (EPA, CARB); can result in heavy fines. | High |
| Fire Hazard | Potential to ignite flammable materials under or near the vehicle. | Severe |
| Safety | Can cause panic, accidents, or injuries to bystanders. | Severe |
In short, while it looks dramatic in movies and at drag strips, making a car shoot flames is a costly and risky modification. The potential for damaging your vehicle and facing legal penalties far outweighs the visual effect. If you're determined, consult a professional performance shop that specializes in track-only vehicles.
