Ameer Randolph
The sight of a car spitting flames is undeniably cool, but why does it happen? There are several ways to make a car spit flames, but the most common cause is when unburnt fuel from the engine enters the hot exhaust passageway, causing it to ignite and produce flames. This can happen when a rev limiter cuts the ignition but leaves the fuel on, or when too much fuel is added at high RPM, causing a backfire when you lift off the throttle. While it may look awesome, it's important to note that it's not good for your engine and can even be dangerous. So, while you might be tempted to try and make your car spit flames, it's probably best to leave it to the professionals!
| Characteristics | Values |
|---|---|
| Reason | Unburnt fuel dumped into the exhaust system catches alight |
| Cause | Rev limiter that cuts ignition but leaves fuel on; too much fuel added at high RPM |
| How to induce | Quickly close throttle at high-load, high-RPM; accelerate hard with wide-open throttle then snap it shut |
| Engine impact | Bad for the engine, bodywork, manifold, and turbo |
| Hearing impact | Can cause permanent hearing loss to pedestrians or people in cars |
Explore related products
Ignition tuning
One common ignition tuning technique that can lead to flame-spitting involves the use of a rev limiter. This device cuts the ignition while keeping the fuel supply active, resulting in a backfire when the throttle is released. This backfire, combined with the rapid closure of the throttle at high RPM and high load, creates the perfect conditions for flames to burst from the exhaust pipes.
Another factor in ignition tuning that can cause flame-spitting is the setting of the lowest MAP bins in RPM-MAP-based ECUs. These bins are often set at the maximum vacuum achievable while quickly opening the throttle. However, when the throttle is abruptly closed at high RPM and high load, the MAP can dip below this value, resulting in a rich condition that produces popping and flames. While it is possible to tune out this issue by adjusting the MAP bins, it is generally avoided in race car applications as it compromises the resolution of the fuel tables during normal operation.
Additionally, some race cars are intentionally tuned to spit flames for aesthetic purposes. This is achieved by keeping the fuel supply active during a closed throttle, resulting in unburned fuel being ignited in the exhaust system. While this may be visually impressive, it is important to note that running an engine excessively rich can have negative consequences for the vehicle and the environment.
In summary, ignition tuning plays a crucial role in the phenomenon of flame-spitting in top-fuel funny cars. Through specific techniques, such as rev limiter adjustments and MAP bin settings, race cars can be tuned to produce impressive fireballs. However, it is important to be mindful of the potential risks and environmental impact associated with excessive fuel enrichment.
Flex Fuel: Friend or Foe to Your Car?
You may want to see also
Explore related products
Rev limiter
The phenomenon of race cars spitting fire is due to fuel and/or ignition tuning. One of the common ways to achieve this is by using a rev limiter.
A rev limiter is a device that prevents an internal combustion engine from exceeding its maximum safe speed, the redline. The rev limiter works by interrupting the spark in the spark plugs, which stops the fuel from burning and prevents the engine from creating power. This can be achieved by cutting the ignition but leaving the fuel on, which causes unburnt fuel to be dumped into the hot exhaust system and catch alight, resulting in flames.
To create a rev limiter that spits flames, one must stop the ignition signal at a specific frequency or RPM. This can be done by connecting the shaft position sensor to an oscilloscope to get a clear signal and increase the frequency as the engine speed increases. Then, the frequency is converted to a voltage, and a potentiometer is used to create a voltage divider to set the threshold easily.
Another way to make a car spit flames is by using an anti-lag or two-step system. An anti-lag system works by combusting fuel after the engine and before the turbo, reducing turbo lag and ensuring extra unburnt fuel enters the exhaust. A two-step system, on the other hand, provides two rev limiters: a lower limit for better tyre hookup and a higher, natural red line limit. While holding at the lower limit, fuel continues to be pumped into the combustion chamber but is not always ignited, making its way into the exhaust and potentially igniting.
While spitting flames may look cool, it is important to note that it is not good for the engine, bodywork, or safety. It can also be illegal in some places. Additionally, it can cause hearing loss in people nearby due to the loud pops and bangs.
Cars: Fuel Consumption While Stationary, Explained
You may want to see also
Explore related products
High-RPM, low load cells
There are several reasons why race cars, including top fuel funny cars, spit flames. One of the most common ways this occurs is due to the engine tuning and the use of rev limiters. A rev limiter can cut the ignition but leave the fuel pump running, causing unburnt fuel to be dumped into the exhaust system, where it ignites and produces flames. This can also occur when too much fuel is added at high RPM, in what are known as low load cells in the fuel table. This results in a backfire when the throttle is lifted.
Another way to induce flames from the exhaust is by using an antilag system, which combusts fuel after the engine and before the turbo, keeping the turbo spinning when there is a low flow of exhaust gases. This system also ensures that extra unburnt fuel makes its way into the exhaust, producing flames. Additionally, some cars naturally run richer fuel mixes, resulting in more combustible gases in the exhaust system, which can lead to flame spitting.
Modern race cars have become less likely to spit flames due to improvements in engine efficiency and the use of particulate filters, which trap unburnt fuel particles. However, some drivers still enjoy the spectacle of flames and may modify their cars to produce them, despite the potential risks to the engine, bodywork, and the possibility of setting the car on fire.
Fuel Filter Hesitation: Can It Cause Car Starting Issues?
You may want to see also
Explore related products
Anti-lag systems
The spitting of flames by some top fuel funny cars is associated with anti-lag systems (ALS). These systems are designed to reduce turbo lag, or effective compression, in turbocharged engines. Turbo lag refers to the delay between opening the throttle and the turbocharger delivering meaningful torque. Anti-lag systems were first used in turbocharged cars in Formula One racing in the 1980s and later became common in rally cars due to increased turbo lag from mandated restrictors.
There are several types of anti-lag systems, most of which involve making fuel and air available in the exhaust manifold. The burning and expansion of this mixture keep the turbocharger spooling during periods when the throttle is temporarily closed, such as when shifting gears or braking to enter a curve. Some systems use a bypass valve to feed air directly to the exhaust manifold, where it mixes with partially combusted gases from the engine, igniting them again and spooling up the turbo. Other systems use motor generators to keep the turbine spinning when off-throttle, converting heat energy into battery-stored electric power.
While anti-lag systems provide performance benefits, they also have several drawbacks. They can significantly increase fuel consumption and shorten the lifespan of the turbocharger due to the violent pressures and high temperatures created. Additionally, they can produce loud pops and bangs, causing potential hearing damage to nearby individuals. They may also not be suitable for road cars due to their impact on catalyst converters and emissions.
Uncovering Car Fuel Gauge Deception: Tricks and Fixes
You may want to see also
Explore related products
Rich fuel mix
The phenomenon of race cars spitting flames is often attributed to a rich fuel mix, among other factors. This occurs when there is an excessive amount of fuel in the combustion chamber, which is not fully burned during the combustion process. As a result, the unburned fuel is expelled into the exhaust system, where it can ignite and produce flames.
To create a rich fuel mix, one common method is to rapidly accelerate to high revolutions per minute (RPM) and then abruptly release the throttle. This action causes a significant amount of fuel and air to be dumped into the combustion chamber. However, when the throttle is quickly closed, the fuel and air mixture is no longer needed for propulsion and is instead directed into the exhaust system. This excess fuel, when combined with the hot exhaust pipes, can ignite and produce impressive fireballs.
The use of a rev limiter that cuts the ignition but keeps the fuel supply active can also contribute to a rich fuel mix. Additionally, certain engine configurations, such as rotary-powered engines, naturally run richer due to the higher volume of combustible gases passing through the exhaust system. This inherent characteristic makes them more prone to spitting flames.
It is worth noting that while the sight of flames shooting from a car's exhaust may be captivating, it is not without consequences. Running a rich fuel mix can have negative implications for the engine, the bodywork, and the environment. It can increase the risk of setting the car on fire and may also lead to issues with the manifold and turbo if not carefully managed.
Furthermore, modern advancements in engine efficiency and the introduction of particulate filters have made it less common for cars to spit flames. These filters are designed to trap unburned fuel particles, reducing the likelihood of them igniting and exploding in the exhaust system. Nonetheless, some car enthusiasts still seek ways to induce this fiery display, often by modifying their vehicles or adjusting the engine management system.
Old Fuel's Impact: Why Your Car May Be Smoking
You may want to see also
Frequently asked questions
There are a few reasons why this might happen. One is a rev limiter that cuts the ignition but leaves the fuel on. Another is if too much fuel is added at high RPM, low load cells in the fuel table, which results in a backfire when you lift off the throttle.
One way to do this is to accelerate hard with a wide-open throttle, then quickly snap the throttle shut. This causes unburnt fuel to be dumped into the exhaust system, where it will ignite.
Yes, it can be bad for your engine and bodywork, and you might set your car on fire. It can also cause permanent hearing loss to pedestrians or people in cars next to you, depending on how loud it is.
Yes, some cars spit flames stock. For example, Lamborghinis have been known to catch on fire when neutral revving and popping.
