How a Top Fuel Dragster Works

The people who built the predecessors to Top Fuel cars—engineers, mechanics and amateur drag racers around the world—eventually came to the conclusion that a nitromethane blend is the best type of fuel for these particular types of engines. Nitromethane is also known by its chemical makeup, CH3NO2. It's a dangerous and volatile substance that's often used for pesticides, medicine manufacturing, heavy duty cleaning solvents and even rocket fuel. Nitromethane burns at a relatively slow rate compared to other fuels, and some unburned nitromethane may escape through the exhaust system and ignite when it comes into contact with the atmosphere, resulting in the exhaust pipe flames that contribute to the spectacle of a Top Fuel race.

An engine that runs on nitromethane is typically much lower compression than a gasoline engine [source: Davis]. Unlike gasoline, nitromethane carries oxygen, so the engine doesn't need to force in as much air for the combustion cycle, allowing it to run at lower compression. Still, all of the connections need to be inspected and repaired on a regular basis. For example, the welds on the custom headers start to fail after about 50 or so runs [source: Mazlumian]. If a Top Fuel car's engine is not running properly and unburned fuel builds up in the engine, it can explode with a force strong enough to crack the engine's head or block. 

Currently, Top Fuel run on a blend that's 90 percent nitromethane and 10 percent methanol, according to NHRA rules [source: Davis]. The methanol helps suppress detonation, which makes the fuel more stable. The fuel is tricky to blend at the proper ratio because it's mixed by weight, which depends on its temperature. And to further complicate matters, the fuels themselves can vary in purity by a few percentage points. Blending top fuel for stability and premium power can yield varied results; in most cases, the fuel works as intended. Nitromethane can be blended with substances other than methanol to help boost its power potential, but such tactics are banned by the NHRA and most other racing organizations, in part because other fuel blends are more dangerous and also harder to regulate.

Even though whoever gets to the finish line first is crowned the victor of an NHRA drag race, that doesn't mean the winning car is necessarily the fastest. If a car is the first off the line, that's a huge advantage in a race that only covers a short distance. Even if another car has a faster top speed, it might not be able to make up the lost ground to take the win. 

Top Fuel cars take off from the starting line and reach a speed of 100 miles per hour (160.9 kilometers per hour) in less than a second. This makes them the fastest accelerating cars in the world. A Top Fuel engine's power reaches the wheels in a fraction of a second. Top Fuel drivers endure G-forces similar to astronauts during a space shuttle launch. And almost just as quickly, they need to stop. Since these cars would wear through brakes pretty quickly at more than 300 miles per hour (482.8 kilometers per hour), Top Fuel dragsters are equipped with a special type of primary braking system. After crossing the finish line, the driver hits a switch that deploys two parachutes behind the car, and the intense wind resistance slows the car, minimizing the risk of mechanical failure.

Funny Cars, another class of drag racing vehicle, use the same kind of engines as Top Fuel cars, but there are plenty of differences. In Top Fuel cars, the engine is situated behind the driver, but Funny Cars put the engine up front. The different wheelbase of Funny Cars may account for some of the differences in speed and acceleration since the huge amount of power going to the rear wheels can cause a lot of extra movement as the cars zip down the strip. 

Funny Cars use the wheelbase of a production car from the model year 2000 or later, and then a fiberglass replica of the body is constructed to reduce weight. The rules for using production cars offer a lot of leeway. Racers can use sports cars, coupes, or sedans from any domestic or import auto manufacturer, as long as the car was originally mass produced. In other words, race teams can't modify concept cars, show cars or hand-built boutique cars. To be eligible under the NHRA's rules, the car must have been built on a factory assembly line. 

Top Fuel drag cars and Funny Cars have similar performance specs, thanks to the related mechanical components. Over the 1,000-foot (304.8-meter) straightaway, both types of dragsters reach speeds above 300 miles per hour (482.8 kilometers per hour) and complete the distance in three to four seconds, burning about 1.2 gallons (4.54 liters) of nitromethane blend per second, and about 17 gallons (64.35 liters) per race [source: Mazlumian]. Another way to get a sense of these cars' capabilities is to look at the records. As of 2022, the record for fastest Top Fuel car in the series was 338.94 miles per hour (545.47 kilometers per hour), held by Brittany Force, and for the Funny Car, the top-speed recorded is Robert Hight's 339.87 miles per hour (546.97 kilometers per hour). Brittany Force completed a Top Fuel run in just 3.641 seconds, and Robert Hight's Funny Car record is 3.793 seconds.

Motorsports fans are advised to wear some kind of ear protection when they're watching Top Fuel racing live. Easily obtainable foam earplugs, like the kind that you'd wear to catch some sleep on a long plane trip, can cut the sound by about 20 decibels [source: McGee]. That's not a lot, as you'll see, but it's better than nothing. Hearing damage is usually permanent. And Top Fuel dragsters are the worst noise offenders out there.

Top Fuel dragsters are the NHRA's loudest cars, in part because of the way the engine is mounted. If it was under a hood like a normal car, there'd be at least some insulation to muffle the sound; however, it's completely exposed, and all the engine's workings are right out there—oh, and there are no mufflers either. The NHRA once allowed a team of seismologists to stand at the starting line to measure the race the way they would measure an earthquake—the two cars rated a 2.3 on the Richter scale [source: McGee]. That's equivalent to a minor quake. 

According to ESPN, even though the NHRA will let seismologists take meter readings, they've never recorded official decibel levels, and it's unlikely they ever will. It's all part of the mystique surrounding the sport. In 2010, an ESPN reporter scrambled around to find a sound meter capable of testing a Top Fuel drag run— the highest he could record was 140 decibels, with the meter blinking to indicate its capacity was topped out [source: McGee]. Experts estimate Top Fuel cars can reach over 150 decibels, a level that can cause physical damage to the eardrum. For comparison's sake, a typical rock-concert is about 104 to 120 decibels.

There's no sign of Top Fuel popularity slowing down anytime soon. In fact, over the years, the cars themselves have become even more powerful. And the faster a Top Fuel car goes, the louder it gets, which means that as technology continues to improve, more and more drivers are encountering hearing loss [source: McGee]. Fans will have to deal with more potential hearing damage, too. It's just one of the many well-publicized risks of racing, but for the drivers and the fans, the thrill of the race is well worth it.