How top-fuel drag racing cars reach 11,000 horsepower

How top-fuel drag racing cars reach 11,000 horsepower

Like any self-respecting petrolhead, I’m fascinated by all things internal combustion. I’ve been to race tracks all over the world to see the best riders and drivers on two and four wheels respectively. Few experiences are so engrained in my mind as hearing two 11,000-horsepower Top Fuel trotters blast off the starting line. After such a deep-seated experience—which could have fooled me into thinking the world was ending—I did some digging to find out what drives these machines.

Drag racing is one of the simplest forms of motorsport; without corners, pit stops or gear changes it comes down to “whoever is fastest wins.” The sport started with a simple “run what you’ve brought” ethos, growing large amounts of fun for little cost. However, the top tier of the sport has since evolved into a horsepower shooting spree, with the fastest Top Fuel dragsters cranking up to 11,000 horsepower.

For an internal combustion engine to function, you need three ingredients: fuel, air and spark. These are the building blocks of horsepower. The engine in a Top Fuel dragster is largely similar to what you have under your daily driver’s hood. The (frankly ridiculous) amount of power that comes out of these machines is made possible by optimizing that mixture of fuel, air, and spark.

Starting with fuel, these race cars use nitromethane instead of gasoline. This alternative “top fuel” (hence the name) is essentially gasoline premixed with nitrous oxide. However, nitromethane is much less volatile than gasoline. Ergo, you can burn a lot more nitro in the combustion chamber, leading to a lot more power from each explosion in the engine. Top Fuel dragsters are unsurprisingly thirsty machines, burning between 16 and 23 gallons of fuel during the warm-up, burnout, staging and four-second run.

This staggering fuel consumption not only provides a lot of power, but also cools the engine. These dragster engines do not have cooling radiators. So how do they not overheat right away? Another unique advantage of nitromethane is that it has an incredibly high latent heat of vaporization, meaning it can absorb a tremendous amount of engine heat as it evaporates. The enormous amount of fuel injected into the combustion chamber ensures adequate cooling.

During each run, the incredible amount of heat emitted from the combustion chamber melts the spark plugs.

Top Fuel engines are actually quite simple in design. All engines competing in National Hot Road Association of America (NHRA) approved events follow the same design as Chrysler’s original 1964 Hemi Elephant 500 cubic inch (8.1 liter) racing engine. The name “Hemi” came of the engine semicircular (spherical) combustion chambers with two valves. This design allowed for larger valves, allowing much more air to enter the combustion chamber. And what gives you more air? More power.

While spinning a huge engine with equally sized valves sounds like the perfect recipe for big power, it’s not enough when it comes to drag racing. This is where a supercharger (also called a blower) forces even more air into the combustion chamber to produce more power. However, superchargers take power to make power; the blowers on Top Fuel dragsters generally require more than 700 horsepower to supply the car with the right amount of air to produce the magical 11,000 horsepower. This is commonly referred to as parasitic loss.

Then we come to the spark. Without enough spark, Top Fuel engines run the risk of hydrolock – where there is more fuel in the combustion chamber than can be ignited – which can blow the engine’s cylinder head clean. This is the main reason why these engines use two spark plugs per cylinder, powered by dual magnetos that produce up to 44 amps of juice. However, during every ride, the incredible amount of heat emitted from the combustion chamber melts the spark plugs.

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The spark plugs are not the only components that get roasted in the engine. During a race, Top Fuel machines go through otherworldly stress levels – so much so that the pistons, rings, connecting rods and spark plugs only survive four seconds. To provide some perspective, most engines under the hood of road vehicles have a service interval of 3,000 hours.

Drag racing is often mistakenly labeled as “boring” motorsport, but it’s actually quite the opposite when you understand what’s going on mechanically. Any vehicle that can catapult itself to over 300 miles per hour in just over three seconds is a modern marvel.

Matt Crisara
Matt Crisara is a native Texan with an unbridled passion for cars and motorsports, both abroad and domestically, and as Autos Editor for Popular Mechanics, he writes the bulk of automotive digital and print coverage.

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