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Drag Racing: Pushing the Absolute Limit of Cars

Written by Kevin Jennings

Drag racing first began in California in the 1930s, though its popularity wouldn’t really take off until the 1940s following World War II. Veterans featured prominently in the sport, and many races took place at decommissioned aircraft bases, as the long, straight, and isolated landing strips were perfect for racing their cars.

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              As the sport grew in popularity throughout the 1940s, it largely remained an underground pastime. Then in 1951, the National Hot Rod Association (NHRA) was founded as the governing body for official drag races. There are both the official, regulated races that take place as well as illegal street racing. For today’s episode, we’ll be focusing only on the official motorsport as there are a lot of differences between the two.

History

              When the NHRA was first founded back in 1951, drag racing was a lot different than what we see today. Most notably, there would be twice as many vehicles in each race. There were still the same number of dragsters, but cars used a push start technique. This is exactly what it sounds like: the dragsters would simultaneously be pushed forward by another car to get up to speed and then fire off their engines.

              There were a number of logistical problems with this. It slowed down the event considerably, as everything needed to be lined up perfectly to commence. This would be boring for spectators, and could cause the dragsters to overheat if there was too much time between the burnout and the actual race. In 1976, the NHRA mandated that all cars must be self-starters.

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              So what are those burnouts we mentioned? Burnouts are when the car spins its wheels quickly in place, often creating lots of smoke. The purpose of this is twofold. First, the heat softens the rubber so that it will have more traction at the start of the race. It also leaves a layer of rubber on the track to further increase traction. The second reason is to remove any non-rubber debris that the tire may have picked up. Originally cars were pulled back to the starting position after their burnout, but in 1980 it was mandated that all cars have a reversing system to put themselves back into place.

              Since the beginning of drag racing, the primary fuel has been nitromethane, often referred to as “nitro fuel” or simply “nitro”. This is very different than nitrous which you may be familiar you with from street racing and video games, as nitrous is a gas injected into the engine rather than the actual fuel itself.

              There was a brief period from 1957-1963 where nitro fuel was banned by the NHRA on the basis that it was unsafe. This is simultaneously both true and untrue. Like gasoline, nitromethane is combustible, but it is far less energetic than gasoline. It is also less dense, so the same volume of gasoline is several times more dangerous than nitromethane as an explosive or incendiary agent. However, nitromethane fumes are far more dangerous. It is not uncommon at a drag race to see people wearing gas masks, and those that aren’t are likely to have red and watering eyes. Nitro fuel is also extremely toxic if ingested, but that doesn’t come up any more often than drinking gasoline does so it’s a bit of a moot point.

              But if nitro fuel is less powerful than gasoline, why is it the fuel of choice for the fastest cars around? The answer is its chemical composition of CH₃NO₂, or more specifically the O₂ portion. Nitromethane has its own oxygen inside it, which means the engine needs to take in far less air and can instead be filled with more fuel. It takes almost 9 times as much air to burn a gallon of gasoline as it does to burn a gallon of nitro. Even though it’s less efficient per pound, because so much more nitro can be burned in the same amount of time, it results in a roughly 250% increase of power from the fuel choice alone.

              Of course, part of being less energetic is that the nitro doesn’t burn as quickly. In fact, the engine pumps faster that the fuel can burn off, meaning that when the exhaust valve opens it takes burning nitro with it, resulting in the flames you see shooting out of a dragster’s exhaust pipes.

              As for the courses themselves, for a long time the standard race would be a quarter of a mile, or 1,320 feet. However, this has been decreased to 1,000 feet for the fastest classes of cars, and many others are beginning to adopt it at well. It was an unpopular change at first, but extremely necessarily. Cars continue to get faster, and many locations simply don’t have enough space for the fastest dragsters to slow down after a quarter mile race without them sailing off the end of the road. This rule was changed following the fatal crash of driver Scott Kalitta in 2008.

Competitions

            There are quite a lot of variations on the structure of competitive drag racing, but the most popular system is a traditional tournament bracket. Cars are seeded based on their qualifying times, then the first round of the bracket is constructed so that the first place qualifier competes against the last place qualifier, second versus second to last, and so on. It is then a single elimination tournament. With each race lasting only a few seconds, you can be sure that the setup for every race is extremely precise.

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              Before each race, the cars are run through a “water box” and then perform their burnouts. After this, it is time to line up at the starting line. Originally, as is done in street racing, races were started by someone standing between the two lanes and dropping their arms to signal the drivers to go. This has since been replaced with an elaborate electronic system of lights known as a Christmas tree. Current NHRA trees contain six lights: red, green, three amber, and a blue light split into two halves.

              There are two sensor beams per lane at the starting line of the race. When a car crosses the first sensor, it is considered “pre-staged” and the first half of the blue light goes on. Once the car reaches the second sensor it is staged, turning on the full blue light. From the moment one car is fully staged, the other car has a limited amount of time, normally 10 seconds, to get into the staged position or they are disqualified.

              After both cars have been staged, the light is then put on a random timer. The random element is important so that the drivers have to pay attention rather than just anticipating how long until they can begin. There are various patterns in which the amber lights can flash depending on the category of the race. For example, once the cars are staged in the professional class, after a random delay all three amber lights will illuminate at once followed by a 0.4 second delay and then the green light. Different classes use different patterns, but it is always some combination of the amber lights followed by the green light.

              Once the light turns green, it is off to the races! Although in the top fuel category that only lasts about 4 seconds. There are various additional rules such as handicaps and breakouts that can be put into play, but in general the winner is whoever crosses the finish line first. As long as there isn’t a red light.

              In the race, there are two different things being measured. One is the car’s speed and the other is the driver’s reaction time. If a driver leaves the starting line, as indicated by the sensors, before the light has turned green, their light will turn red and they are disqualified. However, if both drivers leave before the green light, only the one who left first will get a red light. This means you can win despite screwing up, so long as you don’t screw up as bad as your opponent.

              The system also means that the car that took longer to complete the race can still win, even without a red light. Remember, it is both the car’s elapsed time and the reaction time that are being measured. This isn’t dissimilar to any other race, but when the variation in speeds among the top cars is only a fraction of a second, the driver’s reaction time suddenly becomes a lot more important. If your opponent’s car was 0.1 seconds faster than yours but you were able to leaving the starting line 0.15 seconds faster than your opponent, then the slower car will win the race.

              After the winner of the race is declared in an NHRA competition, the driver and their team will then have 75 minutes to rebuild the engine and do any repairs to the chassis that are necessary, though some organizations allow for longer. This is not some sort of “just in case” safety precaution, either. Top fuel cars can reach speeds of up to 335 mph (540 km/h) and go from 0-100 mph (160 km/h) in as little as 0.8 seconds.

If you’re wondering how we can produce an engine that can sustain that level of performance, the simple answer is we can’t. With proper maintenance a Honda Civic’s much more modestly performing engine can last for about 5,000 hours. These engines, however, have a life expectancy of about four seconds.

Top Fuel

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            There are at least 25 different classes of drag racing, but the fastest among them all are the top fuel dragsters and top fuel funny cars. Ironically, the so-called “funny cars” look much more like you would expect from a car. Under current rules, a typical top fuel dragster is 25 feet long and weighs 2,320 pounds. Both sets of top fuel cars get their name because they burn a solution of methanol with up to 90% nitro fuel.

              The raw power of these cars is absolutely staggering, largely because they make so many sacrifices. There is no transmission. There is no cooling system, relying on the liquid nitromethane to cool the engine before it’s ignited. After each race, the pistons will almost certainly have broken and the intense heat generated by the engine will have welded certain parts of the engine together.

              The engines are based on a Chrysler RB Hemi, but it uses entirely specialized parts. The engine block, pistons, cylinder heads, and connecting rods are all made out of aluminum. After each race, the engine is taken apart and repaired, with pistons and other pieces needing to be replaced after every run.

              Because of the ephemeral nature of these engines, it’s difficult to run tests to gauge things such as horsepower. Based on the cars weight and performance, they have been calculated as outputting between 8,500 and 10,000 horsepower, twice as much horsepower as a diesel locomotive. Test performed in 2015 shows engines capable of outputting 11,000 horsepower, but this is unlikely to be sustained for an entire race.

              For as long as the sport has existed, top fuel dragsters were the fastest drag racing cars around, and some of the fastest cars in the world. The current record for shortest elapsed time in a 1,000 foot race is held by Brittany Force with a time of just 3.623 seconds, set in 2019. Brittany also has the record for the top speed of 338.17 mph also set in 2019, though at a different race. Not only does she have the shortest elapsed time and highest top speed, she has nine out of the ten highest top speeds, records she began setting only three years after beginning her profession racing career in 2013.

              However, despite the dominance of top fuel dragsters since the creation of the sport over 70 years ago, the tables have finally turned. In 2017, a new top speed record was set in the top fuel funny car division. Driver Robert Hight hit a speed of 339.87 mph in 2017 breaking the previous record by more than a full mile per hour. Though he would not quite hit that speed again, later that same year he would once again break 339 mph, as would another funny car driver in 2019. In addition to those two, two other funny car drivers have exceeded Brittany’s dragster record showing that the era of dragster’s dominance may have finally come to an end.

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Wrap Up

              The speeds that dragsters can achieve are not only incredible, but they keep on improving. The 250 mph barrier was first broken in 1975, then 17 years later the world would see the first 300 mph time. Engines kept improving and it was only another 5 years before 320 mph was reached and another 2 years after that, in 1999, the first 330 was recorded. There was so much improvement so quickly, however it’s been over 20 years since a milestone speed has been achieved.

              Some people feel that this is because of strict requirements on the construction of the engines, much of which is using decades old technology that is considered to be outdated. It’s also possible that we’re simply reaching the absolute limit of what is capable using nitromethane fuel in a car.

              Either way, even though the rate of improvement has dramatically decreased, improvement is still happening. With a 339.87 achieved over five years ago and two other times above 339, it is clear that 340 is not only possible, but could happen at any moment. As for further milestones like 350 mph, it may be that such speeds will be impossible without a complete reexamination of the engine design. But with a 340 seemingly imminent and races lasting less than four seconds, be sure not to blink or you’ll miss it.

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