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NHRA 101: How To Run A 10,000hp Nitro Car

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NHRA 101: How To Run A 10,000hp Nitro Car


Nitromethane, it’s a word that strikes up ideas of calamity or rapidity. The funny part is that both can be observed at a NHRA national event in the Top Fuel and Funny Car classes as they shake the ground and pass the 1000-foot mark in less than 4 seconds, or explode into bits when it all goes wrong.

The idea of getting down a drag strip seems so simple as it’s not that far; you can see it and it’s a straight line. However, the process of getting a nitro car down the track is far more complicated than what you see from the stands…

The first thing is not even a part of the car. Track prep is vital to making sure all cars can go down the strip without ‘blowing their tires off’ or that smoke show you see those Top Fuel and Funny Car guys do when it does go wrong. While it looks more violent for them, all cars can encounter tire shake and cause traction loss. A chemical is sprayed down the track to help enhance the traction of the concrete and asphalt the racing surface is made of. This also must be done every time a car ‘oils down’ when an engine or drivetrain lets go.

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Prior to every run, crew members check the track’s condition from the heat, humidity, and atmospheric condition.

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The traction available is also determined by a very specific and special tool known as a track meter. A member of the crew will stand on this cross-looking device and attach a torque wrench to the top of it. What that is attached to is a piece of rubber that’s like the drag tires they use. By turning the torque wrench to certain degrees, the crew chief can get a better understanding of how much traction is available and how quickly they can apply the slider-style clutch along the track before traction is lost. It’s a very interesting tool but one needed by teams to ensure they run consistent times and run the car to its maximum available grip.

The Start & The Smoke

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Before performing the crowd-pleasing burnout, you must start a nitro car, and that’s not as easy a task as it might seem. You can’t just light up the mix like you can a gasoline or even an alcohol car. The fuel is a methanol composition with up to 90 percent nitromethane as mandated by the NHRA. The nitromethane, interestingly, is created by either treating propane with nitric acid at 350°C to 450°C (662°F to 842°F) or can be created with a reaction of sodium chloroacetate (which can also be used to make PVC plastics) and sodium nitrite (most commonly used as a food additive against microbial growth) mixed into a water solution. It’s not the same as nitroglycerin, though, as that’s more of an organic nitrate than a man-made nitro compound like nitromethane is. Nitromethane can also be used in anything that needs a monopropellant, like rockets, since it contains its own oxidizer like nitrous oxide. You can also use nitromethane to create hydrazine, an unstable monopropellant that is forbidden for use in the US.

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Nitromethane is very, very powerful when it burns. In fact, it’s 2.3-times more powerful than gasoline for the same amount of oxygen used. Also, because nitromethane contains its own oxidizer, less oxygen needs to be introduced to burn the nitromethane/methanol mix. The problem with it as a fuel, though, is that it burns very slowly, which is an issue when you’re trying to start a nitro car. The first thing you see before and during that start up is a crew member squeezing a bottle into the blower hat, the part where you see the butterfly valves that open on the top of the engine. Once fired and the engine is running on the gasoline, the member will then turn the valve from the fuel pump to start feeding the nitromethane mixture. You can even hear when it does because the pitch will change and become deeper. That slow burn is also why you’ll see some sprays of white liquid coming out of the header pipes before the burnout is done. That’s unburned fuel being sprayed out.

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Once these guys and gals are strapped in, they can only see out the front and sides. There are no mirrors so another crew member aides the drivers back to the starting line, making sure the car is in the groove that the crew chief feels is the right one for that run. Again, this determined by all the data he or she has acquired throughout the weekend and even events prior. You don’t really get a chance to put the car back right, especially with the longer Top Fuel cars. You’ll also find crew-members wiping down the tires in an effort to rid them of any rubber, dirt, debris, and even any leftover water that may have gotten on them as the car reversed back. Nitro cars need all the grip afforded to them and any loss of traction that wasn’t planned can be devastating.

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Before pre-staging, the crews do one final look-over and pull a pin on the blower hat. That is a limiter that doesn’t allow for full fuel during the burnout. Up to this point, only enough fuel has been allowed to flow into the engine to keep the blower cool and run the engine while the tires are heated.

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Running at full fuel increases the chance that a failure will occur, and when failure happens in a nitro car, it’s enormous to say the least. At this point, crews will also begin to turn on any data-logging and change the mapping of the slider clutch from burnout to the one for the pass.

Staged For The Battle

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Now, we’re finally getting to the point you can pre-stage the cars. This is just before the stage beam and is used to show the driver is nearly prepared to make their run. The driver is aided by a crew member to find the pre-stage beam. That indication between driver and member is unique to each, so there is no right or wrong way except if the car staged too early. Though, you can play mind and mechanical games here. Stay in pre-stage for a while and you can start messing with your competitor’s head. You usually don’t want to be the first guy staged, but you can also ruin a driver’s groove by staging quickly.

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You also normally only want to just cross the stage beam. It may only be fractions of an inch, but you are given that much more space to react to the .400-second pro tree light scheme. However, the theoretical advantage of the deep stage – where you cross so far that you turn off the pre-stage light but the stage light is still on – is that you’re that much closer to the finish line. That comes at the cost that you need to be dead on with your reaction time or risk a disqualifying red light and ending your run before you even get to the 60-foot mark.

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Once a driver (in a bye-run) or both drivers stage up, the starting official presses the button to begin the timing equipment of the run. Once that button is pressed, the three yellow lights of the tree all light up nearly at once and then the green light turns on. The time between the top yellow light to the green light is only .400-second. That used to be how the NHRA described a perfect light, however, now it’s the measurement of the reaction by the driver to just before the green light turns on to the time the front tires break away from the stage beam. A perfect light is .000, however most reaction times range from .022- to .115-second in the pro classes. An average person’s eye blinks in .033-second, just to give some indication on how fast they are reacting to that light.

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Once that throttle goes all the way down, 10,000 horsepower is unleashed at its full fury. The driver experiences a full 8Gs on their bodies at launch and it flattens out to 4Gs in the middle of the run. During that time, the driver is fighting the car to keep it going straight. Each time a cylinder lights off, it pushes the car in the opposite direction. Yes, the exhaust is coming out with such force that it not only aids in acceleration but keeps the chassis planted to the ground. When a cylinder fails to fire, the car will begin to move towards that side as more force is being applied to the opposite. Oh, that yellow-white color coming out of those headers is also burned hydrogen. When nitromethane burns in the absence of oxygen, which happens in the combustion chamber of that 8.19-liter (500ci) engine, it produces hydrogen which is then ignited upon its exit.

Even When It All Goes Right, It Can All Go Wrong

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Catastrophe is ready to strike every time the nitromethane mix ignites in the cylinder. Spark plugs can melt down and make a cylinder no longer fire. If that happens, the engine can hydraulic. So, instead of hydrolock and engine shutdown, the compression of the nitromethane that doesn’t get burned can force the head of the cylinder to lift off with enough force that it’s an explosion, one so hard that it can knock a driver unconscious, lift the car into the air, and even cause the rear tires to explode (if the shrapnel didn’t get it first). If the mixture backfires into the supercharger, it can blow it off the block.

However, if none of these happen and the run goes perfect, a Funny Car can cross the finish beam in 3.8-seconds at 330mph (531km/h). A Top Fuel car, on the other hand, can turn in an average ET of 3.7 seconds at 335mph (539km/h).

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Now, you must slow it down and turn off the track. Brakes alone won’t be enough when you’re still traveling at 4Gs and 300mph (482km/h); it can be done, but you’ll probably end up in the sand trap at the end of the track, too. That’s where the parachutes are deployed and that’s no easy ride either. When fully deployed, a parachute can pull 7Gs in the opposite direction and slow the car to more reasonable speed for the friction brakes to slow the cars further and be more manageable for the turn in.

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Parachutes can also aid when things start to go wrong during a run, as deploying them during a sashaying moment (aka a ‘tank slapper’) can help slow and straighten the car out. Yes, doing so ends the run, but you don’t destroy the car. Maybe.

By the way, all those g-forces are more than astronauts experience on even the harshest of launches as they only see about 4Gs to 5Gs on average.

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Teardown & Rebuild In 40 Minutes, Or Else

While the driver is done and the car is towed back to the pits, the crew still has work to do. After each round the engine must be torn down, inspected, and rebuilt before it can hit the strip again. The forces exerted on these cars are tremendous and the wear and abuse is even more impressive.

Oh, when we say ‘torn down’ we mean the block is stripped of everything; blower, pistons, crankshaft, fuel system – it’s all got to come off be inspected, repaired and/or replaced. The clutches are surfaced, parachutes are repacked, and everything is put back together and warmed up before making another run. This is also done in 40 minutes and is a time mandated by the NHRA, too. You can’t take longer or your competitor will be given a bye-run and a free win. Well, not a free win.

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Each time a Top Fuel or Funny Car goes down that 1000-foot track, it costs, on average, $4000. Well, that’s if everything goes right. Where does the money go? Well, nitromethane costs about $35 to $40 per US gallon and a nitro car goes through it at about 65 US gallons per minute. Each spark plug is used up in the engine and each one costs anywhere from $5 to $9 each and there are two per cylinder per run. Copper head gaskets are replaced after every run, and those are about $200 per side per run. Tires usually last about four to six runs and cost $900 each. So, you can see the costs begin to add up. It makes you wonder how any self-funded team can do it, though there are a few.

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It was a private team, Dote Racing, that allowed Leah Pritchett to get her start and now she’s the fastest woman in the NHRA and the fastest driver (unofficially) in Top Fuel’s 1000-foot history having recently run a 3.654 elapsed time at 331.85mph (534km/h) in testing. John Force was once a privateer Funny Car driver before he became the household name for the NHRA and the 16-time Funny Car champion.

A career in nitro cars doesn’t always work out, but when it does there is nothing quite like it. Fitting as it’s exactly like a run in a nitro car – flirting between that fine line of glory or disaster. There is nothing like them and it’s why crowds gather into the stands when these cars fire up.

Written by Justin Banner
Instagram: jb27tt
Facebook: racerbanner

Photos by Larry Chen
Instagram: larry_chen_foto
larry@speedhunters.com

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