As the green flag descends,43 cars emblazoned withmulticolored decals acceler-ate to race speed amid thedeafening roar of thousandsof fans. The smell of rubberpermeates the air as the dri-

vers immediately jockey for position. Only one driver willemerge victorious when the checkered flag lowers a

few hours and several hundred miles later.Welcome to NASCARthe uniquely Ameri-

can sport. NASCAR stands for the NationalAssociation for Stock Car Auto Racing, and itbegan in 1947. NASCAR has exploded in pop-ularity in recent years. It is a dangerous and

exhilarating sport. The cars are loud andfast. The drivers are as popular as movie

stars. And underneath the hood of everycar, chemical reactions are occurring

at a furious pace.The drivers and mechanics

who work daily with these carsthoroughly understand thescience behind them. And tomake things even more chal-

lenging, the rules change con-stantly, sometimes weekly.These constant rule changesforce race teams to modify theircars accordingly. And on top ofthat, each NASCAR track is dif-

ferent, creating the need for

adjustments to be made to the car, depending on the challenges ofeach particular track.

The skeleton of every NASCAR car is the frame. The frame is tubu-lar and is purchased prefabricated from the manufacturer. It is made ofsteel tubingsome round and some square. The thickness can vary,but the thickest part surrounds the driver and comprises the roll cage,which protects the driver in case of a collision. The front and rear tubingthe thinnest and designed to crush in case of a collision. This protectsthe driver, as the collapsible frame absorbs the bulk of the energy of acollision, as opposed to the driver. The frame is also designed to forcethe engine downward and onto the ground in case of a severe collision,and not into the driver.

Every NASCAR car has a few stock partshence the name stockcarbut these are strictly cosmetic. A stock part is a part that is madein an assembly line by the manufacturer. The only stock parts are thehood, roof, trunk lid, and front grill. The rest of the car is custom made.Each NASCAR car must use stock parts exclusively from one of the fol-lowing: Chevrolet Monte Carlo, Ford Fusion, Pontiac Grand Prix, orDodge Charger. Beyond that, the cars bear little resemblance to theirnamesakes.

A NASCAR car contains no glass, no doors, no back or passengerseats, no headlights, no brake lights, no speedometer, no gas gauge,no muffler, no stereo, no air conditioning, no glove compartment, nohorn, and no air bags! Instead of headlights, stickers are affixed to thefront of the car to resemble its parent stock car. The steering wheel isdetachable, making it easier to enter and exit the car. You do not needa key to start a NASCAR race caryou simply flip a switch and theengine roars to life.

Playing it safeSafety is paramount in the construction of every feature of a

NASCAR automobile. The windshield is made of Lexan, a very soft but

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ChemMatters, FEBRUARY 2007 5

extremelydurable material. It is so soft that it can

be easily dented or scratched, but it will notshatter. It is covered with layers of thin adhe-sive transparent film to prevent it from beingdamaged during a race. If a layer of filmbecomes scratched or dirty during the race, it can be quickly peeled off during a pit stop.Lexan is made from a thermoplastic polymerknown as polycarbonate. Thermoplasticssoften upon heating. Lexan is also used tomake iPods, CDs, and DVDs, and the sturdywater bottles used by hikers. It is so strongthat it is the chief component of bulletproofglass!

On the drivers side is nylon webbing inplace of a window, which is designed to keepthe drivers hands and arms inside the carduring a collision. It is equipped with a quick-release mechanism in case a quick exit fromthe car is required.

All driversmust wear a helmet,which is speciallydesigned for them,and is designed toprotect their head incase of an accident.

Racing helmets are madeof three main parts. Thehard outer shell iscoated with a composite

of carbon, glass andKevlar. Kevlar is an extremely

tough polymer that is also usedin bulletproof vests. A foam liner

made either of polystyrene or polypropy-lene is underneath this layer, and is found inthe crown of the helmet. The form-fitting innerliner is composed of either nylon or Nomex, afire-resistant material. Nomex is also used infirefighters gear and will not burn even ifsoaked in gasoline! The chinstraps are madeof Kevlar, and the visor is made from Lexan.All helmets are designed to withstand 300 Gsof force.

Drivers are held in place with a five-pointharness, similar to that found in a childs carseat. The seats hug the body and are custommade for each driver. They protect the driversrib cage during an accident. Some seats wraparound a drivers shoulders as well.

After the tragic death of legendary driverDale Earnhardt in the 2001 Daytona 500,NASCAR mandated the use of a head andneck support (HANS) device to further protectthe driver. Earnhardt died due to a fracture atthe base of the skull after a 180 mph head-oncollision into the wall during the last lap of

the race. Earnhardts death could possiblyhave been prevented if he had been wearingsuch a device.

The gas tankfuel cell in NASCAR ter-minologygenerally holds 22 gallons ofgasoline. It is composed of an inner elasticbladder made of a thermoplastic elastomersurrounded by an outer layer of steel. Theterm elastomer is often used interchangeablywith the term rubber. Elastomer comes fromtwo terms: elastic (describing the ability of amaterial to return to its original shape when aload is removed) and mer (from polymer, inwhich poly means many and mer meansparts). The tank is filled with polyurethanefoam, which prevents the fuel from sloshingaround. In case of an explosion, the foamwould absorb some of the impact. In case acar does burst into flames, the driver is pro-tected. All drivers wear fire-retardant longunderwear, as well as a fire-resistant jumpsuitand gloves made from Nomex.

Most cars are equipped with a coolingsystem that blows cool air into the drivershelmet and over his body. Sometimes, dry ice(solid carbon dioxide) is used in the car,which greatly increases the rate of cooling ofthe air flowing over it. This constant stream ofair cools the driver through the endothermicprocess of evaporation. Evaporation of waterabsorbs energy, so when sweat evaporates, itremoves energy from the skin, creating acooling effect. Sweating does not cool you if itcannot evaporate, explaining why it feels souncomfortable during days of high humiditywhen little evaporation can occur because theair is already saturated with water vapor.Without these cooling systems, temperaturescould easily reach 150 F (66 C) within a carduring a race.

The engineThe soul of every NASCAR car is its

engine. NASCAR cars have 8 cylinders, as dothe largest and most powerful passenger vehi-cles. A cylinder is a space within an enginewhere the piston moves up and down. Youcan tell how many cylinders an engine has bythe number of spark plugs. Each cylinder con-tains one spark plug. If the 8 cylinders arearranged in a V pattern, the engine is a V-8

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(which has nothing to do with the vegetablejuice). The V shape is designed to reduceengine vibration, as the vibrations that the pis-tons produce are cancelled out throughdestructive interference. The V shape maxi-mizes this destructive interference, thusreducing engine vibration.

The volume of each cylinder is known asits displacement. You may recall from yourgeometry class that the volume of a cylinder isfound by the formula V = r2h. By adding upthe total volume of all the cylinders in the car,the total displacement of the engine is deter-mined, which is commonly referred to as theengine size. A typical NASCAR car has anengine displacement of anywhere from 5735cc to 5867 cc (350 to 358 cubic inches). Thatmeans each cylinder has a displacement of717733 cca little smaller than a 1-L bottle.

1 cubic centimeter = 1 cc = 1 cm3 = 1 mL

Within each cylinder is a piston, which isa rounded piece of cylindrical metal speciallyfitted to move up and down rapidly within thecylinder. As the cylinder moves upward, anygases within the cylinder are compressed. Asthe cylinder moves downward, the gaseswithin the cylinder expand. Boyles Law statesthat as the pressure on a gas increases, itsvolume decreases, and likewise as the pres-sure on a gas decreases, its volume increases.

Attached to a piston is a connecting rod,which is attached to the crankshaft. Thecrankshaft rotates very quickly. So the up-and-down motions of the pistons are con-verted into the rotational motion of the

crankshaft, which is what ultimatelycauses the tires to spin. The faster thepistons move up and down, the fasterthe crankshaft rotates. And the faster thecrankshaft rotates, the faster your cargoes. So to get a 3400 lb (1545 kg)NASCAR race car up to a speed of 200mph (321 kilometers per hour), thosepistons must be moving up and downvery fast.

Burn, baby burnWhat causes the pistons to move up

and down within the cylinders? Thatswhere chemistry comes into place. Amixture of fuel and air within each cylin-der is ignited by a spark from the sparkplug. As the fuel combusts, it undergoesa chemical reaction, yielding gaseousbyproducts. Gasoline can only burn if it isin the vapor state; technically, liquid gaso-

line doesnt burn, it is the vapor above the liq-uid that burns. The chemical equation for thecombustion of the octane within gasoline is asfollows:

2 C8H18(g) + 25 O2 16 CO2(g) + 18 H2O(g)

The reaction is also highly exothermic,causing these gases to expand greatly. Thisexpansion pushes against the piston, causingit to move downward. Each of the followingeight cylinders will then fire, and once all eightcylinders fire, the process repeats itself overagain. These cylinders fire hundreds of timesper minute, in rapid succession. NASCAR carsdo not have a muffler, explaining why they areso loud. If the exhaust has to pass through a

muffler, it takes longer to exit the car, reduc-ing the amount of power.

Dont come knockingWhat type of fuel do these engines use?

Unlike Indy race cars, which use puremethanol (CH3OH), NASCAR race cars usegasoline, but not the same type that your caruses. They use leaded 110-octane gasoline.The lead is in the form of a compound knownas tetraethyl lead (Pb(CH2CH3)4), whichreduces engine knocking. Knocking is theloud, metallic clanging that accompaniespreignition of fuel in the cylinders before theproper time. Under certain conditions, as gasis compressed in the cylinder, it may ignitebefore the spark plug fires. A small amount ofPb(CH2CH3)4 improves the performance of thegas, preventing it from igniting as it is com-pressed. Before the 1970s, almost all of thegas in the United States was leaded, but

Pb(CH2CH3)4 is now outlawed in the UnitedStates and many other countries as a gasolineadditive because it is an environmental conta-minant that has been linked to a wide range ofneurological and other disorders (ChemMat-ters, 1983 Vol. 1(4)). NASCAR officials haveannounced a plan to switch to an unleadedhigh octane formulation by 2008.

The octane rating you see posted on agas pump such as 93 Octane or 87 Octane isdetermined by a formula that represents theaverage resistance of the gas to engine knock.Another way to look at it is the rating tells youhow much the fuel can be compressed beforeit will spontaneously ignite. The higher theoctane rating, the more gas can be com-pressed in the cylinders before ignition. The

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Eight-cylinder V8 engine.

An average pit stop involving the changing of all four tires and a full tank of fuel can take between 13and 15 seconds.

NASCAR

more fuel is compressed, the more fuel isburned per unit time, which means moreenergy is released, and that means more power!

Octane, C8H18 (sometimes called n-octane or normal octane), is a hydrocarbonthat can be compressed fairly well withoutigniting. Isooctane, an isomer of octane, iseven better at being compressed withoutigniting, so it is used in regular gasoline and is given the value of 100 in the octane ratingsystem.

The other major component of gasolineis n-heptane, and it is assigned an octane rat-ing of 0. An octane rating of 87 means themixture has the same resistance to preignitionor that it will burn as rapidly as a mixture of87% isooctane and 13% n-heptane.

Why does isooctane resist preignitionbetter than octane? Well, isooctane is a morestable compound than octane, so the com-bustion of isooctane requires greater activa-tion energy than for n-octane. Therefore,isooctane is less likely to ignite due toincreased pressure alone.

So how in the world can race cars usea fuel with an octane rating of 110? Doesthis mean you can have 110% isooctane inyour fuel? That would be impossible! Thishigh octane rating refers to the performanceof the gasoline compared to 100% octane.110-octane fuel gives a performance 10%better than fuel containing 100% octane byusing a high percentage of isooctane and acombination of other additives, includingtetraethyl lead.

TiresTires play an integral role in any

NASCAR race. A typical car can go through40 tires in one race! The tires are very thinonly about a quarter of an inch thick. If theywere any thicker, they would get too hot dueto friction between the tire and the track andwould melt. Another difference betweenthese tires and normal passenger tires is thatNASCAR tires have no tread. They are com-pletely smooth. The smooth surface means

more surface area is in contact with the road,producing better traction. The tires actuallybecome so hot that they do meltslightly, becoming sticky, whichfurther increases traction.

The tires are oftenunderinflated when they arefirst installed on a car, andafter a few laps, the tires heatup and the pressure becomesgreater. Tires can experiencean increase in pressure of1020 psi (pounds per squareinch) during a race! This is in accordance withGay-Lussacs Law, which states that the pres-sure of a gas increases as its temperatureincreases. As the temperature goes up, thekinetic energy of the particles increases,which increases the number of collisions andthus the pressure. Even when hot, the tireswill generally be under lower pressure thanyou will find on a typical passenger car, so asto increase the surface area of the tire in con-tact with the road, further increasing its grip.Because the tires have no tread, a typicalNASCAR race cannot be held in the rain or thecars would have no traction whatsoever.

Another difference between NASCARtires and normal tires is that NASCAR tires arefilled with nitrogen, not normal air (QuestionFrom the Classroom, ChemMatters February2006). Compressed nitrogen contains lessmoisture than normal air. As the tires becomeheated during the race, any moisture in thetire can vaporize and expand, causing anoticeable increase in tire pressure. Changesin tire pressure can greatly affect the handlingof a car. Using normal air that has been driedis another way to reduce moisture content inthe air, but this is more difficult to accomplish

than just using compressed nitrogen. Despitethese precautions, blowouts do occur. To pre-vent cars from careening out of control duringa blowout, most NASCAR tires contain aninner liner than allows the car to make a con-trolled stop.

And the winner is When the checkered flag lowers and the

race is over, the winner will invariably thankhis entire team for winning the race. Behindevery driver is a successful crew. The chem-istry between the driver and his crew is everybit as important as the chemistry that goes onunder the hood.

ChemMatters, FEBRUARY 2007 7

n-heptane (C7H16)

REFERENCESBurt, William. Behind the Scenes of NASCAR

Racing. Motorbooks International: St.Paul, MN, 2003.

Miller, Timothy and Milton, Steven. NASCARNow. Firefly Books, Inc.: Buffalo, NY,2004.

Van Valkenburgh, Paul. Race CarEngineering and Mechanics. Paul VanValkenburgh: Seal Beach, CA, 2000.

OTHER REFERENCES CAN BE FOUND INTHE TEACHERS GUIDE FOR THIS ISSUE.

Brian Rohrig teaches at Jonathan Alder HighSchool in Plain City, OH. His most recentChemMatters article, Thermometers, appeared inthe December 2006 issue.

n-octane (C8H18) isooctane (C8H18)

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Average Life: 150 mi Average Life: 50,000 mi

Teacher's GuideTable of ContentsQFTCNASCAR Chemistry on the Fast TrackThe Sun Fusion at WorkChemHistory: Alice BellChem.matters.links