CMatter09.06

As the green flag descends,

43 cars emblazoned with

multicolored decals acceler-

ate to race speed amid the

deafening roar of thousands

of fans. The smell of rubber

permeates the air as the dri-

vers immediately jockey for position. Only one driver will

emerge victorious when the checkered flag lowers a

few hours and several hundred miles later.

Welcome to NASCAR—the uniquely Ameri-

can sport. NASCAR stands for the National

Association for Stock Car Auto Racing, and it

began in 1947. NASCAR has exploded in pop-

ularity in recent years. It is a dangerous and

exhilarating sport. The cars are loud and

fast. The drivers are as popular as movie

stars. And underneath the hood of every

car, chemical reactions are occurring

at a furious pace.

The drivers and mechanics

who work daily with these cars

thoroughly understand the

science behind them. And to

make things even more chal-

lenging, the rules change con-

stantly, sometimes weekly.

These constant rule changes

force race teams to modify their

cars accordingly. And on top of

that, each NASCAR track is dif-

ferent, creating the need for

adjustments to be made to the car, depending on the challenges of

each 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 of

steel tubing—some 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 tubing

the thinnest and designed to crush in case of a collision. This protects

the driver, as the collapsible frame absorbs the bulk of the energy of a

collision, as opposed to the driver. The frame is also designed to force

the engine downward and onto the ground in case of a severe collision,

and not into the driver.

Every NASCAR car has a few stock parts—hence the name stock

car—but these are strictly cosmetic. A stock part is a part that is made

in an assembly line by the manufacturer. The only stock parts are the

hood, 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, or

Dodge Charger. Beyond that, the cars bear little resemblance to their

namesakes.

A NASCAR car contains no glass, no doors, no back or passenger

seats, no headlights, no brake lights, no speedometer, no gas gauge,

no muffler, no stereo, no air conditioning, no glove compartment, no

horn, and no air bags! Instead of headlights, stickers are affixed to the

front of the car to resemble its parent stock car. The steering wheel is

detachable, making it easier to enter and exit the car. You do not need

a key to start a NASCAR race car—you simply flip a switch and the

engine roars to life.

Playing it safe

Safety is paramount in the construction of every feature of a

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

http://chemistry.org/education/chemmatters.html

THE UAW-DAIMLERCHRYSLER 400 NASCAR NEXTEL CUP SERIES RACE AT LAS VEGAS MOTOR SPEEDWAY. GETTY IMAGES FOR NASCAR

4 ChemMatters, FEBRUARY 2007

The Science of NASCAR

Drivers,

star

t your

engines!

By Brian Rohrig

ChemMatters, FEBRUARY 2007 5

extremely

durable material. It is so soft that it can

be easily dented or scratched, but it will not

shatter. It is covered with layers of thin adhe-

sive transparent film to prevent it from being

damaged during a race. If a layer of film

becomes scratched or dirty during the race,

it can be quickly peeled off during a pit stop.

Lexan is made from a thermoplastic polymer

known as polycarbonate. Thermoplastics

soften upon heating. Lexan is also used to

make iPods, CDs, and DVDs, and the sturdy

water bottles used by hikers. It is so strong

that it is the chief component of bulletproof

glass!

On the driver’s side is nylon webbing in

place of a window, which is designed to keep

the driver’s hands and arms inside the car

during a collision. It is equipped with a quick-

release mechanism in case a quick exit from

the car is required.

All drivers

must wear a helmet,

which is specially

designed for them,

and is designed to

protect their head in

case of an accident.

Racing helmets are made

of three main parts. The

hard outer shell is

coated with a composite

of carbon, glass and

Kevlar. Kevlar is an extremely

tough polymer that is also used

in bulletproof vests. A foam liner

made either of polystyrene or polypropy-

lene is underneath this layer, and is found in

the crown of the helmet. The form-fitting inner

liner is composed of either nylon or Nomex, a

fire-resistant material. Nomex is also used in

firefighters’ gear and will not burn even if

soaked in gasoline! The chinstraps are made

of Kevlar, and the visor is made from Lexan.

All helmets are designed to withstand 300 Gs

of force.

Drivers are held in place with a five-point

harness, similar to that found in a child’s car

seat. The seats hug the body and are custom

made for each driver. They protect the driver’s

rib cage during an accident. Some seats wrap

around a driver’s shoulders as well.

After the tragic death of legendary driver

Dale Earnhardt in the 2001 Daytona 500,

NASCAR mandated the use of a head and

neck support (HANS) device to further protect

the driver. Earnhardt died due to a fracture at

the base of the skull after a 180 mph head-on

collision into the wall during the last lap of

the race. Earnhardt’s death could possibly

have been prevented if he had been wearing

such a device.

The gas tank—fuel cell in NASCAR ter-

minology—generally holds 22 gallons of

gasoline. It is composed of an inner elastic

bladder made of a thermoplastic elastomer

surrounded by an outer layer of steel. The

term elastomer is often used interchangeably

with the term rubber. Elastomer comes from

two terms: elastic (describing the ability of a

material to return to its original shape when a

load is removed) and mer (from polymer, in

which poly means many and mer means

parts). The tank is filled with polyurethane

foam, which prevents the fuel from sloshing

around. In case of an explosion, the foam

would absorb some of the impact. In case a

car does burst into flames, the driver is pro-

tected. All drivers wear fire-retardant long

underwear, as well as a fire-resistant jumpsuit

and gloves made from Nomex.

Most cars are equipped with a cooling

system that blows cool air into the driver’s

helmet and over his body. Sometimes, dry ice

(solid carbon dioxide) is used in the car,

which greatly increases the rate of cooling of

the air flowing over it. This constant stream of

air cools the driver through the endothermic

process of evaporation. Evaporation of water

absorbs energy, so when sweat evaporates, it

removes energy from the skin, creating a

cooling effect. Sweating does not cool you if it

cannot evaporate, explaining why it feels so

uncomfortable during days of high humidity

when little evaporation can occur because the

air is already saturated with water vapor.

Without these cooling systems, temperatures

could easily reach 150 °F (66 °C) within a car

during a race.

The engine

The soul of every NASCAR car is its

engine. NASCAR cars have 8 cylinders, as do

the largest and most powerful passenger vehi-

cles. A cylinder is a space within an engine

where the piston moves up and down. You

can tell how many cylinders an engine has by

the number of spark plugs. Each cylinder con-

tains one spark plug. If the 8 cylinders are

arranged in a “V” pattern, the engine is a V-8

O C

isophthaloylchloride

meta-phenylenediamine

NOMEX meta-aramid[poly(meta-phenyleneisophthalamide)]

Synthesis of NOMEX

MIKE CIESIELSKI

NASCAR

Cockpit showing head and neck support device.

NASCAR

6 ChemMatters, FEBRUARY 2007

(which has nothing to do with the vegetable

juice). The V shape is designed to reduce

engine vibration, as the vibrations that the pis-

tons produce are cancelled out through

destructive interference. The V shape maxi-

mizes this destructive interference, thus

reducing engine vibration.

The volume of each cylinder is known as

its displacement. You may recall from your

geometry class that the volume of a cylinder is

found by the formula V = πr

h. By adding up

the total volume of all the cylinders in the car,

the total displacement of the engine is deter-

mined, which is commonly referred to as the

engine size. A typical NASCAR car has an

engine displacement of anywhere from 5735

cc to 5867 cc (350 to 358 cubic inches). That

means each cylinder has a displacement of

717–733 cc—a little smaller than a 1-L bottle.

1 cubic centimeter = 1 cc = 1 cm

= 1 mL

Within each cylinder is a piston, which is

a rounded piece of cylindrical metal specially

fitted to move up and down rapidly within the

cylinder. As the cylinder moves upward, any

gases within the cylinder are compressed. As

the cylinder moves downward, the gases

within the cylinder expand. Boyle’s Law states

that as the pressure on a gas increases, its

volume 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. The

crankshaft 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 ultimately

causes the tires to spin. The faster the

pistons move up and down, the faster

the crankshaft rotates. And the faster the

crankshaft rotates, the faster your car

goes. So to get a 3400 lb (1545 kg)

NASCAR race car up to a speed of 200

mph (321 kilometers per hour), those

pistons must be moving up and down

very fast.

Burn, baby burn

What causes the pistons to move up

and down within the cylinders? That’s

where chemistry comes into place. A

mixture of fuel and air within each cylin-

der is ignited by a spark from the spark

plug. As the fuel combusts, it undergoes

a chemical reaction, yielding gaseous

byproducts. Gasoline can only burn if it is

in the vapor state; technically, liquid gaso-

line doesn’t burn, it is the vapor above the liq-

uid that burns. The chemical equation for the

combustion of the octane within gasoline is as

follows:

2 C

18(g)

+ 25 O

➞ 16 CO

2(g)

+ 18 H

(g)

The reaction is also highly exothermic,

causing these gases to expand greatly. This

expansion pushes against the piston, causing

it to move downward. Each of the following

eight cylinders will then fire, and once all eight

cylinders fire, the process repeats itself over

again. These cylinders fire hundreds of times

per minute, in rapid succession. NASCAR cars

do not have a muffler, explaining why they are

so loud. If the exhaust has to pass through a

muffler, it takes longer to exit the car, reduc-

ing the amount of power.

Don’t come knocking

What type of fuel do these engines use?

Unlike Indy race cars, which use pure

methanol (CH

OH), NASCAR race cars use

gasoline, but not the same type that your car

uses. They use leaded 110-octane gasoline.

The lead is in the form of a compound known

as tetraethyl lead (Pb(CH

)

), which

reduces engine knocking. Knocking is the

loud, metallic clanging that accompanies

preignition of fuel in the cylinders before the

proper time. Under certain conditions, as gas

is compressed in the cylinder, it may ignite

before the spark plug fires. A small amount of

Pb(CH

)

improves the performance of the

gas, preventing it from igniting as it is com-

pressed. Before the 1970s, almost all of the

gas in the United States was leaded, but

Pb(CH

)

is now outlawed in the United

States and many other countries as a gasoline

additive because it is an environmental conta-

minant that has been linked to a wide range of

neurological and other disorders (ChemMat-

ters, 1983 Vol. 1(4)). NASCAR officials have

announced a plan to switch to an unleaded

high octane formulation by 2008.

The octane rating you see posted on a

gas pump such as 93 Octane or 87 Octane is

determined by a formula that represents the

average resistance of the gas to engine knock.

Another way to look at it is the rating tells you

how much the fuel can be compressed before

it will spontaneously ignite. The higher the

octane rating, the more gas can be com-

pressed in the cylinders before ignition. The

http://chemistry.org/education/chemmatters.html

Eight-cylinder V8 engine.

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

and 15 seconds.

NASCAR

more fuel is compressed, the more fuel is

burned per unit time, which means more

energy is released, and that means more power!

Octane, C

(sometimes called n-

octane or normal octane), is a hydrocarbon

that can be compressed fairly well without

igniting. Isooctane, an isomer of octane, is

even better at being compressed without

igniting, so it is used in regular gasoline and

is given the value of 100 in the octane rating

system.

The other major component of gasoline

is n-heptane, and it is assigned an octane rat-

ing of 0. An octane rating of 87 means the

mixture has the same resistance to preignition

or that it will burn as rapidly as a mixture of

87% isooctane and 13% n-heptane.

Why does isooctane resist preignition

better than octane? Well, isooctane is a more

stable 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 to

increased pressure alone.

So how in the world can race cars use

a fuel with an octane rating of 110? Does

this mean you can have 110% isooctane in

your fuel? That would be impossible! This

high octane rating refers to the performance

of the gasoline compared to 100% octane.

110-octane fuel gives a performance 10%

better than fuel containing 100% octane by

using a high percentage of isooctane and a

combination of other additives, including

tetraethyl lead.

Tires

Tires play an integral role in any

NASCAR race. A typical car can go through

40 tires in one race! The tires are very thin—

only about a quarter of an inch thick. If they

were any thicker, they would get too hot due

to friction between the tire and the track and

would melt. Another difference between

these tires and normal passenger tires is that

NASCAR 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 actually

become so hot that they do melt

slightly, becoming sticky, which

further increases traction.

The tires are often

underinflated when they are

first installed on a car, and

after a few laps, the tires heat

up and the pressure becomes

greater. Tires can experience

an increase in pressure of

10–20 psi (pounds per square

inch) during a race! This is in accordance with

Gay-Lussac’s Law, which states that the pres-

sure of a gas increases as its temperature

increases. As the temperature goes up, the

kinetic energy of the particles increases,

which increases the number of collisions and

thus the pressure. Even when hot, the tires

will generally be under lower pressure than

you will find on a typical passenger car, so as

to increase the surface area of the tire in con-

tact with the road, further increasing its grip.

Because the tires have no tread, a typical

NASCAR race cannot be held in the rain or the

cars would have no traction whatsoever.

Another difference between NASCAR

tires and normal tires is that NASCAR tires are

filled with nitrogen, not normal air (Question

From the Classroom, ChemMatters February

2006). Compressed nitrogen contains less

moisture than normal air. As the tires become

heated during the race, any moisture in the

tire can vaporize and expand, causing a

noticeable increase in tire pressure. Changes

in tire pressure can greatly affect the handling

of a car. Using normal air that has been dried

is another way to reduce moisture content in

the air, but this is more difficult to accomplish

than just using compressed nitrogen. Despite

these precautions, blowouts do occur. To pre-

vent cars from careening out of control during

a blowout, most NASCAR tires contain an

inner 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 thank

his entire team for winning the race. Behind

every driver is a successful crew. The chem-

istry between the driver and his crew is every

bit as important as the chemistry that goes on

under the hood.

ChemMatters, FEBRUARY 2007 7

n-heptane (C

)

REFERENCES

Burt, William. Behind the Scenes of NASCAR

Racing. Motorbooks International: St.

Paul, MN, 2003.

Miller, Timothy and Milton, Steven. NASCAR

Now. Firefly Books, Inc.: Buffalo, NY,

2004.

Van Valkenburgh, Paul. Race Car

Engineering and Mechanics. Paul Van

Valkenburgh: Seal Beach, CA, 2000.

OTHER REFERENCES CAN BE FOUND IN

THE TEACHER’S GUIDE FOR THIS ISSUE.

Brian Rohrig teaches at Jonathan Alder High

School in Plain City, OH. His most recent

ChemMatters article, “Thermometers,” appeared in

the December 2006 issue.

n-octane (C

) isooctane (C

)

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ACS STOCK ART

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NASCAR

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