NARRATOR: Daytona International Speedway is a 2.5 mile
track. So why are all the cars only inches apart?
And if you got hit from behind while going 200 miles an hour,
would you thank the driver who did it?
If you understood aerodynamics, you probably would.
The roar of the engines, the squeal of the tires,
then the race to victory lane. It all says, NASCAR.
A race car is much more than steel, gas, rubber and speed.
A race car is a science experiment on wheels.
DIANDRA LESLIE-PELECKY: It's hard to imagine that air
matters much to a speeding race car. But the billions
and billions of air molecules hitting the car really do make
a big difference. Sometimes air helps the car by pushing the
tires into the track and creating grip. But other times,
air is the enemy. And that can be a real drag.
PATRICK CANUPP: Drag is a bad thing because it basically
acts against the motor, and it hurts you as far as fuel
efficiency goes, and it hurts you in terms of speed,
top-end speed.
STEVE LETARTE: Roll your window down and stick your hand out.
That force on your hand trying to pull it back towards the back
of the car, that's drag. That's how much physical
drag you have on your hand.
JOHN PROBST: You got lower pressure on the back side,
higher pressure on the front side, so it just wants to push your
hand back. Drag is essentially that back pressure,
if you will, on the car.
DIANDRA LESLIE-PELECKY: Compare the force you feel when
you hold your hand perpendicular to the ground,
to the force you feel when you hold your hand parallel to the
ground. When your hand is parallel, it has to push fewer
air molecules out of the way, so there's less drag. Less drag is
a good thing. Rough surfaces and anything that sticks out
from the car increase drag. That's why there are no
side-view mirrors like there are on passenger cars.
The mirrors are placed as far inside the car as possible.
And rough surfaces, like grills, are taped.
JOSH BROWNE: We're no longer passing air through a grill,
through a radiator, which has a lot of resistance and
friction. We put the tape on the grill, most of the air just goes
up and over the car. From an aerodynamic standpoint it's the
best thing we can do. Reduces drag. The tradeoff is that
it heats up the engine, and eventually that's bad.
DIANDRA LESLIE-PELECKY: But four times a year teams pay
much more attention to drag than they do the rest of the season.
That's when NASCAR visits the two longest tracks on
the circuit. Daytona and Talladega.
PATRICK CANUPP: At those race tracks, the banking is tremendous.
You can get around the track very quickly at a very high speed.
DIANDRA LESLIE-PELECKY: To keep speeds in the safe range,
NASCAR requires cars to use an engine restrictor
plate at Daytona and Talladega.
PATRICK CANUPP: If we took our normal Charlotte car to
Daytona it would probably run 215 miles an hour.
DIANDRA LESLIE-PELECKY: The team brings a car with as little
drag as possible. The drivers have invented their own way of
compensating for the limited horsepower. Drafting.
BRIAN VICKERS: I love drafting. To be at 200 miles an hour
with 43 guys around you, and you're just beating each other
down the straightaways. And sometimes in the corners.
DIANDRA LESLIE-PELECKY: When two cars are far apart, each
car has to push air molecules out of its way, and each car is
pulled backward by the low pressure region created by its wake.
Now imagine what happens when the two cars get close to each other.
By close, I don't mean a few feet. I mean a few inches.
When two cars get close enough, air flows around them as if
they were a single car. This decreases the total amount of drag
on the two cars because one car is pushing the air molecules out of
the way for both cars. The first car doesn't generate as much of
a wake either, because the second car is so close behind it.
The end result is that the second car gets pulled
along with the first car, and they both go faster.
BRIAN VICKERS: If you could put two engines in one car,
that's two cars drafting. You know, because one car
is still only pushing the air.
DIANDRA LESLIE-PELECKY: Two cars drafting can go three
to five miles an hour faster than either car can go on its own.
Drafting is most beneficial at Talladega and Daytona
because of the restricted engine power. But you'll
see drafting at high-speed tracks like Indianapolis and Michigan,
too. Driving a few inches from each other, going 200
miles an hour, just wasn't enough for some drivers. The
desire for speed quickly turned drafting into bump-drafting.
BRIAN VICKERS: Well it feels like bumping at 200 miles
an hour. I mean, I know that's a pretty dulled down version.
But it's pretty exhilarating.
JEFF GORDON: There's some times I look up in my mirror
and I go, oh boy, this one, I'm gonna feel this one and I
hope it doesn't spin me out.
Because sometimes it can be a really abrupt impact.
DIANDRA LESLIE-PELECKY: When two cars are drafting,
the second car doesn't have to break its own hole in the air,
which means the second car has a little unused engine power.
When the trailing driver steps on the gas he speeds up and hits
the rear bumper of the first car, transferring speed to the car
in front. The whole point of racing is being the fastest.
So why would a driver help another car go faster?
BRIAN VICKERS: Self benefit. Only and surely self benefit.
If two cars are faster than one, it doesn't matter which one
of the two I am. I wanna be one of the two, and we're gonna
go forward. And then once you get to the front,
then you pass for the lead.
JEFF GORDON: And as the race gets closer and closer to
the end, taps become bumps and become hits and become
slams. And it's just, bam-bam-bam! And you really feel it.
DIANDRA LESLIE-PELECKY: People say that Dale Earnhardt
Senior was so good at drafting because he could see the air.
Dale Junior is pretty good, too, with seven of his eighteen
wins coming at Daytona or Talladega. But even if you don't
have any Earnhardt genes, you can still see the air too,
if you know the science of drafting.
