- [Nolan] An American V8.
A 12 cylinder Italian stallion.
Or a Japanese inline 6.
Everyone's got at least one engine sound
that gets them going.
But what makes them sound different?
It's not just the exhaust pipe.
Hey James?
(door squeaks)
(upbeat dance music)
- [Man In White] Looks like Nolan got
into the Nos Energy stash again.
- [Man In Blue] Those dance classes are really
paying off though. - Sick moves.
- So many parts of the car can have an impact
on how an engine sounds.
And car companies pour millions of dollars
into developing those sounds.
Sometimes they (bleep) up.
To understand engine sound, you must first understand
the fundamentals of sound itself.
Yep, it's gonna be one of those episodes.
The reason we hear at all,
is thanks to waves of different pressures
traveling through the air.
Our ears interpret these waves as sound.
How fast the wave oscillates is called frequency
and it's measured in Hertz.
The frequency of a wave determines the pitch.
So if the wave is slower, you hear a lower pitch.
If the wave is faster, you hear a higher pitch.
That's easy, right?
You are now a certified audio engineer, like Joe.
Engine sound is produced after a cylinder fires
and sends the exhaust in the form of pressurized air
into the exhaust manifold.
These are called pulses.
And the rate of pulses per second coming out of an engine
is what dictates frequency or pitch.
Sounds are made up of a bunch of different frequencies.
(engine revs)
The frequency with the largest amplitude, or volume,
is called the dominant frequency
or root tone.
The pitch is directly linked to the revolutions per minute
which is what gives us tone change
when we're revving the engine.
(engine revs)
Everything that makes noise has a root tone,
and in the case of cars, that frequency can be calculated.
Okay this is where it starts
to get a little more complicated but
stay with me here.
I'm pretty bad at math too, but trust me,
this is how you do it.
Engine speed can be converted from revolutions per minute
to revolutions per second then to Hertz.
60 revolutions per minute
equals one revolution per second or one Hertz.
To make it easy, let's start with a V8, okay?
An eight cylinder engine idling at 1,000 RPM
should be about 17 Hertz.
But this only accounts for one cylinder.
Four stroke engines, like V8s, fire two cylinders once
every two turns of the crank shaft,
so only half the cylinders in an engine
are firing during one revolution.
Still with me, that make sense?
Great.
In a V8, because only four cylinders are firing
during one revolution,
we're gonna multiply four by 17 Hertz
giving you a dominant frequency of 68 Hertz.
This is called the fourth engine order
and it's specific to eight cylinder engines.
Take a V10 for example, one of the coolest sounding engines.
We did a bumper to bumper on the Lexus LFA.
It has one, it sounds great.
To figure out the dominant frequency of a V10
at 6,000 RPM, it's 6,000 divided by 60, 100.
Multiplied by half the amount of cylinders, five.
Which gives us a dominant frequency of 500 Hertz
at 6,000 RPM.
This formula just gets you the dominant tone
that the engine produces.
There are also quieter frequencies
that complement the sound.
These quieter tones can be caused by anything
from the resident frequency of the engine bay
to the thickness of sheet metal used in the car
or the diameter of piping used.
Much of the sound we hear from an engine
has to do with the cars exhaust system as well.
A big fart can exhaust
lets out a lot more air at one time,
which gives us a bass-ier tone.
That's why you see cars like Sentras or CR-Xs
with huge exhausts trying to beef up the sound
of their little four banger.
(engine revs)
(farting)
There are engineers at every major car company
that focus on just the sound alone.
They work in the NVH
or noise vibration harshness department.
A completely unaltered engine sound
has some abrasive tones.
These engineers experiment
with different diameter pipes, mufflers, bushings,
and other insulation material to mute
those unwanted frequencies
and shape the engine tone to the company's liking.
- [Voiceover] Computer, computer, yep, yep, yep,
yep, yep, yep, yep, yep.
- One super recognizable sound
is the good ol' American V8.
It's a really throaty, gurgley sound that everyone loves.
(engine revs)
But why does it sound so much different
than an eight cylinder European engine?
(engine revs)
- Let's ask some people at donut.
- American and European cars probably just (bleep).
- Just, probably just like different exhaust manifolds.
- The passion involved with the production.
- [Voiceover] Round two.
- Probably all the cats and all the EGR valves
and stuff like that we have to have in America.
- Probably just the firing order in which the pistons
are going up and down.
I'm a VQ type of guy.
- [Nolan] Most European eight cylinder engines
use a flat plane crank.
Which means the lobes on crank shaft
are separated by 180 degrees.
This makes the firing of the cylinders happen
in a balanced way.
Each cylinder fires from the opposite one across from it.
A very consistent and uniform firing order.
American V8's on the other hand use cross plane cranks
which have lobes at very 90 degrees from each other.
This makes the firing seem a little more sporadic
and unbalanced.
It also creates moments when two cylinders
on the same side of the block
fire at the same time producing a lower,
guttural noise which adds to the ragged sound.
(engine revs)
Sometimes the intake can form an exhaust sound
just as much as the exhaust or engine block itself.
Cars like the Lexus LFA have a two intake sound.
(engine revs)
It has surge tank under the hood
that engineers from Yamaha tuned
in order to generate the sound angels would make
if they were in cars instead of in heaven.
Not only that, they tune the exhaust as well.
How Yamaha went from making pianos to side by sides
to saxophones to building and tuning Lexus engines
I'm not really sure.
You all know that (engine revving)
of rotary engine, right?
Without getting too technical,
a rotary engine has three firings
per rotation of the Accenture shaft.
When the exhaust phase and the intake phase overlap,
some of the exhaust seeps into the intake chamber
and that's when you hear that (engine revs) noise.
It's a really distinctive and kind of polarizing sound.
I love it.
Our friend Aaron Parker has a heavily modified
RX7 drift car that I think sounds amazing.
Check out the bumper to bumper on it here.
I love rotaries, I need to get an RX7.
One engine that gets some flack for its sound
is the boxer engine.
But I just think they're being Subie haters.
This type of engine has horizontally opposed pistons
and a unique firing pattern.
Subarus are famous for having boxer engines
and same with Porsches.
But why do people love how Porsches sound
and they hate on Subarus?
The reason is because Subaru boxer engines
have unequal length headers, which means
that they exhaust coming out of cylinders one and three
has to travel a different distance
than the exhaust coming off of cylinders two and four.
This is effects the sound, producing a lower base tone
and a distinct rumble.
I love how boxers sound, I love how Subarus sound.
I think they're awesome.
The older 2.5 liter WRX STI engines
have unequal length Heathers.
Heathers, Heathers, (bleep).
Headers, headers, Heathers.
How many takes is this gonna--
The older 2.5 liter STI engine has unequal length headers.
But the new two liter WRX has equal length headers.
Which is why it sounds so much smoother.
Ever since Porsche switched from a flat six
to a turbo charged flat four,
people have started comparing the engine sound
to a Subaru.
This is because the new Boxster
also has unequal length headers,
resonators, and an asymmetrical muffler
that add to that ragged sound.
Don't believe me?
Listen to this.
(engine revs)
Of course there are a million other sounds
that come from a car's engine.
They're all music to my ears.
I could go on forever.
But we'll save that for another video.
Let us know in the comments which engine you think
sounds the best, and while you're at it,
hit that like button so we can keep making videos for you.
(jazzy upbeat music)