(cars zooming)
- How does a Koenigsegg Regera,
a car without a transmission,
get to over 250 miles an hour?
With a torque converter.
- [Driver] Just move.
- Who's that-- what now?
How'd that car stop without stalling out?
Doesn't even have a clutch!
That's un-possible!
Well I'm gonna give you zero guesses how.
That's right, it's a torque converter.
The basic function of a transmission,
whether it's manual or automatic,
is to transfer power to the drive shaft and drive wheels
of a vehicle.
It also makes sure that the speed and torque
of the drive wheels sync with the speed of the engine
so that everything's copasetic.
In order to shift gears or come to a stop,
something has to interrupt the connection
between the constantly spinning engine
and the sometimes moving drive shaft.
If you stop the drive wheels and there's no clutch,
the engine dies.
In a manual transmission, you can engage the clutch
and that disconnects the engine shaft from the drive shaft
so the engine can spin independently.
An automatic transmission doesn't have a clutch.
It has a torque converter.
Okay, real quick, let's hit on the Koenigsegg Regera.
You know, only one of the sweetest cars on the planet.
Maybe you heard of it?
The Regera is a hybrid super car
that has 15,000 horsepower.
- What?
- That has 1,500 horsepower and can hit 250 miles an hour.
It's got a twin turbo V8 combustion engine
and three electric motors but no transmission,
so there's a combustion engine
going directly to the rear wheels.
Each output shaft of the rear wheels
gets their own electric motor,
and there's one more electric motor on the crank shaft
uses a starter, a generator, a torque adder,
a power adder, and it can be used to charge the battery.
You wanna take a guess
as to what sits between the combustion engine
and the drive unit?
Yup!
It's a torque converter.
Koenigsegg likes to call it a hydraulic coupling,
but we know what it is.
It's a torque converter.
A torque converter is a fluid coupling system.
That's a hydrodynamic device
used to transmit rotating mechanical power.
Letting the car come to a stop
while keeping the engine running
isn't all that a torque converter can do.
It's also got a secret function
that not a lot of people know about.
- [Male Voice] Spooky spooky.
- It also converts torque.
I know, right?
(applause)
Torque converter.
Torque converters multiply engine torque output,
transferring the power from the engine
to the transmission input shaft,
and they drive the pump of the transmission.
That's all pretty important stuff.
All right, so let's take a look at one of these suckers.
I know what you're thinking.
Looks like a UFO.
But most UFOs are bluish.
(crash)
This is the torque converter housing.
It's bolted to the flywheel,
so it turns at whatever speed the engine's turning.
Inside this torque converter are four main components.
We have the impeller, the stator, and the turbine,
and on newer cars, we also find a torque converter clutch.
Okay, let's start with the impeller.
It's named after the first vampire, Vlad the Impeller.
It's got fins all over it, see?
The impeller is welded
onto the inside of the torque converter housing,
so the impeller spins with the engine.
There's transmission fluid in here,
and while the impeller is spinning,
these fins catch the liquid and throw it outward.
The impeller essentially acts like a centrifuge.
I'm sure you know how fins can fling a liquid out.
You think of a blender.
A little blade spins at the bottom,
but it spins so fast, it can shoot your smoothie
all the way up the sides and out.
And that's centrifugal force.
Cen-centrifugguh vuss?
Now imagine that blender turned horizontally,
and the whole thing's spinning.
That's how the fins in the torque converter work.
Or, maybe it's more like a salad spinner
where the whole thing spins.
Well, whatever.
The next component's the turbine.
The turbine in a torque converter is loosely mounted
because it's gotta be driven.
The impeller is the driver, and the turbine gets drove.
And the turbine is splined
to the input shaft of the transmission,
so insie the torque converter,
the impeller is sending fluid out,
and that is driving the turbine,
which is then sending that liquid down to the impeller,
which sends it back to the turbine,
and so on and so on and so on and so on and so on
and so on and so on and so on and so on and s...
(wormhole sound effect)
Well anyways.
Let's say I've got two fans,
and not just because I wanna show you
that I can afford two fans,
but because we're gonna do a demonstration.
This fan is gonna be powered by electricity.
Nolan.
That's really getting going.
But look what's going on here.
The unplugged fan with no power is also moving.
All right, now I'm gonna do another trick.
I'm gonna stop this fan with my bare bart hands.
Thee?
So, the nonpowered one is stopped.
Now I'm gonna let it go.
(applause)
And it's moving again.
This is what happens when a car comes to a stop.
The impeller always has power,
because it is connected to the engine.
The impeller's supplying power to the turbine,
which is connected to the transmission,
which controls the drive shaft.
When you brake, all that stops is the turbine.
So we don't have to cut off power to the engine.
And then, when you're ready to go again,
you let off the turbine by taking your foot off the brake,
and you let it receive all that sweet sweet power.
And also, keep in mind that I can afford two fans.
That was fantastic.
Now if this was all the torque converter did,
and don't get me wrong, that's a lot!
But if it's all we did, we'd just call it a fluid coupling.
We'd also lose lots of energy
because of all that churning loss.
But we don't do that and we don't call it that.
The reason we call it a torque converter
is because that other little contraption we mentioned,
the stator.
The stator sits between the impeller and the turbine,
and that minimizes the churning loss.
You know what else it does?
It converts torque.
The stator actually increases torque output
by redirecting the fluid.
The stator blades have aggressively sharp angles.
You see how aggressive and sharp those angles are
on the blades of the stator?
You can think of the liquid being sent out of the impeller
like it's water coming out a garden hose
hitting the turbine.
But when the stator's in there and spinning,
it acts like your thumb
being placed over part of the end of that garden hose.
Now, the liquid being sent off the impeller
is shooting off those sharp angled blades,
and the stator can only move in one direction.
It's actually now making the turbine spin faster
than the impeller.
You got any idea what that's doing?
It's increasing torque!
It's a torque converter!
It's all about using viscous force,
which was also my nickname in high school.
The stator's also got this nifty one-way clutch,
so when you're at a dead stop
and the engine's turning the impeller,
it's not moving.
It only gets going when the liquid hits it,
and when the impeller and turbine
are going around the same speed,
it's now moving too, creating less resistance to liquid
because less torque is needed.
Now let's look at the torque converter clutch.
This is basically a lockup clutch.
It's the equivalent of popping it into fifth
in a five-speed manual.
It fits around the turbine
inside the torque converter housing.
Remember those two fans that I can afford?
(somber music)
The one with power blew the one without the power,
but we lost some power in the process.
That happens because the impeller drives fluid
to drive the turbine.
You're always gonna lose a bit of energy to that fluid.
But at a certain point, the fluid pressure builds up enough
and the speed of the impeller and turbine are close enough,
and that causes this clutch to lock the turbine into place
making it a part of the torque converter housing
along with the impeller.
Now you're at cruising speed,
And these springs help to dampen that shift,
just like the springs we saw on the clutch plate
in a traditional clutch.
Christian Koenigsegg said
he approached torque converter manufacturers
and nobody was interested in producing what he wanted
at a low volume, and some of them
couldn't even understand what he was trying to do.
- What is this?
- So he built his own hydraulic coupling to the extreme!
It's got crazy fins all over it.
It's super lightweight,
made entirely out of machined aluminum.
It can be opened or closed or locked up completely.
It's not needed for the vehicle to function,
but it is necessary
to attain that mindblowing acceleration.
The Regera's basically in seventh gear all the time.
When you're at a dead stop and you start to accelerate,
the electric motors are driving the rear wheels directly.
Then, between 20 and 30 miles an hour,
the combustion engine takes over.
The hydraulic coupling steps in,
and it begins that torque converter effect.
While the torque converter's increasing the torque
from the combustion engine, thanks to the turbine,
the electric motor of the crank shaft,
well, that's increasing torque as well,
and that allows the Koenigsegg Regera
to go from zero to 250 in 20 goldarn seconds.
Koenigsegg says, if you just had the combustion engine
on this car, it'd go zero to 60 in seven seconds.
Just leaving the rear wheel electric motors,
you'd to zero to 60 in four.
But the combination with the torque converter
is what allows it to go from zero to 60 in 2.8 seconds,
or as much as the wheel grip allows.
He reinvented the hybrid electric
and reimagined the old tech of the fluid coupling,
torque converter, to help do it.
Now if you'll excuse me, I gotta go buy a third fan.
Torque converters!
Thanks for watching this episode of Science Garage, guys.
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Don't tell my wife what I did with the fans.