- What do a $1.8 million super car,
a group B rally monster,
and this tiny hundred horsepower hatchback have in common?
They're all twin charged baby.
They have both a supercharger and a turbocharger.
A true KFC double down sandwich of power.
This decades old design could be making a comeback.
So today we're going to figure out
why you would want
to double down on forced induction
and why so few cars have ever been twin charged
in the first place.
Turns out mo' charging might just mean mo' problems.
Biggie smalls, 2021.
He's still alive.
I don't know what they want from me.
It's like the mo' charging we come up
and the mo' problems we see.
(bouncy music)
Thanks to K&N for sponsoring today's video.
It's officially garage season.
Which means it's time
to start spending countless hours working
on your cars and spending a ton of money,
constructing your own upgrades like this custom air filter.
I call it the fast air recirculation transmitter.
Smoke means it's working.
- Why not just use a K&N filter,
it's way easier than that.
- I'm sorry,
but it can't be easier than this.
Air gets sucked into these dual unnecessary duct.
Gets passed to this nice multiple precise oxygen sensor down
into the elastic waste washer
and back into the box
for a farrow integrated injector.
- Yeah or you can just go to a K&N filter.
They are easier than that.
Honestly, they work way better.
And K&N was started in a garage with two dudes
in Riverside, California, 50 years ago.
So, you know their products are engineered
for people who love garage season.
They offer air filters, cabin air filters,
oil filters, air intakes, electronics, and much more.
- Sure, but do they make custom ones for your vehicle?
You know, mine's custom because I use plywood
and I use my grandma's fan for it.
- Yeah K&N actually designs these
to custom fit specific makes and models
and their upgrades are designed to be easy to install,
to make your car run faster,
run further and run cleaner.
And we use K&N filters on a bunch of our donut cars
and even on our personal cars.
It's what I was running on my S14 back when it ran.
So head over to knfilters.com/donut
for some special discounts today.
- All right.
I'll admit I'm impressed,
but this K&N have an oil hub filter utilization contraption?
- Yeah, as I said, just seconds ago,
they make oil filters.
Here, this one's for you.
- You really have thought of everything.
1985 saw the NBA debut of Michael Jordan,
the original Nintendo hit US shores
and the first production engine
to use both a turbocharger and supercharger
was put in a car,
which is 1.8 liters of displacement.
That engine made 500 horsepower
and was in the Lancia Delta S4.
It won five out of the 12 WRC rallies
that entered in that year.
And the 35 years since then
there have been just eight twin charge production engines,
but three of those have debuted since 2018.
But why would you need both a turbo and a supercharger?
Why not just have a twin turbo or a twin supercharger?
Does that even exist?
Well, to understand why there are so few twin charge engines
and why we may be seeing more on the horizon,
we first need to understand what forced induction does
and why you would use it in the first place.
Every internal engine needs a healthy diet of air
and there are two ways to get it.
Some engines are naturally aspirated,
these other almighty, but gentle whale sharks,
drifting along lazily scooping up air,
but others, they use forced induction.
These are like great whites charging around the seeds,
gobbling up as much air as they can
to feed their ceaseless hunger.
That extra air is forced like this shark analogy.
We could have chosen anything else,
but we chose the animals in the water.
Doesn't matter.
Okay, now it's forced into the engine
by an external compressor,
which raises the density of the intake charge.
Intake charge is the mixture of air
and fuel entering the cylinders.
The amount of oxygen
in the charge determines
how much fuel an engine can combust.
The air entering a naturally aspirated engine
has the same density as the atmosphere around it
with natural aspiration the only way to get more air
into cylinders is to increase their volume,
known as displacement.
But with forced induction,
a compressor raises the intake air density,
creating supercharged air with more oxygen by volume.
The amount the air density increases is the boost pressure
combine boost with more fuel,
and that means bam, embryo, like glacey more power.
In other words,
by increasing the density of the air,
you can burn more fuel without needing a larger engine.
Exactly what you want,
if you're designing a car
with the limit on engine displacement,
like they have in the WRC,
or if you want the fuel economy
and emissions of a small engine,
but with more power.
Now, the two most common compressors
are turbochargers and superchargers.
Each have benefits and drawbacks
and twin charging uses the advantages of one of those
to make up for the drawbacks of the other.
So to understand how they can work together,
we need to look at the biggest difference between them,
how they're powered.
A turbocharger uses the engines exhaust as a power source,
exhaust gas spins a turbine,
which is attached to an impeller.
Impeller draws more air into the engine's intake
to create boost.
And the bigger the turbo is,
the more boost it can make,
but turbos, especially big turbos
have a couple of drawbacks.
One of them is heat like me when I'm on the dance floor,
cue me dancing on the dance floor.
You see how hot I get.
Increasing intake pressure also increases temperature
and hot air has less oxygen by volume than cold air.
Since the whole point of a turbo
is to increase the amount of oxygen in the intake charge.
Many turbo systems will include an intercooler,
which works like a radiator.
The charged air is routed through a metal panel
with lots of fins.
All that surface area transfers heat
from the pressurized air to the atmosphere.
That's great for lowering intake temperature,
but it increases the complexity and weight
of the turbo system.
It also adds internal volume to the intake.
Filling that extra space with pressurized air takes time.
That creates a power delay from when you mash accelerator
as boost pressure built into the system,
something referred to as turbo lag.
Oh you got turbo lag dude.
Dude I never had a turbo lag.
I don't know what you're talking about.
Now lots of times turbo lag is confused
with something called boosts threshold.
That's the minimum speed
at which there's sufficient exhaust pressure
to spin the turbo fast enough to create boost.
With a small turbo,
the boost threshold can be as low as 1500 RPM,
but bigger turbos might require engine speeds
of 4000 RPM or more.
The turbine itself will be spinning 10 to 30 times faster
than the engine.
And some turbos can reach speeds over 280,000 RPM.
That's like this fast.
Generally bigger turbos make more boosts,
but with a higher boost threshold.
It takes power to push exhaust past the turbine
and below the boost threshold,
the turbo actually reduces the amount
of power being sent to the wheels.
So how do you deal with something like that?
What do you do?
Oh one way is to add another force induction device
that isn't powered by exhaust pressure.
And in that case, that's a supercharger.
You can power a supercharger with electricity,
but that's pretty uncommon
because it comes with its own set of problems.
We made an entire episode about it,
check it out here
if you want to know more.
Instead of electricity or exhaust gases,
a typical supercharger gets power
from the rotation of the crank.
And there are three common types.
You've got a centrifugal, you've got a roots,
you've got a twin-screw.
Centrifugal superchargers operate a bit like a turbo,
but replace a turbine with a pulley driven by the crank.
Like a turbo, these have a boost threshold,
typically needing an impeller speed of 30,000 to 60,000 RPM.
To achieve that,
centrifugal superchargers use a set of gears
to multiply the crank's rotation.
That means as crank speed increases,
there's an exponential increase in impeller speed,
but below the boost threshold,
they simply aren't spinning fast enough to do anything.
And that means a centrifugal supercharger won't make up
for a turbo's lack of low RPM punch.
Pop, pop, pop.
So for twin charging,
you need a roots or twin-screw supercharger
because both are positive displacement superchargers.
That means they flow the same amount of air
for every rotation of the crank
from idle all the way to red line.
And that means no boost threshold.
Because these superchargers are pumping the same amount
of air regardless of engine speed,
they can be measured by their displacement,
just like an engine.
So two liter roots or twin-screw supercharger
moves two liters of air for every rotation of the crank.
A roots supercharger uses two rotors
with three or more lobes
that mesh together as they rotate in opposite directions.
The space between the lobes is filled with air
on the inlet side of the supercharger,
and that air gets forced out on the discharge side,
into the intake manifold.
The air isn't compressed inside of the supercharger itself.
It's simply blown by the compressor into intake.
So these are sometimes called blowers.
Roots blowers are simple and reliable,
but they have some drawbacks as well.
They tend to be heavy,
produce a lot of heat and take up a lot of space.
Because they're driven by the crank,
they're also parasitic like that worm in my belly,
drawing power from the engine to spin the rotors.
Those rotors also don't seal perfectly.
So air leaks between them
and that inefficiency reduces boost pressure.
Twin screw superchargers use two screw shape rotors
with a male and female side that mesh more completely
than the rotors in the roots blower,
meaning fewer air leaks.
Those screw rotors also compress the air inside
of the supercharger itself.
Meaning they're more efficient than a roots.
They're also smaller and lighter,
but because of their tighter tolerances,
they require more precision to manufacture.
And they're usually more expensive.
Since they always provide the same volume of extra air
with every rotation of the crank,
the extra power from a positive displacement supercharger
is available at idle.
But the big problem is they can never make any more boost
than that.
And they can't reach the same peak output
that a turbo can.
A turbo will be more capable at high reps,
but at the cost of low-end power below the boost threshold.
So at this point,
you guys figured out
why you might want to use both of these.
You get the best of both worlds.
Supercharger can add boosts from idle
up to the turbos boost threshold,
and then the turbo can take over to make even more power
all the way up until redline.
The supercharger can also fill in for the turbo
while it's spooling up to reduce turbo lag.
So twin charging is the best of both worlds.
But like everything that seems to be great
as you're approaching it with that analytical mind,
there are some problems.
First problem is I need to go real quick
to change my underpants cause I let something out
and I left fart out and something came out.
What are some of the actual problems?
Well, you've probably already guessed
what some of those might be
because we talk about them in nearly every episode of B2B,
when we're discussing some new piece of technology.
Mass, complexity and the cost.
A turbo requires a bunch of extra stuff under the hood.
You need a complicated exhaust manifold.
You need extra intake plumbing for the intercooler,
which needs to be placed somewhere
that isn't getting cooked by the engine
and the turbo itself.
That all takes up space and it adds weight.
Adding a supercharger does the same thing.
You need an extra pulley and a belt coming off the crank.
The supercharger is usually mounted
right on top of the engine, increasing its height.
And if you want to cool that air,
you're probably going to have to mount the intercooler
in the worst place possible,
directly between the motor and the supercharger.
That means running lines for liquid cooling.
So using both types of force induction
means those systems have to work together.
Twin charge incidents
have two partially overlapping intake pass,
complete with sensors to detect air flow in both
and an ECU program to switch between the systems
that requires a clutch to disengage the supercharger pulley
at high revs and solenoids and valves to seal the part
of the intake where the turbo takes over.
That's one reason
why so few D-holes twin charge their engine.
Well, if you're D-hole,
you're part of the donut underground
our members only subscription-based service,
you get a bunch of extra content.
You get shirts, you get stickers.
Click that join button right below.
You can even get in the discord chat with me.
I'm a fellow D-hole.
What's up my D-holes, D-hole, D-hole, D-hole.
And the other big reason is the cost.
Volkswagen made one of the few mass produced
twin charged engines with their 1.4 liter TSI.
They put it in the Golf, Jetta
and many other small cars as a replacement
for a two liter naturally aspirated engine.
The result was more power, more torque, less weight,
better acceleration,
better fuel economy and reduced emissions.
Earning Volkswagen numerous engine design awards
between 2006 and 2011.
But then the accountants figured out that getting rid
of the supercharger would save them over 10 million bones.
Replacing it with an engine that was turbo only
wasn't that much worse.
So you got the axe.
There have been just eight production engines
that have been twin charged in the history of engines.
It's not very many
because there's a lot of engines out there.
I guess if it was a good idea,
everyone would be doing it.
But three of those eight have appeared
in the last three years.
Audi, Land Rover and Mercedes have all recently jumped
on the twin charging bandwagon.
What makes this new generation of twin chargers interesting
is that the supercharger is electric.
This is a musical episode.
The problem with electric superchargers
has always been providing enough electricity
to make them spin fast.
The Audi, which is a twin charged diesel
needs a special electrical system,
just for the supercharger.
But the Land Rover and the Mercedes
have an internal combustion engine
and a hybrid system with big batteries
to power electric motors,
and more than enough for electric supercharging too.
Combined those systems are good for around 400 horsepower.
So I guess twin charging ain't dead just yet
until electric completely kills the engine part
of that twin charged engine.
(melancholy music)
- Hey friend, I know where you're at.
You forgot to get a gift for the donut fan in your life,
and it's too late or anything to be shipped.
Well, you're in luck because donut media gift cards
are a thing
and you can get them in some phenomenal increments.
I'm talking $25, $50, $75,
$100, $150.
And if you wanted to do something crazy, like $7,500,
give me a call and we'll work something out.
The donut media gift cards are 100% digital.
They don't rely on old school, guy on a horse,
delivering things,
which is how I assume things still get to people.
And each of them are designed after an 80s credit card,
which is a genius idea that I came up with
in literally three seconds.
So head on over to donutmedia.com
and pick up your perfect stocking stuffer today.
- Thank you guys so much for watching this episode of B2B.
What do you think you guys got any homegrown,
homemade twin charging systems out there?
Leave a comment down below.
Let me go see, I'll go.
I'll go Google it.
I'll go search for it.
If you could please hit that Like and subscribe button
that lets us know that we're doing good.
I don't know if the dislike button will be gone
by the time you see this video, but if so,
just write dislike in the comments.
I go through all those.
I delete the ones I don't like.
So I'll delete that one.
Let us know if we're doing good.
Let us know if we're doing bad.
We make videos for you guys.
So we want to know which lanes to take.
Hopefully you guys enjoy this stuff.
We enjoy making it for you.
Thank you guys so much for watching until next week.
Bye for now.