B2 High-Intermediate US 134 Folder Collection
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Hello everyone and welcome.
In this video we're going to be talking about
Infiniti's new VC-T engine.
Variable Compression Turbocharged Engine
Now, I personally think they should have
called it Variable Compression Ratio
and made VCRs great again
but that's besides the point and not my decision to make.
So the reason why this engine has gotten so much media hype lately
is because what it's doing is trying
to remove compromise from engines.
So traditionally you can have an engine that's really
powerful but it won't be very efficient,
or you can have an engine that's very efficient but it won't be very powerful.
So what Infiniti's trying to do here
is allow you to choose between both of those options
with the same engine.
You're not going to have both at the same time
but you can choose to run it efficiently
or you can choose to run it with a lot of power
depending on where that foot is on that gas pedal.
So the way they do this is
by incorporating this variable compression ratio.
It can be as low as 8:1
with lots of boost for high power
or it can be as high as 14:1 for a very efficiency operating condition
So how does this system work?
How does it do this?
Well it looks like this complex mess
which it kind of is but we're going to break this down,
simply so that we can understand what's going on.
So the way I want to do this is
look at this in two different sections.
This top section here
which is just going to be like a normal engine
and then this lower section here
which is going to be used to adjust the compression ratio.
So for now, let's just ignore everything below this
and look at what we've got going on up top.
So here we have our piston, the connecting rod, the cylinder, everything like usual.
The difference here is this crankshaft,
so you can see there's this rectangular piece called the multilink.
and that's going to be linking up these two sections.
And so your crankshaft, is going to be right here,
the center of rotation, right there.
So, to give you an understanding of what this looks like
here we have a crankshaft,
and so this right here
is this right here
and then the center, this axis which it rotates about
is of course right there, so looking at this
this crankshaft right here how this will be oriented
would be just like that
with the center right here and this will rotate around
This piston will come down and up and down and up
And rotate this section
And now important thing you need to understand is that this multi link right here this rectangular piece
maintains this orientation as it goes
around the crankshaft it doesn't rotate

it maintains that orientation and so
that's what we're gonna be using

to change the compression ratio
is changing the angle of this

rectangular piece right here so you can
see if you were to tilt it up that would

cause this piston to move up increasing
the compression ratio and if you were to

tilt it down that would decrease the
compression ratio pulling the piston

down so what we're looking at right here
is top dead center the crankshaft

oriented like that so you've got the top
of it right here and then the center of

it right there and it's about to rotate
down like that. So how this works on the

compression ratio adjustment system
basically all you need to know about

this side of the system the most
important piece is that what you're

trying to do is to move this lower link
up and down because as you move this

lower link up and down you change the
orientation of this rectangular piece

this multi link and so if you were to
pull it down you can see it increase the

compression ratio because it pivots
about this point pushes the piston up

and if you were to push it up you would
pull the piston down decreasing the

compression ratio at top dead center
Okay great so how does it do this?

Well, the magic of it really comes down to
this central shaft right here but

basically we have a harmonic drive right
here you can just think of this as a

device which rotates clockwise or
counterclockwise and then you have this

actuator arm which rotates this central
shaft. So the central shaft rotates about

this pivot point right here so you can
see if this central shaft were to rotate

downward if it were to rotate down that
direction it's going to pull this lower

link down and by pulling that lower link
down it's pushing the piston up

increasing the compression ratio. I f it
were to rotate upward if this piece were

to rotate up like that it's going to
push up on here and then that's going to

pull this down and that's going to
decrease your compression ratio so it's

all dependent on which way you turn this
actuator arm it's linked up and it's

going to cause this to pivot about this
point right here so you can see

currently this is the state it's in if
you were to rotate it using this linkage

you could rotate it down and you would
increase your compression ratio to 14:1

or you could turn it all the way up
and that would push this up pivot this

down and that would decrease your
compression ratio down to 8:1 so you

know once you kind of see all of this
work together it's really not that

complicated but it is kind of a mess
looking at all of it together

and so the important thing to
just kind of see is that it can rotate

this rectangular piece rotates around
the crankshaft about this point right

here and then these two pieces right
here these two links keep this

rectangular piece in that orientation as
it goes around and you can change that

by changing the height of this lower
link using that central shaft great

that's all clear right? And so you know
why do you want to do this? Well as I

mentioned you kind of remove that
compromise so you can use a low

compression ratio you can put in tons of
boost and so why do you need a low

compression ratio well you want to
prevent knock and so you know you can start

to get into some tricky scenarios if you
have high compression ratio and high

boost so to make it safe reliable you
decrease the compression ratio and then

you eliminate, you know, you reduce your
chances of knock and you have a safer-running,

more powerful engine well then
you can pump it up to that 14:1

to get that really high efficiency not
only does 14:1 have a higher

thermal efficiency but they've used this
in combination with the Atkinson cycle

so they're using variable valve timing
to leave those intake valves open for a

short duration during that compression
stroke and that improves the efficiency

I have a whole nother video explaining
how that Atkinson cycle works if you're

interested but basically what they're
doing is giving you really good

efficiency in one operating condition
and lots of power in the other operating condition

So, is it going to be the most
efficient two-liter engine out there?

Well no, of course not. And is it going to be the most powerful 2-liter engine out there?
No. but what it's doing is its
allowing you to choose between both of

those so if you're cruising down the
highway you can get great fuel economy

and then if you're ripping through you
know a canyon you can actually have some

fun it'll decrease the compression ratio
load it up with boost and you've got

all kinds of power so it is a very cool
option to give you efficiency when you

want it and power when you don't so
thank you guys for watching and if you

have any questions or comments feel free
to leave them below

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Infiniti's Amazing New Engine - Variable Compression & Turbocharged

134 Folder Collection
kinhuabin published on September 2, 2017
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