hello everyone and welcome this video
we're going to be talking about variable
valve lift and variable valve timing and
to help explain this we have Charles mr.
Hubbell Mocambo who brought some VW
parts some outtie parts to help swing
this so what is in front of me right now
so these are camshafts and a cam bridge
out of an own Einaudi a four this is
almost the exact same setup that you'll
find in the 15 and up mark 7 GT is we
have our exhaust cam with variable valve
lift and we have our intake cam with
variable valve timing sweet so yeah as
you mentioned we've got our intake right
here intake cam exhaust cam and the
basics we're going to start here with
the variable valve lift which is on the
exhaust side and basically what you're
doing you have two different cam
profiles so you have this higher cam
profile and then you have a little bit
lower of a cam profile and you have an
individual system for each cylinder so
you can move this back and forth it's on
a spline so you can move that and each
individual cylinder has its own control
and so Charles can you kind of explain
the details of how this system actually
moves back and forth to change that cam
profile right so like Jason said these
are essentially sleeves that are spline
to the camshaft we have two solenoids
that will control this sleeve one
solenoid will pull it one way the other
solenoid will pull it the other way when
the solenoid is activated the pintle
will come down and ride in this channel
and it'll actually slide that sleeve
over to change the profile of the
camshaft that the rocker is riding on so
if we are riding on our high lift this
solenoid will activate it'll pull it
over and that will allow us to ride on
our low lift when we're ready to go back
to high lift this solenoid will activate
pulling in the other way and allowing us
to ride on the high lift profile of our
cam and of course this will have two
valves per cylinder so you'll have a
rocker here as well as a rocker here
this is a pretty narrow rocker to be
able to ride on both of those profiles
and so kind of interesting thing about
this is that it's on the exhaust side
and not intake side you have one
and profile here on the intake side on
the exhaust the reason for this this is
a turbocharged engine and so you've got
pressure pushing in air it's fairly easy
to get that intake charge but it's then
difficult to get all that air all that
exhaust out and so once you get into the
higher rpm at higher loads and you're
burning all this air and fuel you want
to open these exhaust valves a little
bit more so it's easier to get that air
out and you can create more power less
losses more power so that's kind of the
beauty of this VBL system right this
also improve throttle response a little
bit and makes for a pretty fun car yeah
it's pretty sweet
now just because this engine doesn't
have this on the intake side doesn't
mean you couldn't do that you could have
two different cam profiles and use a
very similar system on the intake side
and you'd get that benefit of getting in
more air once you're at higher rpm
higher loads so you can make more power
and you can also change the duration
with the two cam lobes so you were
saying you notice you know these are
it's not just lift we're not just great
opening the valve more we're also
opening it sooner and we're actually
closing it a little bit before we would
on the low lift okay but not very much
so the duration is actually longer as
well okay so much more time and lift for
all that air to get out for efficiency
and you know not not losing all that
power getting too much pressure going
out your exhaust so very cool yeah and
that's all ECM controlled so the engine
computer is going to do that based on
the scenario the vehicle is in it in a
lot of ways knows better than most of us
on what it wants from the engine
definitely me definitely better than me
yeah I just poked at computer in try
beep yeah so moving along to the intake
side this as you can see just a single
cam profile and what we have here is our
variable valve timing and so if I hold
this stationary and you can see the
chain won't move and we can advance it
or pull timing back and the
timing so as you can see on intake there
is only one cam profile and so all we're
doing is let's say you know you have
your cam profile open close you're just
shifting when it opens and closes back
and forth and that's all you're doing
the cam
files remaining exactly the same so
we're going to talk about why you would
want to shift when the intake valve
opens and closes but first let's take a
look inside and see how this works so
the variable valve timing is all based
on oil pressure when the profile wants
to change one way the well will fill up
here and shift this way if it needs to
shift the other way there's another port
and it will shift this way and then when
it wants to bleed down the pressure
there's actually a release or relief
hole right down here at the bottom then
this oil will fall down the timing chain
side and it'll reset back to zero cool
so all you're doing I mean you've got
this little you know complicated chamber
that's sending out oil and all you're
doing is filling either one side with
oil or the other side well they both
have a port and then you can drain it
out the back there that's it it's all
controlled there's actually on the
timing cover which goes in front of this
there's a solenoid that goes there this
is a spool valve like you said that has
different chambers and ways to pass oil
through this there's actually another
part to it right here that you guys
don't need to know about so as you know
you know probably worth mentioning that
when you're thinking about this this
gear is remaining stationary I mean
obviously it's spinning right but the
cam is rotating in relation to it the
actual shaft is rotating not the cam
gear so this is more what it would look
like if you could get in there and see
it in action so now we're going to talk
about why you want to do this why you
want to change the valve timing and so
we're going to start with the example of
a late intake valve closing so we're
closing our intake valve later than
usual so why would you do this well when
you do that that means your cylinder is
going to be starting to go back up to
compress that air and your intake valve
is still going to be open so you're
going to push some of that air fuel
mixture back out into the intake
manifold now there are some pumping
losses associated with that where you're
going to reduce those pumping losses
because you're now charging your intake
manifold but really the main thing
you're doing here is you're controlling
how much air and fuel you have in that
combustion chamber and in doing so how
much combustion you're going to have how
much you know power you're going to make
and so you can reduce the temperature of
that cylinder by using less air and fuel
and so by reducing that temperature
you're going to have
NOx emissions so the common theme of all
these different scenarios of kind of
choosing do you open the intake valve
earlier late or the exhaust valve you
you know you closed it late or early the
common theme with all of these is going
to have to relate to emissions right
that's how that's how we look at it is
and it's mostly done by controlling
temperature and therefore controlling
Analects emissions
so Jason why would you close the intake
valve early well Charles let me tell you
why the intake valve early this really
has to do with situations where you're
basically just idling or it's super low
load so what's happening when you're
just sitting there idling is you really
don't need much air fuel to keep this
engine idling and so you'll close that
intake valve early and effectively what
you're doing is reducing the amount of
pumping losses you have because that
piston is trying to pull in air and fuel
you get enough you have enough for what
you need to just idle the engine and
then you close that intake valve early
it continues to go down and you're no
longer pulling on that vacuum and then
you would have more pumping losses so
from an efficiency standpoint it's just
a smart thing to do when you're sitting
there idling to close intake valves
early so Jason why would you open the
intake valve early well Charles let me
tell you why you open the intake valve
early so this means you're on your
exhaust stroke so you're pushing out
that exhaust gas and now you're opening
that intake valve so what you're doing
is you're pushing some of that inert gas
that exhaust back into your intake
manifold and this is kind of similar to
the principle of like EGR why you would
use an EGR system so that inert gas is
in there that comes in you're
controlling the temperature of
combustion chamber once again to reduce
NOx emission it's all about the NO x all
about the NO x yep
so Jason why'd you change the time and
you closed your exhaust valve well
Charles let me tell you about closing
exhaust valve so the important thing
here once again comes back to NOx
emissions so if you close the exhaust
valve early what you're doing is
trapping some of that exhaust that
ignore gas in the combustion chamber and
then when your intake stroke occurs you
still have some of that inert gas in
there and thus you know you're going to
have lower combustion temperatures and
lower NOx emissions the other side if
you want to close it later of course you
can get all of that exhaust
out of there so that you can fill it
completely with fresh air and fuel and
get more power now obviously you don't
want to open the exhaust valve early
that's during your combustion stroke as
you can just be sending power out your
exhaust and shooting flames which would
be cool but you wouldn't it appeals it
is the peak of inefficiency and that's
where like combining these two together
really get interesting with lift and
timing because you can control way down
way way down and what you're trying to
get under your engine super down out of
your engine well thank you all for
watching and Charles thank you once
again for hosting me in your lovely
garage absolutely supplying these great
parts it's always a pleasure and if
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