hello everyone and welcome behind me is
the 2016 bmw x1 and in this video we're
going to be talking about valvetronic
bmw's infinitely variable valve control
system now bmw engines like this 2-liter
turbocharged engine in the x1 operate a
bit differently than traditional
gasoline engines in most gasoline cars
when you press the gas pedal you're
changing how much the throttle valve
opens a butterfly valve regulating the
amount of air that enters the engine in
bmw engines with valvetronic however a
throttle valve is not necessary and when
you press the gas pedal you're altering
how much the intake valves open there is
indeed a throttle valve in these engines
but it is simply used as a failsafe
under normal operating conditions the
valve will always remain fully open
there is a major efficiency benefit of
regulating airflow this way as it
reduces the pumping losses of the engine
particularly at low load operations or
any time you're not flooring it with
throttle bodies you have close to
atmospheric pressure on the filter side
and a vacuum on the intake manifold side
with valvetronic you'll have near
atmospheric pressure directly outside
the intake valves and thus the engine
does not have as much resistance to
pulling in air making it more efficient
bmw claims this valve train design
improves fuel consumption by at least 10
percent under practical driving
conditions so how does the system work
well in order to understand we're going
to look at it with the intake valve
fully closed and then look at it with
the intake valve fully open and so what
we have here is the valve train which is
located above the cylinder here we have
the intake valve of course and the
intake manifold right here and so what's
happening is we have an electric motor
here up top and so it's attached to a
worm gear which can rotate this
eccentric shaft which you can see has
this profile here which will follow
along on this intermediate shaft now the
intermediate shaft is acted upon by the
camshaft so it has a spring which is
forcing it into that camshaft and then
it will of course with this roller
follow the pattern of the camshaft
so as you can see the cam is at its
highest point on its lobe right here so
that means you know in any traditional
engine the intake valve should be fully
open but as you can see it's still
closed and so the reason for that is
because on this intermediate arm here in
the middle it has this long flat portion
so as long as this rocker arm is on this
flat portion here it's not going to be
acting on the intake valve at all
and so that rocker arm is what's
actually going to be opening and closing
that intake valve and so what happens is
when you open it you're going to start
to rotate this gear this way and as you
can see that profile will push this
intermediate arm closer to this camshaft
and so as a result it's going to rotate
it and as it rotates it that means this
bottom portion here where it starts to
curve is going to start to push up
against this roller
and so here where we have it fully open
you can see it's rotated all the way and
now it's rotated so now this bottom
portion is right up against that roller
that means this part has to be forced
down so it's pivoting here and it's
going to push that down and as it pushes
it down it opens up that valve and so
because of this profile right here you
have an infinitely variable system
between zero millimeters with it fully
closed and 9.7 millimeters with it fully
opened and this was introduced by bmw
back in 2001 and even back then they
said that they could go from fully
closed to fully open in just 0.3 seconds
so they've probably improved that time
since then as technology has improved
but you know going back to the very
basics this is how that worked now there
are additional benefits to this system
as well with throttle bodies once you
floor it you have to wait for the air to
travel from the throttle body to the
intake valve by using valves to regulate
airflow and already having nearly
atmospheric pressure right outside the
cylinder the intake is immediate and
thus response is improved another
benefit at low load operations the
valves will only open about 0.5
millimeters to about 2 millimeters and
this cross-sectional area means that the
air fuel mixture will move rapidly
improving fuel atomization this also
helps with cold starts now you might be
wondering how does the system allow for
vacuum assisted brakes if there's not a
sufficient vacuum in the intake manifold
this is handled by a vacuum pump located
at the end of the outlet camshaft thank
you all for watching if you have any
questions or comments feel free to leave
those below