The BMW VANOS system and Honda VTEC system both allow for variable valve timing to optimize engine performance at different rpm levels. VANOS continuously adjusts the timing of the intake and exhaust valves by changing the position of the camshaft relative to the sprocket and timing chain. VTEC uses a third cam lobe that engages at high rpm to increase valve lift and duration. Below a certain rpm, only the outer cam lobes operate while the center lobe idles. Then oil pressure engages the center lobe for more airflow at higher speeds. Both systems aim to improve torque at lower rpm and power at higher rpm through dynamic valve timing tailored to the engine's operating conditions.

1. distribution systems
Introduction
This paper intends to explain the operation of the variable
distribution of BMW (VANOS).
To understand this article you must first have an inkling of operating
a multi-valve engine (with dual overhead camshafts) of the basic
components and how they interrelate. I refer primarily to the
crankshaft, connecting rods, pistons, chain / timing belts, camshafts
and valves. Without such prior knowledge will be difficult to understand
what you explain.
The idea
The set of pieces of the "distribution" is responsible for moving the
valves in sync with the crank to open and close at the right time.In this
variable valve timing engines without synchronism is fixed, by that I
mean that the valves always open and close at the moment with
respect to the position of the piston, where the piston reaches a certain
position, the valve opens, always happens the other, the valve closes,
no matter what rpm take the engine, always occurs at the same time.
The point is that for each r.p.m. Engine is an optimal time of opening
/ closing of valves, an optimal standard, an optimum opening
time ... This means that if the distribution is fixed it only optimizes the
synchronized pistons and valves for a rpm point, and out of there we
have a performance could be improved.
The definition of serious VANOS, variable valve timing system for
BMW which is responsible for changing the times of opening / closing
the valves with respect to the position of the piston according to
rpm engine. What it does is sync continuously optimize for better
performance at all times. Its operation is based on the camshaft and
the distribution chain are not linked directly, but there is an
intermediate piece which is responsible for changing the relative
position of the camshaft with respect to the sprocket on the chain
passes .
Honda VTEC System
Acronym for Variable Valve Timing and Lift Electronic Control
System. Honda presented in 1989 a system for varying the time of

2. distribution, in which the camshaft is not twisting. Not only regulates
the opening phase, but also time and the same section. The objective
of this measure are laws designed to measure the opening of the
valves for different speed regimes. For a number of revolutions
average, shorter opening times and a lower valve lift raise the gas
velocity and thus also the filling and the torque in this range. For a
higher speed number, the longer opening times and a larger valve lift
intensify engine breathing, which in turn has an effect on power.
The method by which this effect can be achieved, requires up to 4
valves per cylinder, 6 and 6 rocker cam lever. External cams, which
are assigned directly to the valves, carry profiles and cam soft core has
the longer delivery times and running bigger cam. At low rpm, just
outside the cams are active, while the central cam is driven, as it were
somehow empty, ie has no effect on the valve rocker lever of
power. An additional spring prevents the loss of the contact between
the cam and the rocker lever. There are some pins that can be moved
hydraulically, and that between 5000 and 6000 rpmmake a mechanical
connection between the rocker lever 3. Since that time the largest
central cam which marks the opening of the valve. Delivery pressure
required to move the circuit provides the engine lubricating oil. For the
coupling of the rocker lever works well, it is necessary that the base
circle cams are all equal, so that when the valves are closed
accommodation and the pins are aligned.
Honda has demonstrated the ability of system performance VTEC
(DOHC) having two camshafts located at the top
Summarizing the variable distribution system employed by Honda in
cars is based on third cam in each cylinder which comes into operation
at high rpm. The swing of the cam does not work at low revs, while at
speed, oil pressure moves a rod between other camshaft rockers and
central cam, leaving the whole ensemble together. At this point the
rockers are opened by the higher profile cam (the middle) and
increasing the valve lift and the moment of opening and closing. When
the engine reduces the engine speed picks up the stem and the rocker
panel is loose. The profile is now active external cam. This system is
coupled to the intake and exhaust valves in the engine with twin
overhead camshafts (DOHC) and only the intake valves of an engine
camshaft (SOHC).
Depending on the locking pins or bolts are available in the following
states of operation.
State 1: Under the 2500 rpm and the engine at low load, the three pins

3. are unlocked so that arms can rotate relative to each other.The left
over is supported by a machined ring on the camshaft, so that the
height of the corresponding valve is void, remaining closed. The
engine then will be running in either 12 valves (3 valves per
cylinder). The intermediate swing not be located not operate any
valves.
The swing to the right is driven by the cam profile smoothing,
individual valve actuation, which results in a distribution diagram of an
engine itself elastic with a high combustion efficiency.
State 2: When you have exceeded the 2500 r.p.m. or accelerate, the
bolt is inserted higher pressure and isolation, with the rocker ends are
forced together. Thus the two intake valves are driven by the milder
cam profile, so running the engine 16 valves. The engine operates in
this state from around 2500 rpm to 6000.
State 3: When the engine exceeds 6000 rpm pressure is sent to the
lower bolt, making the three rocker solidarity, which become activated
by the cam profile of greater height. This results in a higher power,
typical of a fast motor.