Siemens VDO Supplies Mechatronics for the Variable Valve Lift Control

                  Variable control offers practical solution


    FRANKFURT, Germany, Sept. 14 Employing advanced
mechatronics for Variable Valve Lift Control (VLC) from Siemens VDO
Automotive, it is now possible -- for the first time -- to eliminate the
throttle valve for load control on a high-volume production gasoline engine.
Use of the VLC is rewarded with up to 10 percent reduction in fuel
consumption.

    The Siemens VDO VLC improves the efficiency of a gasoline engine by re-
capturing the proportion of the energy lost due to the necessary gas exchange
work of the conventional throttle valve, particularly in the engine's lower
load range, when the throttle valve is almost closed.  The Variable Valve Lift
Control method allows the gas exchange to be directly controlled by the intake
valves.  Through VLC, the intake valves close at exactly the moment the
necessary mixture is in the combustion chamber.

    A complex mechatronic system is employed in order to infinitely vary the
valve lift.  First, the engine controller calculates how much fuel/air mixture
is needed in the cylinder from the accelerator pedal position.  Then the motor
management system determines the appropriate valve lift.  This demand is
transmitted across the CAN bus to the VLC controller which, in turn, controls
an electric servomotor.  This motor adjusts the valve-actuating lever
utilizing an eccentric shaft to vary valve lift between 0 and approximately 10
millimeters.  Siemens VDO has developed three critical components in this
system -- the VLC controller, servomotor and inductive sensor, which monitors
the position of the eccentric shaft.

    The DC brush servomotor is the actual conduit between the electronics and
the mechanics.  Using a worm gear, it can adjust the valve lift from one
extreme position to the other within 0.3 seconds.

    The electronic controller is the brain of the VLC.  In order to ensure the
extremely high performance dynamics of the VLC, the electric motor requires
very high currents of up to 60 amps.  Siemens VDO engineers have taken design
and functional measures to take into account the resulting heat which could be
detrimental to electronic control.

    The eccentric shaft sensor continually communicates its position to the
controller.  In this fashion, it employs the magneto-resistive principle
conductor through which electricity flows and changes its resistance,
depending on the orientation of a magnetic field.  It is therefore unaffected
by changes in the strength of the magnetic field which can be caused by the
effects of temperature, service life or by electromagnetic interference
fields.  The changing voltage in the conductor is used to measure the shaft
angle.

    With the critical technology and system knowledge for the Variable Lift
Control (VLC), Siemens VDO is providing automobile manufacturers with a system
which, in conjunction with a variable camshaft adjustment, allows a
significant reduction in fuel consumption.  With the first customer
application in production this summer, the fuel consumption, based on the
European standard MVEG (93/116/EC), was reduced by 10 percent.  Independent of
fuel grade, the VLC system and its fuel saving benefits can be employed
successfully worldwide.

    Siemens VDO Automotive is one of the world's leading suppliers of
electronics, electrical and mechatronic technologies to the automotive
industry.

    As a development partner in the automotive industry, the company
manufactures products for powertrain, engine control electronics and fuel
injection technology which improve engine performance and reduce emissions.
The company is a market leader in information and car communication systems
with instrumentation, audio and navigation systems, telematics and multimedia
applications, through to complete cockpits.  Siemens VDO Automotive products
for chassis and carbody contribute to greater vehicle safety and security.
These products include ABS and fuel tank systems and access control systems.
A separate Trading/After Market division markets products for retrofitting in
cars and commercial vehicles.  The company was created in April 2001 as a
result of the merger between Siemens Automotive and Mannesmann VDO.

    The company's parent organization, Siemens AG, is headquartered in Berlin
and Munich and is a leading global electronics and engineering company,
employing over 447,000 people in 193 countries, with worldwide sales in excess
of $74 billion in fiscal 2000 (10/1/99 - 9/30/00).  The United States is
Siemens' largest market, where it employs over 73,000 and recorded sales of
more than $17 billion in fiscal 2000.