More performance with less consumption
Series production of piezo direct gasoline injection about to begin
Piezo
technology from Siemens VDO increases the performance of gasoline
direct injection engines and enables fuel savings of up to 20 percent.
Siemens VDO's piezo direct injection system, seen in the BMW Twin Turbo
engine at the 2006 Geneva show, will go into series production this
fall. The introduction of an engine suitable for stratified charge
operation in a volume model is planned for 2007.
Thanks
to piezo technology, direct injection engines will be even more
economical and cleaner in the future. The new piezo injectors offer
greater speed, precision, and control possibilities, compared to
solenoid gasoline direct injection technology. In comparison to a
manifold fuel injection piezo direct gasoline injection and
stratified-charge operation allow fuel savings of up to 20 percent,
while also improving raw emission values. These improvements are
possible because the precise control and rapid switching of Siemens
VDO's piezo actuators are used in conjunction with the newly developed
high-pressure pump that delivers the fuel to the rail at a pressure of
up to 200 bar.
The
new piezo injectors allow the use of a stratified charge at higher
driving speeds and engine loads. So the economical stratified charge
operation that can be substantially expanded on engines of larger
capacity, which Siemens VDO will implement in a future generation of
BMW engines.
How the technology works
The
stable spray characteristics of the piezo injectors and the fine
atomization of the fuel, in combination with the ability for multiple
injections, are ideally suited to spray-guided combustion at partial
load. During the combustion process, gasoline is directly injected into
the combustion chamber near peak pressure to better utilize the
gasoline, resulting in a combustible mixture only in the immediate area
of the spark plug. Because this mixture is formed in the upper part of
the combustion chamber, and there is no mass of combustible mixture
below, it is now a stratified charge. Spray-guided combustion, which is
the most-efficient form of stratified charge, is only possible with the
performance features of piezo technology because a precise, constant
injection must be directed to the immediate spark plug area.
A question of control
Optimized
control, based on modular Engine Managment System architecture (EMS 2),
can utilize the technical potential of the new injectors flexibility,
especially in regards to their precision. Siemens VDO has used its
extensive electronics and mechatronics knowledge and diesel piezo
technology experience to design the control of the gasoline piezo
injectors as flexibly as possible. For example, a great deal of
optimization effort went into driver software development in the
control unit. Intelligent control of the current profile ensures the
piezo element's electrical charging and discharging takes place in a
very rapid and controlled fashion allowing the injector needles to
gently close. The needle stroke can be set individually by cylinder. In
addition, the final stage allows the piezo actuator's electrical data
to be captured and analyzed, enabling a regulated control of the piezo
element and its function to be monitored thoughout its entire lifetime.
Injection as the key to greater efficency
With
its ability to be controlled flexibly, piezo technology puts additional
possibilities in the engine developer’s hands in order to influence the
available torque, fuel consumption and combustion, as well as the
engine’s raw emissions and exhaust gas aftertreatment. In this way,
piezo injectors can inject up to four different-sized portions of fuel
into the combustion chamber during a single cycle and the injections
can take place more flexibly than with solenoid technology. This
technology can be used in a stratified charge operation to increase the
area of the combustible mixture with two injection pulses. In addition,
it makes it possible to favorably influence the exhaust gas
aftertreatment and the heating of the catalytic converter by late
injection of an additional portion of fuel. The piezo injectors, which
open outwards, support a broad span between the minimum and maximum
injection amounts enabling engines with high cubic capacity to achieve
greater economy at partial load, while ensuring optimum cylinder
charging at full load.
Showing their strength – direct injection with turbochargers
For
the first time in Geneva, Siemens VDO’s piezo direct injection was
introduced as “high-precision injection” in the new BMW twin turbo
engine. The new BMW 3-liter twin turbo engine is exceptionally
economical for its high performance. The powerful engine illustrates
the contribution that piezo technology, in combination with an
intelligent charging concept, can deliver with an increase in torque on
homogenously charged engines. Its efficiency counteracts the tendency
of turbocharged engines towards higher consumption. Driving fun and
fuel economy are brought closer for engines with high cubic capacity.
Pioneer of Piezo
Siemens
VDO is the pioneer of piezo injection technology: production of the
first generation of piezo injectors for diesel engines began back in
2000. Since then, the company has continued to drive development of
piezo actuation forward. The transfer from diesel to gasoline engines
is an additional milestone in the development of engines with
ever-greater thermodynamic efficiency.
Siemens
VDO Automotive is a leading international automotive electronics and
mechatronic supplier. The group is part of Siemens AG and generated
sales of EUR 9.6 billion in the 2005 business year (30.9.).
Reference Number: SV 2006.04.002 e