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For the trade press

More performance with less consumption Series production of piezo direct gasoline injection about to begin

Vienna, April 28, 2006

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

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piezo direct gasoline injection

Piezo technology from Siemens VDO increases the performance of gasoline direct injection engines and enables fuel savings of up to 20 percent