|Direct injection concepts. Source: Orbital|
Declaring that a few per cent less fuel consumption throughout an entire model range gives the public and society in general more than a significant improvement of fuel economy on just one niche model, BMW has stated that it will implement spray-guided direct injection on all its gasoline models in the future, as well as regenerative braking and stop/start functionality.
These systems constitute what BMW introduced at Frankfurt IAA as its Efficient Dynamics Technology package.
High-Precision Injection (HPI) is a lean spray-guided gasoline direct-injection technology that BMW projects will increase fuel efficiency by up to 10% in the Euro test cycle and between 5%–15% in real world driving.
A gasoline direct injection (GDI) engine sprays the fuel directly into the combustion chamber of each cylinder (as opposed to a port fuel injection (PFI) or carburetor engine) and delivers significantly increased performance and decreased fuel consumption and emissions.
First-generation GDI systems are wall-guided—the spray hits the wall, and the formation of the fuel-air cloud depends mainly on the charge movements. A spray-guided technique uses the injection procedure itself and not the charge movement to ensure that a combustible mixture is brought to the sparkplug at exactly the right time, regardless of pressure and temperature conditions.
Systems providers such as Bosch (long-time BMW partner), Delphi, Siemens and Orbital are all working on their spray-guided direct injection technologies, with other automakers, such as Audi and DaimlerChrysler in partnership.
In the BMW HPI system, the injection valve is configured as a piezo-injector and positioned in the middle between the valves and the spark plug at the center of the combustion chamber. Injection is at 200 bar—an increase over current systems.
In the BMW application, the engine is able to run on a lean mixture all the way from idle speed to high revs. This delivers the enhanced fuel economy.
BMW High Precision Injection will first be launched in the European markets.
BMW will also implement regenerative braking via an intelligent alternator control concept that will recharge the battery when braking or coasting. Relieved of the workload to drive the alternator, the engine can apply more of its power to motion.
The third component is Auto Start/Stop. This system will automatically switch off the engine in as soon as the car comes to a standstill, with restart triggered by pressing down on the clutch or the gas pedal. Similar to the intelligent alternator control for regaining brake energy, the Automatic Engine Start/Stop System is based in principle on conventional components.
The main difference is that software now serves to link the various sensors, the starter and the alternator control with one another.
BMW did not provide a timeline for implementation.