Common-rail injection: very fast and very clean
Common-rail diesel: In 2012, at least four of every five diesel vehicles sold worldwide were equipped with a common-rail system. Bosch is the market leader for this technology: in 2012, more than 8 million systems were delivered, and in 2015 this number will reach 12 million – a 50 percent increase.
Piezo injectors – high-pressure pioneers: The CRS3-25 common-rail system features the first piezo injector from Bosch for passenger cars to operate at 2 500 bar. With their increased injection pressure, these new Bosch piezo models are on the technological cutting edge. By optimizing injection, fuel is more finely atomized and can be better burned. Moreover, advanced piezo injectors enable multiple injection comprising up to ten cycles. This is important, as it will make complying with future emissions limits and further increasing engine performance possible.
Solenoid valve injectors: Along with piezo systems, solenoid valve injectors are also continuously being optimized. One example of this is the new Bosch CRI2-20, which provides an injection pressure of 2 000 bar. All Bosch solenoid valve injectors have been designed according to a modular principle, which allows automakers to use different model generations in the same basic engine.
Continuous improvement: A further increase in pressure is also possible for solenoid valve injectors. Pressure-balanced valves make this possible, as a high-pressure accumulator integrated into the injector prevents pressure fluctuations in the system. Fuel can be more efficiently injected this way, resulting in lower emissions and a quieter system. Just like piezo injectors, solenoid valve injectors make multiple injection possible. This helps to reduce fuel consumption, thereby cutting the levels of CO2, pollutants, and noise emitted by the engine.
Background information: piezo injectors and emissions standards
How piezo injectors work: The piezoelectric effect enables the transformation of mechanical load into an electrical signal and vice versa. When an electrical current is applied to piezoelectric ceramic, its length instantly changes shape. This change in length can be used to generate mechanical force. A piezo injector uses this effect to activate an injection valve’s opening and closing mechanism. In 2005, Bosch and Siemens VDO were jointly awarded the German Future Prize for bringing piezo technology into series production.
Milestones: Series production of common-rail systems in passenger
cars began in 1997. The system was first installed in the Mercedes-Benz C 220 CDI and the Alfa Romeo 156 JTD. At that time, it delivered injection pressure of up to 1 350 bar. Beyond that, diesel technology has also celebrated considerable success in motor racing. Since 2006, diesels have won every 24-hour race at Le Mans. All the winning cars have had specially-developed Bosch racing technology on board.
Emissions legislation: Bosch injection systems play an important role in ensuring that diesel vehicles worldwide are able to comply with current and future emissions standards. By further increasing pressure and improving injection, automakers will be able to perfectly synchronize engine operation with exhaust-gas treatment.
Fuel quality: One challenge for injection systems is the inconsistent quality of fuel worldwide. For example, the lubricant properties of diesel often vary considerably between regions. With this in mind, Bosch has developed its common-rail injectors to be fundamentally suitable for worldwide use.
