Contacts: Marlene Goldsmith (248) 372-8222 marlene_goldsmith@denso-diam.com Julie Kerr (248) 372-8260 julie_kerr@denso-diam.com DENSO's 1,800-Bar Diesel Common Rail System with Piezo Injectors Diesel-powered vehicles involve excellent fuel economy and power, and their popularity is especially high in Europe _ about 35 percent of vehicles on European roads have diesel engines. In North America, diesel-powered vehicles are not as popular as in Europe, with the majority of diesel-powered vehicles being trucks and heavy-duty construction and agriculture applications. In the SUV and large pick-up car category, there is growing demand. Key challenges with diesel engines are how to reduce concentrations of harmful substances in emission, such as nitrogen oxides (NOx) and particulate matter (PM); and the strict and varied emission regulations around the world. DENSO has been developing various diesel engine management systems and components that reduce these harmful substances while improving performance. DENSO launched the world's first innovative common rail system in late 1995, and it continues to develop and improve its state-of-the-art common rail system. In 2002, DENSO developed a 1,800-bar common rail system that achieved a high injection pressure _ 1,800 bar, the highest in the world _ and comfortably cleared EURO 4 emission regulations. In Europe, this system was installed in the MPV vehicle, manufactured by Mazda Motor Corporation in June 2002. Also, the Mazda 6, launched in September 2002, is equipped with this system. Recently, DENSO began producing the world's first 1,800-bar diesel common rail system with piezo injectors, which it jointly developed with Toyota Motor Corporation. The new system uses highly responsive piezo injectors to attain a shorter injection duration and realize a finer fuel atomization spray, resulting in improved performance. As a result, the system helps generate higher engine power and reduces NOx and PM. Compared to a solenoid injector, this piezo injector with its DENSO-developed highly reliable piezo element, reduces the minimum injection interval from 0.4 milliseconds to 0.1 millisecond, the shortest interval in the world. - more - System Structure DENSO's 1,800-bar common rail system is composed of: * Supply pump * Common rail with a high-pressure sensor * Piezo or solenoid injectors * A high-speed, 32-bit engine electronic control unit (ECU) integrated with an electronic injector driver unit (EDU). In the common rail system, fuel is pressurized by a supply pump, transferred to a common rail through pipes, accumulated in the rail, and then injected into combustion chambers by the piezo or solenoid injectors. Accumulating fuel at the common rail allows not only pressuring fuel at a higher pressure, but also controlling fuel pressure and injection timing independently from the engine speed. The fuel pressure in the common rail is detected by the high-pressure sensor, and controlled by adjusting an electromagnetic valve of the supply pump to match an optimum value preset in accordance with engine speed and load. This enables high-pressure injection even at a low engine speed and allows fuel to be atomized sufficiently at any engine speed range, thereby reducing the amount of PM in emission. Features and Advantages * DENSO's common rail system can inject fuel at up to 1,800 bar, significantly reducing the concentration of PM in emission. * The high fuel injection pressure is generated by the supply pump, which is the lightest in the world for common rail systems. * DENSO's new piezo injectors can inject fuel at an interval of 0.1 millisecond with a required small quantity - only one cubic millimeter per one injection. The injectors allow the system to perform five injections during each combustion stroke. The five times multiple injections, having predetermined fuel quantities, reduce PM and NOx in emission, and realize quietness equivalent to gasoline-powered engines. Injection quantity deviation requirements from car manufacturers are increasingly severe, and DENSO is striving to improve machining technology with micron-machining techniques to meet these requirements. Further, DENSO developed a software compensation method for the new common rail system, which compensates injection quantity deviations among the injectors. Specifically, by adopting a two-dimensional code, each injector has a code that contains its own deviation. The engine ECU then reads deviations of the injectors during assembly and compensates for them. In addition, to keep the precise injection quantity of each injector, DENSO developed software that allows only one cubic millimeter per one injection while maintaining a variation of 0.5 millimeters or less during its operation. As a result, the system can keep performing injections with required small fuel quantities, at high accuracy during its operation. - more - Outlook of Common Rail System DENSO will continue to further develop common rail systems to meet emission regulations, which will be stricter worldwide, provide cleaner emissions, and quieter and more powerful diesel engines. ###