After nearly a decade of work, Siemens Automotive says it will be the first supplier to begin volume production of piezohydraulic injectors, opening the door to the second generation of common-rail diesel injection for passenger cars.
A Western European customer will be the first to receive the new high-pressure injection system, by the end of next year, followed soon after by a second major vehicle manufacturer. Siemens expects common-rail to accelerate the penetration of diesel engines in the European passenger car market and potentially the U.S. car market, which has been less receptive to diesel.
The benefits are numerous: improved fuel consumption, increased horsepower and reduced emissions and noise. Fuel can be metered more accurately and the start of injection can be determined with greater precision, the company says.
A high-pressure pump generates system pressure of 21,750 psi (1,500 bar), compared to 44 psi (3 bar) for solenoid-activated port injectors used today for gasoline engines. The system, employing a piezoceramic actuator, responds to each voltage pulse within 0.1 milliseconds, which is more than four times faster than solenoid injectors.
In addition to the injectors and pump, the Siemens system comprises actuators with corresponding sensors, engine control and the fuel rail.
Siemens displayed the system at the recent Frankfurt International Motor Show. The company has invested $80 million in high-pressure diesel injection and will produce the system at a new plant in Limbach-Oberfrohnanear Chemnitz in the former Eastern Germany.The plant currently has 300 employ ees and a production capacity for 2 million units per year. Also, in 2001, the plant will begin producing diesel injection valve nozzles for light- and medium-duty commercial vehicles in the U.S. as a part of Siemens' new joint venture with Navistar International Corp.
While the product is new, Siemens' involvement in fuel injection is anything but. The German-based company already makes 35 million injectors a year for gasoline engines. Ultimately, the company sees potential to use the same piezohydraulic injectors for gasoline engines as well.
Meanwhile, competitor Robert Bosch GmbH says it will introduce its next-generation diesel common-rail system in 2002. The Bosch system, also employing piezo actuators, generates injection pressure of up to 23,200 psi (1,600 bar).
With the benefits to performance and emissions, Bosch says common-rail ensures expansion of the diesel market. Western Europe already is seeing such growth. In 1998, diesels made up 25% of the passenger car market in the region, up from 22%, an increase of about 450,000 vehicles.
