Delphi's Revolutionary Direct Acting Diesel Fuel Injection System
December 2008
News, Injectors
Delphi Corporation has announced that, following several years of development in cooperation with Daimler engineering teams, the new Mercedes C250 CDI will premiere Delphi's revolutionary Direct Acting Piezo injector.
The new Direct Acting Common Rail (CR) from Delphi represents a radical break-through in diesel injection technology as, for the first time, the injector needle is directly activated by the piezo stack, removing the hydraulic circuit and its associated lag and energy consumption. This change enables vehicle manufacturers to comply with future emission legislations while providing more power and uncompromised fuel economy.
"Today, Delphi surpassed a major milestone in diesel technology history," said Jose Avila, general manager of Delphi Diesel Systems. "And there is no better way to write this new chapter than to be partnered with Mercedes-Benz, the company with the industry's longest history in diesel engines."
Delphi's Direct Acting CR system uses a patented direct-acting concept in which the injector needle is set in motion directly by a piezo ceramic actuator instead of being moved via an electro-hydraulic circuit as with existing fuel injection technologies. The piezo ceramic actuator directly operates the needle valve of the injector for initial lifts, such as those obtained in pilot injections, and a motion amplifier is used to help complete the lift for large injections. This enables the injector to spray fuel into the combustion chamber faster, with much improved spray momentum and accuracy, at higher pressures (up to 2,000 bar). It also provides extremely fast opening and closing of the needle valve, independent of injection pressure. With needle velocities reaching above 3 m/s or 3 times faster than today's servo systems, the system allows seven (or more) injection events per engine cycle. Delphi's hydraulic circuit design makes best use of the characteristics of piezo ceramic actuators: high force and speed with efficient packaging.
Thanks to high-precision multiple injections of fuel, the fuel injection process can be adapted to all engine loads and speeds with greater accuracy, which has a positive impact on emissions, consumption and combustion noise. By offering the ability to control the needle opening rate electronically and independently of hydraulic constraints, the engine calibrator is able to satisfy the conflicting requirements of noise optimization and minimization of exhaust emissions without compromise.
At idle, the Direct Acting injector concept makes no perceptible noise above the engine itself, which is a remarkable achievement when compared with today's servo piezo injection systems.
Moreover, thanks to the innovative actuation concept, the injector's radically new operating principle is also completely leak free. So, no high-pressure fuel is wasted into a return flow back to the tank, saving up to one kilowatt of lost energy used by today's servo systems and removing the requirement of expensive fuel coolers even at a rail pressure of 2,000 bar. Overall benefits include a considerable reduction in emissions, more torque and power across all engine speeds, and significantly improved fuel economy and refinement.
"With its excellent injection performance, Delphi's Direct Acting Common Rail is an attractive fuel injection system and a unique tool to meet ambitious development targets of future diesel engines and exceed customer expectations," said Detlev Schoeppe, engineering director Delphi Diesel Systems.
The new C-Class' unrivalled performance -- the application of Delphi's ground-breaking technology. The new Mercedes C250 takes advantage of Delphi's revolutionary technology to offer drivers improved engine output and torque while reducing emissions and fuel consumption.
Mercedes-Benz's completely-new four-cylinder diesel engine, named OM 651, celebrated its world premiere at the Paris Motor Show on the C Class. Ultimately it will be produced in three versions: 150kW, 125kW and 100kW -- all with Delphi Diesel CR systems.
The OM 651 is being launched first in its 150 kW version on the Mercedes C250 CDI BlueEFFICIENCY, marking the debut of Delphi's Direct Acting Piezo CR system.
To ensure the durability and robustness of its all-new power unit, Mercedes-Benz subjected the engine and fuel injection system to 100,000 hours on test rig and 10,000,000 test kilometres under conditions ranging from the desert to Polar regions. With its new generation of four-cylinder diesel engines, Mercedes-Benz is launching the first Euro 5 application and setting new standards in power output, torque, fuel consumption and exhaust emissions.
Delphi's innovative diesel technology was developed in Delphi diesel technical centres in Blois, France, Gillingham, United Kingdom, and Bascharage, Luxembourg. The C-Class' system is composed of a high-pressure pump, injectors, a rail and an electronic control unit (ECU). Employees at Delphi's technical centre and manufacturing facility in Blois are dedicated exclusively to engineering and producing injectors for advanced common rail injection systems. With a "customer-orientated" approach and employing a Quick Response Room for rapid customer response, the Delphi team relies on a unique combination of people and processes to deliver this precision product.
All key components of both families have been designed in a way that they can easily be interchanged. As such, one can switch from Fast Solenoid to Direct Acting injector technology without having to make any design change to the base engine. Pump and rail can be kept similar, and, having exactly the same packaging for both injector types, they can be interchanged without any changes to the base cylinder head.
The Balanced Valve Fast Servo Solenoid Injector family is capable of system pressures up to 2,000 bar. It is based on a unique injector design with balanced servo valve technology. The small size of this actuator allows it to be packaged in-line and in close proximity to the needle providing extremely fast actuation and precise metering.
"Because there are no significant differences in performance between Delphi's balanced valve servo-solenoid and competitors' unbalanced servo-piezo systems, Delphi's Multec servo solenoid injector is the best value solution in the market today," said Avila. "In addition, Delphi's Direct Acting delivers a unique performance/cost value proposition and a step-change in technology that provides considerable potential for further refinement."
"With the introduction of the Direct Acting diesel Common Rail technology, Delphi is able to deliver the best solution for the customers' requirements: the Balanced-valve solenoid technology offering a high-performance, cost-effective solution for the majority of vehicles and the Direct Acting piezo for demanding applications that require high fuel flow with exceptional control," added Avila.
Delphi Diesel Systems business growth
For more information about Delphi, visit www.delphi.com.