Delphi’s powertrain technologies include multi-point injection and direct injection gasoline systems, common rail, rotary pump diesel systems in a range of capacities and, for heavy-duty diesel applications, electronic unit injectors and electronic unit pumps. Delphi was the first to develop a solenoid injector that challenges the performance of servo piezo injection systems and the first to introduce closed loop control for diesel. It has been a successful strategy that has helped the company grow steadily to become the world’s second largest supplier of diesel common rail systems, behind Bosch. Matthew Beecham talked to Dr Sebastian Schilling, engineering director, Europe, Gasoline EMS & Powertrain Products, Delphi, and Philippe Bercher, deputy director, Diesel Engineering, Delphi.
just-auto: What impact will the stricter emission rules have on your gasoline direct-injection (GDi) system business?
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Sebastian Schilling: In the past, stricter emission legislation always triggered the development and introduction of new technologies. The main driver for GDi is the reduction of fuel consumption and CO2 emissions, while maintaining or improving the engine performance. Especially while there are different competitors already on the market, it is an exciting challenge for Delphi. Delphi has a two-GDi injector strategy in order to fulfil the market demands for both homogeneous (with the Multec 10 injector) and as stratified engines (with the Multec 20 injector). T The cooling effect caused by in-cylinder evaporation significantly reduces the knocking tendency and allows an increase in efficiency of the engine via an increased compression ratio. Especially for turbocharged engines this helps to reduce enrichment requirements significantly. The compression ratio on these new GDi engines can now be increased with less knocking tendency, which leads again to very efficient engines by using the benefits of the low-end torque like diesel engines. Running the engine in lean stratified mode like diesel engines, it is possible to reduce the pumping losses and increase the thermal efficiency, enabling very low fuel consumption. In addition, any new alternative gasoline combustion system, like controlled auto ignition (CAI) or homogeneous charge compression ignition (HCCI), will need a direct control of the combustion by direct injection of fuel into the combustion chamber. So GDi is clearly the preferred solution for future gasoline engines offering a broad range of different applications.
just-auto: What are the advantages of GDi that are attracting vehicle manufacturers?
Sebastian Schilling: The main drivers to introduce GDi are a reduction in fuel consumption and improved vehicle performance. The cooling effect caused by in-cylinder evaporation significantly reduces the knocking tendency and allows an increase in efficiency of the engine via an increased compression ratio. Especially for turbocharged engines this helps to reduce enrichment requirements significantly. The compression ratio on these new GDi engines can now be increased with less knocking tendency, which leads again to very efficient engines by using the benefits of the low-end torque like diesel engines. Running the engine in lean stratified mode like diesel engines, it is possible to reduce the pumping losses and increase the thermal efficiency, enabling very low fuel consumption. In addition, any new alternative gasoline combustion system, like controlled auto ignition (CAI) or homogeneous charge compression ignition (HCCI), wi
ll need a direct control of the combustion by direct injection of fuel into the combustion chamber. So GDi is clearly the preferred solution for future gasoline engines offering a broad range of different applications.
just-auto: Are there synergies between GDi and diesel direct injection? In the injectors, pumps, sensing, control software?
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By GlobalDataSebastian Schilling: There are several synergies between diesel direct-injection systems and gasoline direct-injection systems. The GDi technology for gasoline engines is using today injection pressures up to 200 bar, while in the meantime the diesel injection systems, depending on application, are around 2,000 bar. Independent of the differences in working pressure range, there are synergies in the area of production processes, especially for injector and pump manufacturing. In addition, the sensing and the control software can offer some additional synergies following a consequent systems approach.
just-auto: Are we likely to see more applications of cheaper, ‘homogeneous’ GDi technology in smaller engines?
Sebastian Schilling: The direct fuel injection enables to operate the engine with a significant improved low-end torque compared to MPFI [Multi-Point Fuel Injection]. In combination with turbocharging, this allows gasoline engines for the first time to reduce the engine displacements and realise ‘so-called’ downsizing. In addition to increased power and better drivability, a remarkable fuel consumption benefit could be achieved. As a first step, this technology will work on a ‘homogeneous’stoichiometric basis, while later additional technology combinations, e.g. stratified, will follow in order to achieve diesel engine-like CO2 emissions. The homogeneous system will work with conventional catalyst technology which has a clear cost benefit compared to the lean aftertreatment system for stratified applications.
just-auto: How does the adoption of GDi affect the aftertreatment requirement?
Sebastian Schilling: Generally you have to differentiate between homogenous and stratified systems. For homogenous combustion, it is the same as for conventional MPFI engines based on three-way catalyst technology. Stratified systems are working under lean conditions and, therefore, it is necessary to reduce the NOx emissions with an additional special device, the so-called DeNOx-catalyst. Due to the direct fuel introduction, it is possible to use multiple injections enabling a significant quicker heat-up of the catalyst during cold start conditions. For particulate emissions generated during the combustion, it is necessary to tune and calibrate the fuel and combustion system properly so that future emission requirements, such as Euro V or Euro VI, can be met without any additional devices.
just-auto: Although Delphi has just received its first big order for GDi technology, how do you see your business growing?
Sebastian Schilling: We see our business growing very well, especially in Europe, due to the fact that our systems have several advantages for the OEMs. Beside the noise behaviour and the E85 capability, there is also the huge cost advantage especially for the stratified system which is really important enabler for that technology.
just-auto: Going forward, what are your predictions for the GDi market in North America and Europe by 2010?
Sebastian Schilling: The Delphi high performance Gasoline Direct injection (GDi) system is optimised for the increasing use of turbochargers and biofuels. There will be a rapid growth in turbo-charging as engines are downsized to reduce CO2 emissions. Moreover, we see the biofuel content of gasoline increasing, particularly in the US and Europe.
Multec GDi is ready for applications engineering today, with production expected in early 2010. Delphi predicts that about 40% of new European gasoline vehicles will be fitted with direct gas systems by 2010.
just-auto: Are you seeing any other clear trends in GDi systems emerging and/or is there anything else you would like to add?
Sebastian Schilling: Beside the Delphi GDi systems, Delphi is working on ignition systems to extend the operating range of stratified GDi and further improve fuel economy. Delphi has developed its Multi-Charge Ignition System. The system feature is a single coil-per-cylinder control system that enables multiple sparks, increased spark energy and re-ignition in the event of spark blow-out when liquid fuel is present at the electrodes of the spark plug. Since the ignition system fires multiple times in an extremely short timeframe, it ensures a robust combustion and compensation of fuel spray variations due to tolerances in the wet system. Additionally, the MultiCharge system decreases emissions at cold start and provides a smoother engine run at critical operating conditions. To get the benefit, it is important to tune the system in the right way and to optimise its application.
just-auto: Some people say that injectors using piezo technology are the only way large diesel engines can meet future Euro V rules while others say they can improve the performance of conventional solenoid – or electromagnetic – injectors enough to avoid investing in piezo injectors.
Philippe Bercher: The use of the simple term ‘piezo’ has been generating confusion in the understanding of the advantages and disadvantages of each of the injection technology options. We cannot just summarise the injector technology simply by referring to it as ‘solenoid’ or ‘piezo’ as these only characterise the type of actuation.
It is more exact to refer to two main concepts: ‘servo actuation’ and ‘direct actuation’. In servo actuation, the injector needle is moved via an electro-hydraulic circuit actuated by a valve that can be either ‘solenoid’ or ‘piezo’. In the direct actuation, the injector needle is set in motion directly by a piezo ceramic actuator.
In servo actuation, two concepts also exist: one called ‘balanced’ and the other ‘unbalanced’. Therefore, the different existing types of injectors are:
- servo solenoid unbalanced valve;
- servo solenoid balanced valve (Delphi concept in production);
- servo piezo unbalanced valve; and
- direct acting piezo (Delphi concept for the future).
The terminology confusion is due to the fact that the ‘Servo-piezo’ concept has been referred to simply as ‘Piezo’. In reality, this concept still has the injection characteristics of a servo-hydraulic mechanism and has no particular advantage with respect to the servo-solenoid with balanced valve concept.
The Delphi solenoid injector with a balanced valve gives high performances for small injection and multiple injection capability, but in addition this helps to minimise the price due to the low voltage required to activate the solenoid (only 12V when up to 150V are required by the other concepts). This injector is the solution for Euro V emissions legislation but has also demonstrated high potential for Euro VI.
just-auto: I guess the established solenoid technology is being pushed towards to performance limits against piezo solutions which, although more expensive and as yet undeveloped, has greater potential? Is cost the main reason for using solenoid technology?
Philippe Bercher: Yes, but the performance improvement achieved with the direct acting piezo injector will have a potential to reduce the aftertreatment cost. So when high emission reductions are necessary, due to more severe emissions limits, the full system cost, engine or vehicle cost would be balanced. In addition to that, the direct acting concept offers 3-4% fuel consumption improvement with respect to the other injector concepts. This is because direct acting injjection does not have any return flow. As the pressure to reduce CO2 and fuel consumption increases, this represents another key value of this technology.
just-auto: Is piezo actually needed to meet Euro V emission rules?
Philippe Bercher: No, most of the customers will use servo solenoid or servo piezo for Euro V emissions legislation.
just-auto: Are tougher emission rules in Europe slowly killing the diesel? Will the addition of particulate filters and other aftertreatment devices make the price premium for diesel too high?
Philippe Bercher: We need to look at the global picture, not only the vehicle price. Diesel still has advantages in term of fuel consumption, robustness and reliability.
