Rival diesel fuel-injector suppliers are fighting a technology duel to win new business as tougher EU emissions rules take effect before the end of the decade.
German suppliers Robert Bosch and Siemens VDO Automotive and Italys Magneti Marelli say injectors using piezo technology are the only way that larger diesel engines can meet future Euro 5 rules. But rival Delphi says it can improve the performance of conventional solenoid – electromagnetic – injectors enough to avoid investing in piezo injectors.
The fifth and smallest of the leading injector manufacturers, Denso of Japan, plans to continue developing both technologies.
The injector debate pits a well-
established technology being pushed toward its known performance limits against a more costly undeveloped one with perhaps greater potential.
Suppliers decline to discuss revenues from injectors, but one unit of the complex part is needed for every cylinder in a car engine. That pushes the total European injector volume beyond 80 million units a year.
Until Delphi decided to try extending the use of solenoid injectors, many industry executives expected Euro 5 standards for nitrogen oxide (NOx) and particulate emissions would force most manufacturers to switch to piezo injectors.
The initial EU proposal for Euro 5 standards called for reducing NOx emissions to 200 milligrams per kilometer from 250mg/km and particulates to 5mg/km from 25mg/km for diesel engines. But by the time Euro 5 becomes law, possibly in 2008 or 2009, the NOx limit is likely to be an even-lower 170mg/km.
If diesel-engine manufacturers want to avoid adding new, expensive systems to clean up the exhaust after combustion, they must improve the diesel combustion process. The best way to do that is with better fuel injectors. Work led by suppliers has focused on new injectors with:
- Increased injection pressure
- Multiple-nozzle injection
- Enhanced injection timing.
Siemens VDO has used piezo injectors since 2000 and believes that technology is best for meeting Euro 5 and even tougher standards in the future.
But Delphi says its latest 2,000-bar version of traditional solenoid technology works as well as piezo.
We compared piezo with solenoid type and we saw no difference, says Detlev Schöppe, engineering director of Delphi diesel systems. Our system is also 20mm more compact.
Delphis choice has surprised industry sources.
It is interesting. Cost could be the reason, especially for French carmakers that have tighter margins, says Andrew Fulbrook, manager of powertrain forecasts at CSM Worldwides office in London. But NVH [noise, vibration and harshness] could be a disadvantage.
Stefan Geiger, an analyst at consultant Global Insights London office, doubts that piezo technology is needed to meet Euro 5. He says it also could be achieved with existing technology, addition filters and adjustments to engine management systems.
The French had already taken the easy way before, fitting particulate filters rather than optimizing the diesel combustion internally, Geiger says.
Delphi says French automakers had extensively investigated traditional solenoids.
But some other OEM customers need to be convinced about solenoid advantages, Schöppe says.
Solenoid injectors are still PSA/Peugeot-Citroens primary diesel technology, says company spokesman Marc Bocque.
But we are investigating piezo technology for its direct valve control, more precise timing and metering, Bocque adds.
Denso, which has strong ties to Toyota, is looking to add more European customers. Denso will develop both piezo and traditional solenoid injector technology. It has a new advanced piezo injector with three phases and nine injector holes instead of seven.
A technology race
Both systems are likely to meet Euro 5 standards. Many believe piezo technology has an advantage for a possible Euro 6 standard expected by 2014 or 2015, but only research will definitely answer the question.
To meet stricter limits than Euro 5, [you need] more than just higher pressures, says Shinya Omi, general manager of corporate communications at Denso Europe. You need full after treatment of exhaust gases, with a NOx catalytic converter and particulate filters.
As operating pressures increase, it becomes more difficult to balance forces, such as preventing backflow of fuel at the end of the injection phase.
The solenoid system is better suited to balance such forces, says Delphis Schöppe.
Analysts see piezo technology gaining on traditional solenoids, both for diesel and gasoline, because piezo injectors work well for gasoline direct-injection engines, a growth area.
Carmakers of more expensive premium models will go for the piezo system, while the volume makers are expected to stay with cost-effective solenoid systems, says one supplier executive.
Global Insight estimates diesels current share of European car production at 47.4 percent, or 10.2 million units, growing slightly to a 48.1 percent share by 2010.
Industry sources estimate 2010 volume for piezo diesel injectors at 20 million to 22 million units, figuring it will capture 45 percent to 47 percent of the diesel market by then.
Analysts see little change in suppliers market shares, except that Siemens VDO will gain some at the expense of Bosch because of Volkswagen. When VW abandoned its proprietary unit-injector diesel system, it entered a joint venture with Siemens VDO to make piezo-type injectors.
Says Siemens VDO group spokesman Joachim Töpfer: Because of that, we will increase our market share somewhat.