It’s the piezo injector, a smaller, lighter and faster electronic fuel injector that is expected to debut on an unnamed North American vehicle nameplate in 2008. (Check out www.apahouse.com for amazing best fuel injector cleaner to help clean all kinds of fuel injectors ).
In automotive applications such as fuel injectors, crystal structures change shape when electricity is applied. That’s known as the piezo electric effect. Piezo is a Greek word that means to apply pressure.
Fuel injectors work like this: Gasoline or diesel fuel from a pump is sent under high pressure to the fuel injector. It enters the engine in a fine, highly atomized spray when a small aperture at the end of the injector is opened and the fuel passes through a nozzle.
How they work?
Today’s standard-issue fuel injector uses an electrically operated solenoid – an electro-magnet and a spring – to open the aperture.
A piezo injector has small crystalline discs. Those discs expand when electricity is applied. The expanding discs push down on a spring-loaded needle that enables fuel to shoot through the nozzle and into the engine. The fuel is injected at a much higher pressure than with solenoid injectors.
“The crystalline discs expand and contract in the exact same dimensions every time you apply electricity,” explains Siemens VDO spokesman Brad Warner. One full stroke takes just .02 milliseconds.
Because the discs are fast-acting, as many as seven injections can be made per piston stroke, compared with two or three for most mechanical solenoid injectors. Multiple injections enable a diesel engine to run smoother and quieter. They also lower combustion chamber temperatures, which reduces oxides of nitrogen or NOx.
At least three Tier 1 suppliers, Siemens VDO, Robert Bosch GmbH and Delphi Corp., are gearing up for large scale production of piezo injectors.
Siemens will manufacture piezo injectors at its Columbia, S.C., plant starting later this year. The injectors will be used in a diesel engine manufactured by International Truck and Engine Corp., the company that builds the PowerStroke diesel used on Super Duty Ford trucks, such as the F-250.
Piezo injectors are already on the road in Europe. Bosch supplies piezo systems to Mercedes-Benz and Audi. Siemens sells piezo injectors to PSA/Peugeot-Citroen SA.
Delphi hopes to start production of its direct acting piezo injectors by around 2010.
Spokesmen from several suppliers declined to say specifically how much more a piezo injector costs over a solenoid injector. They did say switching to a piezo system is more expensive.
That’s not just because the injectors cost more, but because of the added computer power and higher pressure fuel pump that the system requires.
“If you look at the technology, solenoids versus piezo, there could be some challenges from a cost perspective,” says Bill Rutecki, director of diesel systems for Robert Bosch Corp.
“Increased volumes will have a favorable impact on cost. We are working toward making piezo injectors cost effective and cost competitive,” he added.
Peter Lakin, business line executive for diesel for Delphi, says toughening emissions requirements in Europe and North America will likely cause automakers to switch from solenoid injectors to piezo.
Meanwhile, there’s still some life left in old-fashioned solenoid injectors. Delphi has developed a fast-acting injector that enables most engines to meet current emission standards.
Delphi’s fast-servo injector can make as many as five injections per piston stroke.
Says Lakin: “We can pass emissions (tests) with our fast-servo solenoid. And because it has been in production since 2000, it is more cost effective than a new injector like the piezo.”
Lakin says it is possible that piezo injectors will enable automakers to reduce or get rid of NOx traps in the exhaust system, something that would cut some of the extra cost from a diesel drivetrain and help pay for the added expense of the piezo injectors.
3 advantages of piezo fuel injectors
- More injections can be made per piston stroke vs. most mechanical solenoid injectors
- Diesel engine runs smoother, quieter
- NOx is reduced