One of the keys to making the latest generation of diesel engines as clean and efficient as they are has been common rail injection systems and, more recently, piezo electric injectors. Continental Automotive Systems has just introduced a new type of piezo injector that may take diesels to the next level. Earlier injectors used electro-magnetic solenoids to move the injector needles allowing fuel to flow into the combustion chamber. Piezo injectors use a stack of piezo crystal plates that expand when an electric current is applied. That expansion causes the needle to move. The expansion of the piezo crystals is more precise and repeatable than the electro-magnetic solenoids allowing for more precise fuel metering for lower consumption and emissions.

Continental's new injector design takes advantage of the precision and reproducibility of the piezo crystals by adding position sensing to the needle itself. Because the position of the needle in time now correlates so well to the fuel flow rate, the potential exists to be able to eliminate other sensors that are being used to control diesel fuel systems. High pressure common rail injection systems typically use 5 -7 individual injection pulses per combustion cycle. Because the fuel flow can be measured in real time with the new injectors, the size of individual pulses within the sequence can be varied for even lower fuel consumption and emissions. Continental is claiming the new injectors help achieve a 35 percent reduction in particulate and NOx emissions. An engine optimized for these injectors could potentially meet the Euro VI (and equivalent US Tier 2 Bin 5) standards without the need for any costly NOx aftertreatment. This would help cut the cost premium between gas and diesel engines.

[Source: Continental]