More Economical, More Powerful, Quieter: Continental Presents New Ignition and Injection Systems
Continental AG, the international automotive supplier, is equipped with a broad range of innovative system solutions for tackling the challenges of developing direct injection gasoline engines still further. An extensive package of measures for the air-fuel system and for the ignition is needed in order to meet stricter fuel consumption and particulate emission requirements, said Gerhard Böhm, head of the Engine Systems Business Unit in Continental's Powertrain Division during the Vienna Engine Symposium.Cont
Continuous Current Ignition (CCI): the reliable ignition system
In order to achieve ambitious climate change prevention objectives and to reduce fleet consumption and thus CO2 emissions in coming years, the automotive industry will increasingly have to opt for direct injection gasoline engines and lean combustion, said Böhm. These lean concept engines in conjunction with exhaust gas regeneration systems, can sometimes give rise to areas of non-homogeneous mixture in the combustion chamber, requiring greater ignition energy in order to ensure that the mixture is reliably ignited. Filling up with high ethanol content fuel also requires energy levels which rapidly push classical single spark ignition systems to the limits of their capability. Continental's CCI system offers the possibility of precisely controlling the spark duration and the ignition energy. The spark duration is set by the engine management system which can also re-energize the ignition sparks once ignition has begun to take place in the cylinder, thus eliminating any interruption to the ignition plasma; CCI even reduces the amount of wear to the spark plug electrode compared with multi-spark ignition systems. Spark duration and ignition energy are set by the control unit so that even under critical conditions – cold-starting fuel with a high ethanol content, for example – reliable ignition and optimized combustion processes are assured.
Controlled Solenoid Injection (COSI): injection system optimization
The injection system plays a major role in being able to adhere to future statutory ceilings for exhaust gas emissions. The critical factors are the precision with which the volume of fuel injected is metered, particularly in the minimum volume range, and the preparation of the air-fuel jet. A particular challenge here is heating up the catalytic converter as quickly as possible while reducing particulate formation. However, injection strategies which produce rapid catalytic converter start-up generally increase particulate emissions. Most particulates are produced during the cold-running phase, immediately after starting up. This can be prevented by multiple injection using a considerably smaller volume of fuel and high injection pressure although fuel must not be sprayed onto the cold cylinder walls. This places huge demands on the injection system; until now, only piezo injectors have been capable of metering the required three milligrams or less of fuel per injection pulse and achieving the necessary injection jet accuracy.
COSI (Controlled Solenoid Injection) now makes it possible, even using standard solenoid injectors, for a signal for minimum fuel volume to be transmitted to the control unit. A piece of software assumes control of the absolute fuel mass per injection pulse and monitors each individual injector. This prevents the injectors injecting too little fuel and the engine running erratically. In this way, COSI ensures constant precision over the system's whole service life and, as regards metering minimum fuel volumes, it brings the solenoid injector up to performance levels which have so far been the preserve of piezo injectors. The system is supplemented by Continental's recently developed high-pressure fuel pump. Thanks to its 'whispering function', the pump, which operates with a currentlessly open inlet valve, has a working noise level between one and six dB lower than comparable products from competitors.
Turbocharger with innovative wastegate: excellent ride comfort at low engine speeds
Reducing cubic capacity and the number of cylinders are two vitally important measures for lowering consumption. Smaller turbocharged engines suffer from fewer gas cycle losses, operate within a more favorable mapping range and can be run at thermodynamically high efficiency levels. There is a matching increase in their performance and torque levels. The turbocharger needs to respond very early in order for the driving characteristics to be similar to those of a large-displacement induction engine. Contributory factors in achieving this are high turbine efficiency and low wastegate losses. The bypass valve, which prevents too great a rise in the charge pressure at high loads, has to be controlled precisely and must close as tightly as possible at low engine speeds so that the turbocharger is fully effective at an early stage and is able to force the air, essential for combustion, into the combustion chambers at high pressure. Continental's electric wastegate actuator, ideally integrated into the compressor housing, increases actuating speed, and the wastegate valve, re-designed as a spherically domed disk valve, reduces pressure loss. This allows better use to be made of the exhaust gases in increasing turbine power. When the wastegate is closed, the charge pressure is greater and builds up more quickly; engine power is available earlier and therefore more conveniently for the driver.
System solutions for the optimum use of all components
The optimum coordination of all the components in the drive system from fuel supply to exhaust gas aftertreatment demands system solutions which also need to have the potential for hybrid technology to be integrated. This requires the data in the drive train to be networked. Continental's Engine Management System 3 (EMS 3) provides vehicle manufacturers with an open architecture based system which conforms to the AUTOSAR standard and which offers great flexibility when implementing new system configurations such as the incorporation of sensors. In addition, the system can be easily adjusted to the varying requirements of each individual market.
Direct injection gasoline engines: significant growth in the next few years
Whereas, most engines currently installed in vehicles throughout the world operate on the multipoint fuel injection (MPI) principle (roughly 50 percent), this proportion will drop to around 34 percent by the end of the decade. At the same time, vehicles with direct-injection gasoline engines will experience a rapid rise from around six percent at present to 32 percent. The pattern varies from region to region. Direct injection will become the dominant technology in Europe by next year and, by 2015, it is assumed that 8.4 million vehicles will have direct-injection engines installed compared with just 4.5 million with MPI technology engines. This means that in four years direct-injection engines will have around a 35 percent share of the total European market.