Multijet-Past, Present & Future

Discussion in 'Emerging Technologies' started by Dhhawal, Aug 9, 2011.

  1. Dhhawal

    Dhhawal New Member

    Apr 26, 2011
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    The Common rail high pressure direct injection diesel fuel system was designed and initially developed by the Fiat Group in the 1980s, with contributions from Magneti Marelli and the Fiat Research Centre. It was handed over to Bosch for the final stages of development and industrial production in the early 1990s, which we now commonly refer to as Common Rail Diesel Injection Engines.

    The Past: Common Rail Diesel Injection
    JTD revolutionised diesel engine design, allowing JTD units to set new dynamic standards and compete head-on with petrol engines across nearly all criteria, whilst still retaining the core diesel values of reliability, low maintenance, reduced CO2 emissions and exceptionally low fuel consumption figures.
    In 2002, Fiat Group was awarded the prestigious Economist Innovation Award (Energy and Environment category) for its ground-breaking work in developing the ‘Common rail’ diesel technology that is now used by almost every major European car maker.

    The Present: Multijet
    The sophisticated MultiJet technology of second generation JTDs differs from its UniJet predecessor in two essential areas; the injectors and the electronic control unit.
    Within a UniJet engine, a pilot injection raises temperature and pressure inside the cylinder to improve combustion at the time of the main stroke. However, by dividing the main injection into a number of smaller injections, a MultiJet engine affords a fuller, more gradual combustion whilst the amount of diesel burnt at each stroke remains the same; thus abetting smoother, quieter combustion, reduced emissions and increased performance.
    To facilitate multi-injection, the injectors can both reduce the time lag between injections from 1500 to just 150 microseconds, and reduce the minimum quantity of fuel injected from 2 to less than 1 cu mm. In tandem, the new control unit modulates injection strategy continually to adjust to changes within three parameters; engine rpm, torque required at any given time by the driver, and coolant temperatures.
    Thus, when coolant temperature is less than 60 degrees and torque requirement low, two small and one large injection are performed. As torque demand increases, the number of injections drops to two; one small and one large. Under conditions of high rpm and high torque demand, only one injection is required, whilst with coolant temperature at over 60 degrees, emissions are minimised with one small, one large, then one small injection in the sequence.
    Hence, whilst performance is substantially enhanced, start-up times and exhaust smoke are reduced, noise levels and vibration are lowered to ensure a quieter drive and improved passenger comfort, and both fuel consumption and emissions are significantly reduced. All MultiJet turbodiesel units easily fulfil Euro 4 emissions requirements.

    The Future: Multjet II

    The Multijet injector, capable of managing up to 5 consecutive injections in the same combustion cycle, was based on a hydraulic servovalve with an unbalanced shutter that required small sealing diameters and, consequently, longer strokes.
    In the new Multijet II injector, patented by FPT – Fiat Powertrain Technologies, produced by Bosch and integrated by Magneti Marelli in its own ECU in vehicle, the shutter is hydraulically balanced, allowing larger sealing diameter with reduced shutter strokes. Thanks to this new servovalve, it is possible to control the fuel quantities injected into the combustion chamber with higher precision and speed. In such a way, it is possible to manage up to 8 consecutive injections with very accurate metering.
    In particular the shutter stroke reduced to 20µm allows reducing dramatically the minimum time interval between two consecutives injection, until zero hydraulic dwell time. With these two consecutive injections it is possible to modulate the injection rate in order to achieve a better combustion process control. This new injection mode, called "Injection Rate Shaping", results in significant benefits in terms of noise, fuel consumption and emissions reduction.
    The innovative MultiJet II servovalve allows a faster and more flexible injection events scheduling, like Injection Rate Shaping, which is the base for more and more advanced combustion control strategies.
    With Injection Rate Shaping it is possible to reduce noise, fuel consumption and, in view of the Euro 6 limits, pollutant emissions.
    Thanks to the Multijet II and IRS, the Diesel technology makes a big step towards the fulfilment of the future Euro 6 emissions standard, achieved with a combustion improvement while reducing the need of further aftertreatment devices.
  2. Deepak Raj

    Deepak Raj New Member

    Oct 16, 2012
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    Chevrolet have lit up the festival of lights this year with these ‘to-good-to-be-true’ offer…Free insurance on every Beat… How awesome is that…
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  3. galemack

    galemack New Member

    Feb 15, 2013
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    The drive pulley or input pulley is so named because it is where the power from the engine enters the transmission through the crankshaft. The driven pulley is so named because the drive pulley is what pulls it and transfers energy to the drive shaft, and then to the wheels.


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