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ABSTRACT

Gasoline direct injection (GDI) engine technology has received considerable attention over the last few years as a way to significantly improve fuel efficiency without making a major shift away from conventional internal combustion technology. In many respects, GDI technology represents a further step in the natural evolution of gasoline engine fueling systems. Each step of this evolution, from mechanically based carburetion, to throttle body fuel injection, through multi-point and finally sequential multi-point fuel injection, has taken advantage of improvements in fuel injector and electronic control technology to achieve incremental gains in the control of internal combustion engines. Further advancements in these technologies, as well as continuing evolutionary advancements in combustion chamber and intake valve design and combustion chamber flow dynamics, have permitted the production of GDI engines for automotive applications. Mitsubishi, Toyota and Nissan all market four- stroke GDI engines in Japan.

Major Objectives of the GDI engine

• Ultra-low fuel consumption that betters that of even diesel engines
• Superior power to conventional MPI engines

Sophisticated high-pressure injectors capable of producing very fine, well-defined fuel sprays, coupled with advanced charge air control techniques, now make stable GDI combustion feasible. There are impediments to widespread GDI introduction, however, especially in compliance with stringent emission standards. This report addresses both the efficiencies inherent in GDI technology and the emissions constraints that must be addressed before GDI can displace current spark-ignition engine technology.

In this seminar I am intending to familiarize the working of this technology, which has the capability to become the turning point in the development of diesel engine technology  

WHY NOT CARBURETTOR?

All Internal combustion engines burn fuel in air and every fuel has ideal air ratio at which it will ignite or burn as completely as possible. The challenge that faces engineers is to introduce the perfect or precise proportions of fuel and air required for complete combustion. This is commonly referred to as the stoichiometric ratio. Petrol has a stoichiometric ratio of 14.7:1(14.7 parts of air with 1 part of fuel by weight). This ratio has to be maintained under the varying engine loads and conditions. The carb earlier did this metering with its ancillaries. But the carb has its limits and though performance and economy with modern carbs were acceptable, a seamless power delivery and emissions often suffered.

Carburetor has following disadvantages
• Vapour lock
• Perfect air/fuel mixture cannot be obtained
• Lack of throttle response
• Low volumetric efficiency
• Icing – problem in aircraft engines
• Mechanical device
• Compromises on emission

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