GASOLINE FUEL DIRECT INJECTION

In recent years, legislative and market requirements have driven the need to reduce fuel consumption while meeting increasingly stringent exhaust emissions. This trend has dictated increasing complexity in automotive engines and new approaches to engine design. A key research objective for the automotive engineering community has been the potential combination of gasoline-engine specific power with diesel-like engine efficiency in a cost-competitive, production-feasible power train. One promising engine development route for achieving these goals is the potential application of lean burn direct injection (DI) for gasoline engines. In carburetors the fuel is sucked due to the pressure difference caused by the incoming air. This will affect the functioning of the carburetor when density changes in air are appreciable. There was a brief period of electronically controlled carburetor, but it was abandoned due to its complex nature. On the other hand in fuel injection the fuel is injected into the air.

GASOLINE DIRECT INJECTION (GDI)
In conventional engines, fuel and air are mixed outside the cylinder. This ensures waste between the mixing point and the cylinder, as well as imperfect injection timing. But in the GDI engine, petrol is injected directly into the cylinder with precise timing, eliminating waste and inefficiency. By operating in two modes, Ultra-Lean Combustion Mode and Superior Output Mode, the GDI engine delivers both unsurpassed fuel efficiency and superior power and torque. The GDI engine switches automatically between modes with no noticeable shift in performance. All the driver notices is a powerful driving experience, and much lower fuel bills. It's the best engine on the market. A Gasoline direct injection system consist various components as shown in the figure below.

MAJOR OBJECTIVES OF THE GDI ENGINE
v Ultra-low fuel consumption, which betters that of diesel engines.
v    Superior power to conventional MPI engines

THE DIFFERENCE BETWEEN NEW GDI AND CURRENT MPI
For fuel supply, conventional engines use a fuel injection system, which replaced the carburetion system. MPI or Multi-Point Injection, where the fuel is injected to each intake port, is currently the one of the most widely used systems. However, even in MPI engines there are limits to fuel supply response and the combustion control because the fuel mixes with air before entering the cylinder. Mitsubishi set out to push those limits by developing an engine where gasoline is directly injected into the cylinder as in a diesel engine, and moreover, where injection timings are precisely controlled to match load conditions. The GDI engine achieved the following outstanding characteristics.