SFI SYSTEM


  1. FUNCTION


    1. The D-4 SFI system directly detects the intake air mass with a hot wire type mass air flow meter sub-assembly.

    2. Unlike a conventional gasoline engine, the D-4 SFI system precisely controls both the injection timing (relative to the intake or compression stroke) and injection volume. In order to correctly inject the fuel directly into the cylinders on a gasoline engine that uses direct injection (D-4), the injection timing must be precisely controlled. This control of injection timing for a direct injection engine has a similar importance to ignition timing control for an engine with conventional intake port type fuel injection. There is a significant difference between direct injection and synchronous injection that occurs on a conventional port injected engine.

    3. Based on the signals from various sensors, the ECM controls the injection volume and injection timing to suit the engine speed and engine load, in order to achieve an optimal state of combustion.

    4. To promote the warm-up of the catalyst following a cold start, this system effects lean-burn mixture control through use of a weak stratified combustion process.

    5. Weak Stratified Combustion: This process involves injecting fuel during the latter half of the compression stroke following a cold engine start. This produces a weak stratified combustion process. This process allows the use of a hotter burning lean mixture (approximately 16.0:1) when cold. The ability to run the engine on a leaner mixture when cold is due to the injection of the fuel into the compression heated air in the cylinder (injection during latter stages of the compression stroke). This raises the combustion temperature, promotes rapid warm-up of the catalysts, and significantly reduces exhaust emissions.

      A0120L5E02

    6. Homogeneous Combustion: By injecting fuel during the first half of the intake stroke, the engine creates a more homogeneous air fuel mixture. In addition, by utilizing the heat of evaporation of the injected fuel to cool the compressed air, the engine has increased charging efficiency and produces a higher power output.

      A0120KFE02
      *1 Intake (Injection)
      *2 Compression
      *3 Ignition
      *4 Combustion