FUNCTION
The Direct injection 4-stroke gasoline engine Superior version (D-4S) system has both direct type fuel injection, which directly injects high-pressure fuel into the combustion chamber, and port type fuel injection, which injects fuel into the intake port. The system optimally controls the fuel injectors for direct injection and port injection according to engine load.
In low to medium engine load ranges, both direct type and port type fuel injections are used together or one of them is used to create homogeneous mixed air, thus contributing to stable combustions. With this, the system achieves low fuel consumption and low emissions. In addition, in high engine load ranges, only the direct type fuel injection is used to cool down the intake air with the chilling effect of vapors in the fuel which is injected into the cylinder, improving charging efficiency and anti-knock properties.
Immediately after the engine is started in cold state, the fuel injector assembly on the port side is selected for the injection aiming at homogenizing the mixture in the combustion chamber. Next, the fuel injector assembly on the cylinder injection side performs fuel injection during the compression process in order to stratify the mixture layers around the spark plug. This formation not only enables a substantial retardation of ignition timing but also raises the exhaust gas temperature, which facilitates the warm-up of the catalyst following a cold start.
A 1-hole type high pressure slit nozzle fuel injector assembly (for direct injection) is used. Fuel is highly atomized and spread over a wide fan-shaped area from the injection hole. At the same time, the fuel is mixed with a high amount of air and injected into the combustion chamber. High performance and high engine output are achieved by circulating intake air into the combustion chamber vertically (tumble flow) to promote the mixing of fuel and air.