There are three common methods of fuel injection timing: simultaneous injection, grouped injection, and sequential injection.
Simultaneous Injection
During the 720° of crankshaft rotation (CA) that constitutes one engine cycle, the fuel injectors for all cylinders inject fuel simultaneously-either once or twice. This method does not require signals to identify specific cylinders; consequently, the system structure is simple, and control is relatively straightforward.
Grouped Injection
The fuel injectors of a multi-cylinder engine are divided into two or three groups, with each group injecting fuel simultaneously once per cycle. While the system structure and control logic are somewhat more complex than those of simultaneous injection, this method results in less variation in fuel delivery among the cylinders.
Sequential Injection
Fuel is injected into each cylinder during the early stage of the intake stroke, following the engine's firing order. Because each cylinder requires a dedicated control circuit, both the system structure and control method are relatively complex; however, this approach ensures the most uniform mixture quality across all cylinders. This method is seeing increasingly widespread application.
