The main type of control for multi-port fuel systems where injectors open just before the intake valve is called what?

The term that best describes the main type of control for multi-port fuel systems where injectors open just before the intake valve is "Sequential multi-port fuel injection." This technology allows for more precise control over fuel delivery by ensuring that each fuel injector activates just prior to the corresponding intake valve opening.

This timing aligns the fuel injection with the intake stroke of the engine cycle, promoting better atomization of the fuel, improved throttle response, and increased engine efficiency. The sequential operation means that injectors are fired one at a time, synchronized with the engine's firing order, which optimizes combustion and performance.

In contrast, throttle body fuel injection delivers fuel to a central location before the intake manifold, which does not provide the same level of precision. Central fuel injection is less common and typically refers to older systems that do not incorporate the benefits of modern multi-port technology. Carburetor spray injection is related to older carbureted systems, which do not utilize electronic fuel injection methods at all. Therefore, the practice of sequential multi-port fuel injection represents the most advanced and efficient approach among the options, especially concerning timing in relation to intake valve openings.