Final answer:
Poppet nozzles in a central multiport fuel-injected engine are opened by fuel injectors, which are controlled by the engine's electronic control unit.
Step-by-step explanation:
On a central multiport fuel-injected engine, the poppet nozzles are opened by electro-mechanical devices known as fuel injectors. These injectors are controlled by the engine's electronic control unit (ECU), which determines the timing and duration of the injection cycle based on various engine parameters. When the ECU signals the injector, it opens, allowing pressurized fuel to spray into the cylinder. The timing of the injection is synchronized with the engine's intake and compression strokes to ensure optimal mixing of fuel and air, which is critical for efficient combustion.