Carburetors rely on atmospheric pressure and a venturi effect to draw fuel into the engine. They typically operate at pressures significantly higher than atmospheric (often 3-7 psi or more depending on the application). This higher pressure is needed to overcome the restrictions of the carburetor itself and ensure sufficient fuel delivery, especially at higher engine speeds and loads.
EFI systems, on the other hand, use electronically controlled fuel injectors that precisely meter fuel into the engine. They operate at much lower pressures, usually ranging from 30-60 psi (though this can vary widely depending on the system and application). The lower pressure is sufficient because the injectors regulate the flow electronically, whereas the carburetor relies on pressure differences. The fuel pump in an EFI system is also typically more efficient and better regulated than the mechanical fuel pump often found in carby systems.
Therefore, while there can be exceptions, EFI systems generally operate at significantly lower *delivery* pressure than carburetors, even if the *fuel pump* pressure might be higher to handle the demands of the system. The key is that the *pressure at the injectors* is the crucial difference, and this is generally much lower in EFI.
