Fuel Delivery System: From Carburetors to Advanced Injection Technologies

The fuel delivery system plays a crucial role in ensuring the proper mixture of air and fuel for combustion in an internal combustion engine. Over the years, various fuel delivery technologies have emerged, each offering its unique advantages in terms of efficiency, power delivery, and emissions control. In this article, we will explore different fuel delivery systems, including carburetors, single point injection (SPI), multi-point injection (MPI), gasoline direct injection (GDI), and the hybrid multi-point injection + GDI system.

Fuel Delivery System


┬áCarburetors were the primary fuel delivery systems used in older vehicles. They rely on the Venturi effect to mix air and fuel in the correct proportions before entering the engine’s cylinders. A carburetor uses a series of jets, valves, and a float chamber to control the fuel flow. While carburetors were simple and widely used, they lacked precise fuel control, resulting in suboptimal fuel efficiency and emissions performance. Read more.

Single Point Injection (SPI):

Single point injection, also known as throttle body injection, was an improvement over carburetors. In SPI systems, a single fuel injector is located near the throttle plate, delivering fuel to all cylinders simultaneously. The system utilizes sensors to monitor engine conditions and adjust the fuel injection accordingly. Although SPI offered better fuel control compared to carburetors, it still struggled with precise fuel distribution among cylinders, limiting its efficiency and power potential. Read more.

Multi-point Injection (MPI):

Multi-point injection systems mark a significant advancement in fuel delivery technology. In MPI systems, each cylinder has its dedicated fuel injector, which sprays fuel directly into the intake port. This precise fuel delivery ensures more efficient combustion and improved fuel distribution among cylinders. MPI systems use an electronic control unit (ECU) to monitor and adjust fuel injection based on engine parameters, resulting in better fuel economy, power output, and reduced emissions. Read more.

Gasoline Direct Injection (GDI):

Gasoline direct injection represents a significant leap in fuel delivery technology. GDI systems inject fuel directly into the combustion chamber, bypassing the intake manifold. This allows for precise control over fuel atomization and timing, optimizing the air-fuel mixture for each cylinder individually. GDI systems operate at higher fuel pressures and utilize sophisticated injectors and engine management systems to achieve improved efficiency, power output, and reduced emissions. GDI technology is particularly effective in turbocharged engines, as it helps prevent detonation and enhances overall performance. Read more.

Multi-point Injection + GDI:

The multi-point injection + GDI system combines the advantages of both technologies. It utilizes multi-point injection for low-load engine conditions, where precise fuel distribution is critical for optimal combustion. At higher loads and engine speeds, the system switches to GDI to provide the benefits of direct fuel injection. This hybrid approach allows for better overall performance, combining efficiency, power, and emissions control. Read more.


From the traditional carburetors to advanced fuel injection systems, the evolution of fuel delivery technology has transformed the efficiency, power, and emissions characteristics of modern engines. Carburetors made way for SPI, which was later replaced by MPI, offering improved fuel control and distribution. The advent of GDI revolutionized fuel delivery, providing precise control over the air-fuel mixture. The hybrid multi-point injection + GDI system takes advantage of the strengths of both technologies for optimal performance. As automotive technology continues to advance, fuel delivery systems will continue to evolve, aiming for even greater efficiency, power, and environmental friendliness.