The primary difference between Multiport Fuel Injection (MFI) and Throttle Body Injection (TBI) lies in the location of the fuel injectors.
While both systems utilize a throttle body to meter air, the fuel delivery method differs significantly. According to the provided reference, an MFI system functions almost identically to a TBI system except the fuel injectors are positioned just upstream of the cylinder head intake port, typically one injector per cylinder.
Here's a breakdown in table form:
| Feature | Throttle Body Injection (TBI) | Multiport Fuel Injection (MFI) |
|---|---|---|
| Injector Location | In the throttle body, before the intake manifold | Near the intake port of each cylinder |
| Number of Injectors | Typically 1 or 2 | Typically one per cylinder (4, 6, or 8) |
| Fuel Distribution | Fuel is sprayed into the intake manifold | Fuel is sprayed directly at or near the intake valve |
| Air Metering | Throttle body meters air | Throttle body meters air |
In essence:
- TBI: Injects fuel at a central point (the throttle body), allowing it to mix with air before entering the intake manifold.
- MFI: Injects fuel closer to the cylinders, providing more precise fuel delivery to each cylinder.
This difference in fuel injection location leads to variations in:
- Fuel efficiency: MFI generally offers better fuel efficiency due to more precise fuel metering.
- Engine performance: MFI typically allows for better engine performance due to optimized fuel distribution.
- Emissions: MFI typically leads to lower emissions because of the precise fuel control and improved combustion.
