Compare throttle body injection with port fuel injection systems.
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Sr. No.
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TBI system
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PFI System
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| 1 |
Fuel is injected into the center of the throttle body.
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Fuel is injected into the port
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| 2 |
TBI uses bottom feed injector
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PFI uses top feed injector
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| 3 |
Fuel injector needs to be flushed continuously- to prevent formation of air bubble.
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Fuel injector need not be flushed
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| 4 |
1 or 2 Fuel injectors are used
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Fuel injectors are equal to the number of cylinders
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| 5 |
TBI is comparatively low pressure injection (differential pressure = 0.7 to 1 bar )
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PFI is comparatively high pressure injection (differential pressure = 2 to 3.5bar)
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| 6 |
Cheaper fuel pump is sufficient to generate the required low pressure
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Costly fuel pump is required to generate the required pressure
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| 7 |
Mixture mal-distribution may occur
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All cylinders receive equal quantity and quality of air: fuel mixture.
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| 8 |
Less accurate fuel injection control gives moderate fuel economy
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More accurate fuel injection control is obtained. Therefore increased fuel economy is obtained
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| 9 |
This is a cheap system.
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This is costly system.
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| 10 |
Exhaust emission is above the permissible emission norms.
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Very low exhaust emission is achieved to meet the strict emission norms.
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| 11 |
Moderate throttle response as the fuel is injected at the throttle body and longer length of travel for fuel to enter the engine cylinder
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Better throttle response as fuel is injected on hot back side of intake valve and shorter length of travel for fuel – to enter the engine cylinder
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| 12 |
Lower power output due to lower volumetric efficiency caused by bulky injector body at the throttle body.
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Hither power output due to low resistance at intake manifold and higher volumetric efficiency.
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